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Old 11-13-2004, 07:32 PM   #1
Unabomber
Big Ron
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Exclamation Transmission FAQ: Read if you are thinking of upgrading!

Transmission FAQ

The primary purpose of an upgraded gearset or transmission is to provide increased strength over the OEM unit or to utilize different gear ratios better suited to the particular racing style of the end user.

What is some good background transmission information?

Transmission walkthrough
Clutch walkthrough
Gear walkthrough
Gear lingo
Gear ratio walkthrough
Differential walkthrough
Subaru specific differential information
AWD information
Subaru's AWD walkthrough
Subaru's AWD walkthrough
Transmission Dictionary

What type of gears are available? There are two types of gears commonly used in transmissions based on their teeth engagement pattern.

Helical Gears: Helical gears are used in standard factory transmissions. The teeth on Helical Gears lie along a helix, the angle of the helix being the angle between the helix and the pitch cylinder element parallel with the gear shaft. Helical gears can connect either parallel or nonparallel non intersecting shafts.

Helical Gear example:


Spur gears (also known as straight cut gears): Spur gears have straight teeth and are used to contact parallel shafts.

Spur Gear example:


What are the differences between gear types? Primarily noise. Spur gears have a high pitched whining noise associated with them similar to the noise reverse gear generates. Helical gears are generally as quiet as the OEM gears. With both gear types though, the tone and volume of any additional noise can vary between manufacturers.

Which gear type is stronger? This is one question without a clear answer. The theory behind helical gears being stronger is because the contact between mating teeth increases more gradually and more teeth are in contact at a given time compared to a spur gear. So, looking at this further, helical cut gears would be stronger than straight cut gears of the same width as more than just one tooth will be transferring the torque. Helical gears have one disadvantage when compared to spur gears. When they are loaded a side thrust is created that must be absorbed in the bearings. There is also a strong case represented by spur gears as they generally have fewer, but larger and theoretically stronger teeth. It is probably best to choose the best gear type based on manufacturer ratings or noise preferences rather than gear type.

What does a Subaru transmission look like inside?



1. Mainshaft
2. Mainshaft support bearing
3. 1st drive gear
4. Reverse drive gear
5. 2nd drive gear
6. 3rd drive gear
7. 3/4 selector hub
8. 4th drive gear
9. Mainshaft thrust bearing
10. Output shaft thrust bearing
11. 4th driven gear
12. Speedo drive
13. 3rd driven gear
14. 2nd driven gear
15. 1/2 selector hub
16. 1st driven gear
17. Pinion shaft support bearing
18. Pinion
19. Ring gear
20. Stub axle
21. Front LSD

Figure notes: 5th gear is not shown in this example. It would be located to the left of items 9 and 10 in similar fashion to the other gears. Though hard to see, items 7 and 15 each contain a shift fork that actually select the gears. Between items 4 and 5 is the reverse idler gear which slides forward during engagement causing item 15 to spin the pinion shaft the opposite of mainshaft rotation. Items 18 and 19 are known overseas as the Crown Wheel and Pinion (CWP). This is noted to avoid any possible confusion if you should happen to hear/see this term at a later date.

What types of engagement are available? This is a common source of confusion when searching for information on transmissions. There are two types of engagement: Synchro and Dog.

Synchro engagement (also known as synchromesh) is what most passenger cars use.

Advantages:
a. Smooth operation on the road
b. No special driving style required

Disadvantages:
a. Synchros and shifting forks can break when abused and shifted aggressively
b. Slower to shift vs. dog engagement

Dog engagement is what most race prepared vehicles use.

Advantages:
a. Engage at any rpm
b. Allows for wider gear design
c. Will flat shift (Flat shifting is a practice where the clutch or gas do not need to be totally lifted in order to shift. Users will slightly lift one or the other to unload the dogs to allow a very fast shift)

Disadvantages:
a. Difficult to drive on the road
b. Recommended only for race use
c. Special care required under normal street use

What is a dog box? A dog box is the term for a transmission utilizing a dog engagement. A dog box can have either helical or spur gears or both.

What is a half dog box? A half dog box utilizes a combination of synchro and dog engagement. It depends on the manufacturer and customer preferences. Generally speaking, the first and second gears are dog engagement and the rest of the gears are synchro engagement. A half dog box can have either helical or spur gears or both.

