|06-30-2004, 12:29 AM||#1|
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Shifting FAQ: Read if you are new to AWD or a MT
This post is meant to be an informative narrative catered toward:
a. New manual transmission owners
b. People with specific shifting problems
c. People inexperienced with the differences between an AWD car vs. a FWD or RWD car
d. People wanting more information on transmissions in general
Where can I find good background information of transmissions? A good general reference for new people as well