What is synchronizer (synchro) engagement?
Synchros are synchronizers inside the transmission. These are the actual parts that move when you move your gear shift from side to side and back and forth. Their job is to connect the gears of the transmission to the shafts that they ride on and lock them together. This must be done at a gradual rate or the gears will grind. The synchronizer drives a cone shaped metal piece against the gear and starts the gear spinning. It accelerates it to the speed of the output shaft. When the gear reaches the speed of the output shaft, the synchro meshes completely with both of them and directs drive through its splines from the gear to the output shaft or vice versa.

What is dog engagement? Dogs are basically no more than cogs on a slider. The shifter pushes them into a receiver ring which engages the gear it is attached to. There is a separate dog and receiver for each gear in the transmission. On a racing transmission, there is a lot of "slop" (the gaps in the receiver are a lot larger than the teeth on the dog), which makes it easier to move into and out of the gears at higher RPMs without fully engaging the clutch.

Can a dog box be driven on the street? Though generally reserved for race applications, many users drive dog boxes on their daily driven vehicles. To do so, you need to learn proper shifting techniques and rev matching skills to decrease wear on the dog gears. The Shifting FAQ, this article, local personnel, or your transmission professional should be able to provide assistance with proper shifting techniques. This is one decision that should not be made lightly. If there is the slightest doubt in your mind as to your technique or attitude towards a daily driven dog box, you should opt for a synchro engagement transmission. Another thing to keep in mind is that a dog box is definitely not an option for a vehicle that sees occasional use by others such as your spouse, friends, visitors, valet, etc.

Can I get a sequential gearbox? Yes, but start saving your pennies. The Prodrive AKA WRC unit is $75,000, is lease only, and requires rebuilds every 1000 miles. KAPS has a unit for the bargain price of 22,000 Euros. Modena did make a special paddle shift sequential unit, but it is unavailable for purchase. Ikeya makes a sequential conversion kit for ~$1400 that converts the normal H pattern into a sequential pattern. SQS makes a 6MT sequential for ~$2500. MUCH thought should be given to these options though as they are unproven in the United States, probably require pricey professional installation, and they encourages faster shifting which is more damaging to gears due to the increased shock load they introduce.

What is the biggest transmission misconception? That when you shift gears, you are physically engaging the teeth of the transmission. As seen in the picture above, the teeth of your transmission are always engaged, meshed, and moving. When you shift gears, what you are doing for both dog and synchro engagement is engaging the sliding mechanism inside the gears to apply power to the selected gear. When this occurs, a load is generated in that gear and forward motion occurs.

What is the second biggest transmission misconception? Case flex occurs within Subaru transmissions. Here is how the Subaru 5MT transmission case appears removed from the vehicle:

Top view


Side view


The front transmission section houses the gears and is opened by removing the left and right half shells to expose the gears. These shells are bolted to each other as well as held in place by being bolted to the engine block and the rear transmission section which is another solid piece. Looking at the construction, it is impossible for the housing to flex.

Even if flex occurred, the gears sit on top of each other, so if flexing to any degree occurred, the gears would actually come together firmer due to gravity than apart as some contend. The premise of case flex when looked at from a construction aspect is a moot point and aside from the evidence listed here, there are any number of other reasons in the internal construction that any transmission professional can go over in further detail.

Who makes gear sets?
Andrewtech Automotive (PPG custom)
APS (link goes to a retailer as this product is not on the APS website)
Albins Off Road Gears (makers of Possum Bourne gears)
BPM (No longer sells gears)
Chalak gears were named after their designer, Haysam "Sam" Chalak and are now sold under the company he works for, PAR.
FIS
Gimmie Gears (Gears have been discontinued until further notice)
Hewland (makers of Prodrive AKA WRC gears)
Holinger Engineering
Kaaz
KAPS
MFactory
MRT Performance
Modena Engineering
PAR (Precision Automation Robotics)(makers of TRP gears)
PPG (Pfitzner Performance Gearbox)(makers of TurboXS gears)
Possum Bourne Motorsport
Prodrive
Quaife
S&J Automotive
STi (link goes to a retailer as STi does not have gears on their website)
TRP (Tony Rigoli Performance)
Zero Sports

What gear ratio choices are available?

3.636 (1st) 2.375 (2nd) 1.761 (3rd) 1.346 (4th) 0.971 (5th) 0.756 (6th) 2004-2006 STI (USDM)
3.636 (1st) 2.235 (2nd) 1.521 (3rd) 1.137 (4th) 0.971 (5th) 0.756 (6th) 2007+ STi (USDM)
3.636 (1st) 2.375 (2nd) 1.761 (3rd) 1.346 (4th) 1.062 (5th) 0.842 (6th) All years JDM STI 6MT
3.454 (1st) 1.947 (2nd) 1.366 (3rd) 0.972 (4th) 0.738 (5th) 2002-2007 Stock WRX
3.166 (1st) 1.882 (2nd) 1.296 (3rd) 0.972 (4th) 0.738 (5th) 2008/2009 Stock WRX
3.454 (1st) 2.062 (2nd) 1.448 (3rd) 1.088 (4th) 0.780 (5th) Stock RS
3.166 (1st) 1.882 (2nd) 1.296 (3rd) 0.972 (4th) 0.738 (5th) Stock Legacy GT
3.166 (1st) 1.882 (2nd) 1.296 (3rd) 0.972 (4th) 0.738 (5th) STi (Non-RA) (5 speed)
3.083 (1st) 2.062 (2nd) 1.545 (3rd) 1.151 (4th) 0.825 (5th) STi RA (5 speed)
3.167 (1st) 2.267 (2nd) 1.667 (3rd) 1.250 (4th) 0.964 (5th) Kaaz
3.180 (1st) 1.940 (2nd) 1.350 (3rd) 0.966 (4th) 0.740 (5th) Chalak (now PAR)
3.270 (1st) 2.286 (2nd) 1.667 (3rd) 1.238 (4th) 0.958 (5th) MFactory
3.180 (1st) 1.910 (2nd) 1.350 (3rd) 0.967 (4th) 0.825 or 0.738 (5th) PAR Street Perf.-Drag
2.916 (1st) 1.910 (2nd) 1.500 (3rd) 1.160 (4th) 0.920 or 0.880 (5th) PAR Rally-Track
3.000 (1st) 2.000 (2nd) 1.480 (3rd) 1.170 (4th) 0.963 (5th) Sport Gimmie Gears
3.450 (1st) 1.940 (2nd) 1.360 (3rd) 0.960 (4th) 0.760 (5th) Street Gimmie Gears
3.000 (1st) 2.000 (2nd) 1.480 (3rd) 1.170 (4th) 0.760 (5th) Sport/Street Gimmie Gears
3.454 (1st) 1.947 (2nd) 1.366 (3rd) 0.963 (4th) 0.738 (5th) APS
2.917 (1st) 2.090 (2nd) 1.556 (3rd) 1.176 (4th) 0.900 (5th) Group N Quaife
2.917 (1st) 2.090 (2nd) 1.556 (3rd) 1.250 (4th) 0.962 (5th) Clubman Quaife
3.454 (1st) 2.333 (2nd) 1.750 (3rd) 1.354 (4th) 0.972 (5th) Synchro Quaife
3.080 (1st) 2.150 (2nd) 1.350 (3rd) 1.050 (4th) 0.738 (5th) Andrewtech Automotive (PPG custom)
3.180 (1st) 1.870 (2nd) 1.320 (3rd) 0.950 (4th) 0.738 (5th) PPG SC dog
3.080 (1st) 2.150 (2nd) 1.500 (3rd) 1.050 (4th) 0.738 (5th) PPG HC dog
3.080 (1st) 1.870 (2nd) 1.320 (3rd) 0.950 (4th) 0.738 (5th) PPG SC synchro
3.180 (1st) 1.870 (2nd) 1.320 (3rd) 0.950 (4th) 0.738 (5th) PPG HC synchro
2.916 (1st) 2.090 (2nd) 1.555 (3rd) 1.176 (4th) 0.900 (5th) PPG Groupe N Rally
3.080 (1st) 1.880 (2nd) 1.350 (3rd) 0.960 (4th) Stock (5th) Stock (6th) PPG 1-4 SC dog (drag) for 6MT
3.330 (1st) 2.384 (2nd) 1.750 (3rd) 1.330 (4th) 1.040 (5th) Stock (6th) PPG 1-5 SC dog (Group N Rally) for 6MT
3.636 (1st) 2.375 (2nd) 1.761 (3rd) 1.346 (4th) 1.062 (5th) 0.842 (6th) PPG 1-6 SC dog (Group N Rally) for 6MT
MRT's gear ratios (.pdf document)

These are all the listed gear ratios for different manufacturers. Some manufacturers do not list gear ratios on their website, do not list them all, or offer custom options. Please consult with the manufacturer for their latest information.

What will my top speed, RPM @ 80 MPH be, etc. with a new gear set? You can figure this out with a high degree of precision using these two formats:
a. Web based format
b. Excel spreadsheet
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Last edited by Unabomber; 10-19-2009 at 05:52 PM.
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Old 11-13-2004, 07:32 PM   #2
Unabomber
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What steps can I take to avoid transmission failure? There are many users of stock Subaru transmissions that have heavily modified vehicles. It goes without saying that when used with the proper shifting techniques, your transmission will enjoy a long and healthy life if you learn the quirks of your transmission and modify your shifting technique to promote a long and healthy life. The Shifting FAQ and the assistance of experienced local personnel should be able to provide assistance with proper shifting techniques.

Aside from proper shifting, use of the factory clutch or an organic clutch of similar design should ease driveline shock. The clutch was conceived to be a weak, mechanically adaptable link between the engine and the transmission to protect these more vital assemblies. Upgraded clutches on a stock transmission can accelerate failure. For more clutch/flywheel info view the Clutch & Flywheel FAQ.

To a certain degree, lowering your final drive will produce more mechanical advantage at the ring and pinion gears and less at the transmission (less stress on the gearset). This can be accomplished by a final drive ratio conversion or through using smaller than OEM 24.9" circumference tires. This link and this link and this link contain calculators to determine tire heights and effective gear ratios for new tires. For example, a popular tire upgrade for the WRX is 50 series 16" tire with a 24.1" circumference. This equates to an effective final drive ratio of 4.03 over the OEM 3.90.

Another option is RWD conversion through DIY means or in the form of a purchased kit via Andrewtech Automotive, MRT, Rocket Rally, or Kingpin. Obviously this is not an option for true AWD lovers and it can create its own set of unique problems associated with additional stress to the rear driveline components. It can ease transmission stress as additional driveline forces get transmitted into tire smoke.

Can I make my Subaru RWD or FWD? RWD conversion options are detailed in the above paragraph. A FWD conversion 5MT kit is available here though it is rarely used. A FWD conversion 6MT kit is available here though it is rarely used.

How much power can a gear set take? Shock load is the PRIME indication of when a gear set will fail. Though some manufacturers/vendors advertise HP ratings, those should be taken with a big grain of salt.

What causes a gear set to fail? Shock load. Shock load is the term used to describe any amount of drive line shock, though usually associated with extreme acceleration or traditional drag strip launches. It is an incalculable forum based on power times application of power time severity of application times about 900 other variables. While many manufacturers say that their gear set can withstand XXX HP or TQ, this is merely a general indication of its strength. Any gear set is subject to failure and the key component of that failure is the number of times a shock load occurs within that gear set.

While the exact number of shock loads before failure depends on the power and type of shock load, this is what most professional racings teams do to avoid transmission failure: Carefully document and run a new transmission to failure. This can be XXX uses, hours, or other means of accountability. Once failure occurs, subtract 10% from the accountability figure and use this figure as the replacement cycle. Obviously, this figure may then be modified or scheduled maintenance and inspections may occur periodically prior to the replacement cycle. Once a schedule is set, replacement occurs prior to failure. Many professional race teams report wonderful results using this methodology.

What is the cheapest transmission upgrade? An STi gear set (RA or non RA 5 speed set), Legacy GT gearset, or another OEM gear set would constitute the cheapest upgrades. Pricing for the STi RA and Non-RA gear sets is around $1300 depending on the retailer plus possible additional costs normally found during installation and applicable installation charges. A Legacy GT or an OEM complete gear set will be around $850. It is important to note that as of March of 2002 (build date) the Subaru 5MT swapped over to RA width gears. If your transmission code is TY754VN2AA you have the narrow gears. If you have transmission code TY754VN2BA you have the wider gears. So many 2002 and some 2003 (model year) users switching to newer gears would not only get new gears, but stronger gears. All gears available through Subaru are now the newer RA width.

What about 06/07 WRX owners? Your final drive is 3.70 vs the other year models' 3.90. This in effect adds 6% more load to your gears vs. previous years. While it's impossible to calculate this into the shock load formula mentioned above, it is noted that there are an increasing amount of 06+ owners with broken gears being seen here. So shift/drive kindly, investigate increasing your apparent final drive through smaller diameter tires, and temper your power modifications based on how soon you can afford to upgrade gears.

What is cryo treatment? Simply put, it is a process of freezing parts to -300° F to improve their properties. It is a "dry" process, during which the parts are never put in contact with the liquid nitrogen. The parts are cooled very slowly and then held at a temperature of about -300° F for anywhere from 24 to 36 hours, and then brought very slowly back to room temperature. Deep cryogenic tempering creates significant increases in abrasive wear resistance and durability. These improvements may be accompanied by increases in tensile strength, toughness, and stability coupled with the release of internal residual stresses. While cryogenic treatment is primarily used to improve the properties of the material, it can also provide stress relief, reductions in stress-relief cracking, improved surface finish, and improved machinability.

What is shot peening? Shot peening is a cold working process in which the surface of a part is bombarded with small spherical media called shot. Each piece of shot striking the material acts as a tiny peening hammer, imparting to the surface a small indentation or dimple. In order for the dimple to be created, the surface of the material must be yielded in tension. Below the surface, the material tries to restore its original shape, thereby producing below the dimple, a hemisphere of cold-worked material highly stressed in compression.

Nearly all fatigue and stress corrosion failures originate at the surface of a part. Further, it has been well established that cracks will not initiate or propagate in a compressively stressed zone. Since the overlapping dimples from shot peening create a uniform layer of compressive stress at metal surfaces, the process provides considerable increases in part life. Compressive stresses are beneficial in increasing resistance to fatigue failures, corrosion fatigue, stress corrosion cracking, hydrogen assisted cracking, fretting, galling and erosion caused by cavitation. The maximum compressive residual stress produced just below the surface of a part by shot peening is at least as great as one half the yield strength of the material being peened.

Shot peening increases the lifespan of treated metal components by ~20%.

How much are brand new, fully assembled 2005 OEM transmissions?
Ratios verified via SOA on 11/19/04 and all prices are retail with no discounts:
WRX transmission 32000AG970 $3111.92
3.454 (1st) 1.947 (2nd) 1.366 (3rd) 0.972 (4th) 0.738 (5th) WRX FD 3.90
(Front 3.9 center 1.1 rear 3.54)
RS transmission 32000AH000 $3111.92
3.454 (1st) 2.062 (2nd) 1.448 (3rd) 1.088 (4th) 0.780 (5th) RS FD 3.90
(Front 4.11 center 1.0 rear 4.11)
FXT transmission 32000AG820 $3111.92
3.454 (1st) 2.062 (2nd) 1.448 (3rd) 1.088 (4th) 0.780 (5th) FXT FD 4.444
(Front 4.44 center 1.0 rear 4.44)
Legacy GT transmission 32000AG780 $3111.92
3.166 (1st) 1.882 (2nd) 1.296 (3rd) 0.972 (4th) 0.738 (5th) Legacy GT FD 4.11
(Front 4.11 center 1.0 rear 4.11)
Outback XT
3.454 (1st) 1.947 (2nd) 1.366 (3rd) 0.972 (4th) 0.738 (5th) XT FD 4.444
(Front 4.44 center 1.0 rear 4.44)
STi transmission 32000AH150 $4994.83
3.636 (1st) 2.375 (2nd) 1.761 (3rd) 1.346 (4th) 0.971 (5th) 0.756 (6th) STi (USDM) FD 3.90
(Front 3.90 center 1.0 rear 3.90)
Total cost for 5 gears and the main shaft for a WRX transmission is $864.76. Broken down they are as follows: 1st $173.85, 2nd $147.22, 3rd & 4th $240.98, 5th $113.43, and shaft $189.28.

What's involved with swapping from a 5MT to a 6MT? You will need to obtain and install the following components:
1. A complete 6MT transmission.
2. 6MT transmission mount.
3. 6MT clutch fork.
4. 6MT shift knob, 6MT shifter linkage, and 6MT shift boot.
5. The drive shaft from a 6MT or the drive shaft from any model automatic transmission equipped Subaru. The stock WRX 5MT drive shaft may also be modified (will need to be shortened) to fit as well.
6. New rear end options:
a. New ring and pinion gears to upgrade the stock WRX R160 rear differential to 3.90.
b. Convert the 6MT center differential from 1.0:1 to 1.1:1 and use the stock WRX R160 rear differential.
c. Swap out the stock WRX R160 rear differential to a stock STi R180 rear differential.
The real decision to a 6MT swap is the rear differential, as going with the R180, though the "better" choice, raises the costs significantly as you need to use the entire rear end consisting of the STi driveshaft, STi rear half shafts, Sti rear hubs, and STi rear discs to include the Brembo brakes. This will also require the use of 17" wheels as well to accomidate the bigger brakes, which for some, may be an additional expense. As well, www.gearboxtech.com sells the parts that let you use R180 inner CV joints and the R160 outer CV joints if you want to use the R180 rear end and not swap over to the R180 hubs/brakes.

This thread provides additional 6MT swap help.

If I get an upgraded gear set, what other transmission related upgrades might I consider? Upgraded clutch, new flywheel, different final drive ratio, upgraded limited slip differentials, stainless steel clutch line, short shifter, shifter bushings (front, rear, pivot, linkage), rear diff bushings, subframe lockout bolts, outrigger bushings, and a new rear differential are all driveline components worthy of upgrade while your vehicle is down and the gear box is open.

How hard is it to install a gear set? Professional installation, depending on your area, should run $600-$700 on a removed transmission. Removal/replacement from your vehicle should run an additional $450. Arguably the most important step in the process of upgrading your transmission is the final assembly. This is one vehicle modification that should only be accomplished by a transmission professional with a clear understanding of Subaru transmissions and special techniques and instructions that come with most gear sets. Additionally, for correct installation, the technician needs the Subaru Factory Service Manuals and specialized Subaru use only transmission tools for perfect alignment. If the shop does not have these items, find a place that does.

Are there any hidden costs with a transmission installation? Yes. While the gear box is open, the technician may require/recommend additional parts to be installed. Some of these additional expenses can be figured prior to installation, some may crop up once the transmission is opened. Some gear sets may need additional parts as well. For example, some dog box transmissions should/must have new shifting forks or a shifter interlock. These parts can total as much as $1000. Total cost depends on your gear set and manufacturer/installer recommendations.

What questions should I ask of a gear set manufacturer or retailer?
1. What gear ratios do you offer?
2. Do you offer custom ratios or custom gear sets?
3. Are there any modifications to the case in order for your gear set to fit?
4. What is the warranty on your gear sets?
5. What other recommendations do you have?
6. How much "oops money" should I factor into my purchase in case other parts are needed?

What are common causes of transmission failures on vehicles with upgraded gear sets/transmissions? While there is no perfect answer to this, searching for failure issues can lead you to the following conclusions:
a. Installation errors.
b. Lack of recommended upgrades (broken stock shifting forks).
c. Driver inexperience.

Any other good articles on gear sets or related information? These articles may provide additional helpful information:

Subaru Barking Box
PAR's transmission FAQ
Upgraded rear differential
Upgraded final drive ratio
Mike Shield's transmission notes
.pdf about shot peening

Editors Note

This post was created because I wasn't able to find a good transmission FAQ. I came up with the text based on LOTS of searching here. Upon reading this you should have an idea of whether a transmission upgrade best suits your needs or not. The manufacturer is up to you.

My thanks to Brett Middleton from MRT, Geoff from CTI-Distributing, Paul Guard (gearguy) from Guard Transmissions, the Metal Improvement Company, and most importantly, Andrew Yates from Andrewtech Automotive for providing valuable assistance in the formulation of this FAQ and for shedding some light on the world of transmissions.

If you find an error in this FAQ, please PM me with factual details and I will update this post. Responses such as, "I have XXX's gears and they're great!" or "XXX's gears broke after 1 month" are not appreciated here, that is what the Car Parts Review Forum is for.

Last edited by Unabomber; 04-26-2011 at 10:11 PM.
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Old 11-13-2004, 07:41 PM   #3
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Awesome post, as always Unabomber. Looks like I've got some bedtime reading.
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Old 11-13-2004, 07:41 PM   #4
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this should be a sticky
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Old 11-13-2004, 08:26 PM   #5
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Mr Bomber I take my hat off to you again. Great work.

Possibly a little typo crept in at para #3:

Quote:
What are the differences between gear types? Primarily noise. Spur gears have a high pitched whining noise associated with them similar to the noise reverse gear generates. Spur gears are generally as quiet as the OEM gears.
-> should be "helical"?
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Old 11-13-2004, 08:30 PM   #6
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Yep, got my spurs and helicals confused, thanks.

Last edited by Unabomber; 11-14-2004 at 12:53 AM.
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Old 11-13-2004, 11:42 PM   #7
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Good work Ron
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Old 11-14-2004, 09:22 PM   #8
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Ron, you are the man, a true Gear Head!
AWESOME work!
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Old 11-16-2004, 12:33 AM   #9
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Lots of places resell others gearsets. Some of the places you listed are resellers not makers.

Gimmie Gears sold Possum Bourne gears
Kaaz is discontinuing 5mt gear set production according to Dave at RalliSpec
TurboXS sells PPG gear boxes
If I am not mistaken, S&J sells PPG gears
If I am not mistaken, BPM sold Chalak gearsets
Albins Off Road Gears and Possum Bourne Motorsport are the same place

If you are listing resellers, then include http://www.xcceleration.com/engine-packages-trans.html as they sell PAR boxes. Lots of them. Those, MRT and anything Possum Bourne cuts are the short list. IMHO. Possum Bourne has been cutting teeth for Porshce racing gear boxes since I can remember. I would bet they have Le-Mans wins. I would not be suprised if they cut teeth under contract for Quaife or others.

There is a video floating around that shows a 5mt flexing and then "exploding". Now, I have never seen it, but DonwShift1 mentioned he has seen it.

Now, if there is any flex, it is not confirmed or disproved, it would be do to the input shaft. In my opinion which is just an opinion. Here is the hypothesis.
The flex, so the theory goes, is casued by the long unsupported shaft. If that shaft is bent, or twisted as it were, with no relief, with the helical gears, the effect would be to flex the case where the gears are and casue improper tooth engagement. People think the case is twisting or something. It is not. If there was any flex, it would be from internally flexing wobble unsupported shaft. So goes my... um I mean the theory. Additional ribbing would help. Like the new Legacy 5mt. Hmm.

In my opinion, mind you , opinion, Straight cut is stronger. There is a reason actual race cars use straight cut gears. They are stronger when being purpose built. Built for strength with no compromise that is. Helical by nature, is a compromise solution. That is not to say they can not be made strong. Look at the 6mt. The 6mt and the 5mt gearsets are apples and oranges however. Look at a straight cut 6mt gear set compared to the OEM 6mt helical set or straight cut 5mt gear set compared to the RA or APS helical set for example. Overall contact patch is just bigger. Plus beefier teeth and and no side loads.

The helical side loads are enormous. The reduction in tooth count coupled with increased toooth size is a SUBSTANTIAL benifit. I have compared RA gearset, which is much larger than OEM to straight cut gears. The RA teeth looked anemic. Almost like they belonged in a lawn mower, in comparison. Made properly of course. MRT used to warrant thier gearsets against failure. Even in competition. They probably still do. This is nice to know for those looking for a guarantee. Interestingly, MRT states thier dog boxes are stronger than the Syncro boxes. I presume it is becasue the gears are just larger and presumably stronger. Yeah, I am not sure there is even a debate on this one with strength between the 2 sets. But what do I know.

Now, I did talk to Possum Boprne and MRT about gearsets 1 1/2 years ago. They both said purpose built straight cut is stronger by far. They pointed out that straight cut dominates motorsports. Now perhaps I heard wrong, so, let's call it my opinion and feel free to disagree and discount everything I said.

Those Gimmie gears (Possum Bourne) were superb helical gears. They did not get any better for helical gears. The currency rates as of this writting made the purchase difficult, as with all Aussie gears. I remember when they were $2500 or so.

Here is a good old post from MRT themselves.http://forums.nasioc.com/forums/show...&pagenumber=10

Sure does seem fun to drive a dog box huh! Man is a dog box tempting. I bet it would get old though. oop. Time to go search for dog box posts and reviews.

Lots and lots and lots of work in that post. Thanks for the effort. Diplomatic too.

Last edited by ebeck; 11-16-2004 at 01:22 AM. Reason: type on Possum Bourne
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Old 11-16-2004, 05:46 PM   #10
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I could add a few more definite manufacturers to your/my list, but I don't want to step on any toes. So far, I only added the commonly known ones, but you covered some others.

As to the flex issue....I've heard many stories on the forums. What sold it for me was seeing it with my own eyes. I attempted to describe it above, but that is only 50% of the issue as many of the other items are too hard to put into words without seeing first hand. Andrew "forced" me into driving up to MD for that reason. Now I won't be one of those know it alls, but I will say that after seeing a Subaru transmission with my own eyes and seeing how it all goes together, it is a moot issue. If anyone has proof otherwise, I'll be glad to look at it. Until then, I consider the case flex issue to be reason #234 why someone's transmission blew up and it wasn't their fault.

With respect to the gears, that's a real toughy. Which is stronger is a rough one as no one knows. If I was a drag racer, I'd go with spur gears. If this was a stronger daily driven car, I'd go with the helicals. Either one would be a zillion percent stronger than the OEM helical gears though. And as Brett states so elloquentily in the post you quoted: "Bigger is not always better, dont be mislead by companies that show double the width gears to make you think they are strong, is the material and TOOTH profile that effects the strength. (A F1 gear is narrower than a Std Subaru gear!)" Wow....I think I just learned something.

I very much appreciate your input and thanks for your thanks. I alway think the last FAQ was the worst, and this one is no exception as it probably took 30-40 hours to do the research and write up. This one included a road trip and extensive emails back and forth to Australia, so it was a little more intensive than the others.
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Old 11-21-2004, 02:08 PM   #11
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I see you got it on, great write up! Dont think its terrible, its just a bunch of debatable questions, it really covers the basic newbie questions, and isint that the point of this? Anyways, I'm glad to be atleast a little bit of help.

Last edited by Trunk_Monkey; 11-21-2004 at 02:16 PM.
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Old 11-23-2004, 02:29 PM   #12
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Extremely informative!! Thanks again for all your input on our (us ignorant, lazy sods) behalf!!
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Old 12-01-2004, 09:02 PM   #13
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Quote:
Originally Posted by Unabomber
STi rear discs to include the Brembo brakes. This will also require the use of 17" wheels as well to accomidate the bigger brakes, which for some, may be an additional expense.
What about the option of using the older non-brembo 2-pot rears that work with 16" wheels?
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Old 12-01-2004, 09:13 PM   #14
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That, I'm honestly not sure of. I'd have to ask around and hopefully come up with an answer. I'm sure some crafty people have done it as I heard rumors that in Australia, they don't use the Brembos, but rather mod/fabricate the OEM brakes to work on the bigger rotors???
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Old 12-08-2004, 08:51 PM   #15
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I guess I should have remembered to check this thread again. I'm not sure what you're refering to but I'm talking about the Subaru 2-pots that use 290x18 vented rear rotors and came on cars originally equipped with R-180 rear diffs. For an example see the first post in this thread:

http://forums.nasioc.com/forums/showthread.php?t=580006
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Old 12-09-2004, 12:59 AM   #16
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Hi there, just letting you know that the older type rear 2 pot brakes can be used as an option. They have exactly the same mounting points as the Brembo rear calipers, so if you are swapping the whole rear end (diff, hubs, backing plates etc...) they will bolt directly onto your new backing plates
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Old 12-27-2004, 01:30 PM   #17
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Visual 5mt and 6mt comparison by the way. http://forums.nasioc.com/forums/showthread.php?t=678591
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Old 12-28-2004, 08:43 AM   #18
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Is there a place that sells or make FD gears front and rear for the STI.

I know you can get the rear FD from Nissan motor sports for the rear. I am looking at 370s as I am trying to make my gears longer. They sell gears for the R160, R180 and R200.

I also know that the R200 and R180 is swapable in the Nissans and becasue Fuji Heavy Industries makes the diffs for these cars the Subaru should also be interchangable just incase anyone has broken a R180.
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Old 12-29-2004, 12:35 AM   #19
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You'd have to call Rallispec with your question. I would assume you can just use higher Subaru F/D gears as I believe they are physically the same size, just with different numbers of teeth on the gears. I'm taking a wild stab here, but Rallispec should know for sure. If you find out, PLEASE post back here.

Thanks for the link ebeck. I will eventually add it to the main body of my post as I have a few other things to add as well.
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Old 02-14-2005, 12:32 PM   #20
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I have a JDM Sti 6 Speed gearbox (It as 5th and 6th gears shorter than other models).
I am going to upgrad with electronic Diff and Suretrac front Diff.
I know someone are making a electronic device to work with it, instead of the original wiring loom(That I donīt have) that works realy well on rally cars.
Does any one knows about this device?
It is to dificult to find a Subaru original wiring loom for this gearbox?
Rui Torres
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Old 03-07-2005, 02:44 PM   #21
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Wow, I just found this FAQ, very nice, once again, thanks Unabomber.
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Old 03-24-2005, 11:20 AM   #22
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Just a usage log. I've been back here to this page about 20 times in the last couple months.
Thanks again Ron.
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Old 03-24-2005, 01:18 PM   #23
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Old 04-26-2005, 05:04 PM   #24
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do u know any links for a automatic to manual swap on a 04 wrx?
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Old 04-28-2005, 06:13 AM   #25
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what's the password for the gearing speadsheet? I want to change some values on there and it is password protected.
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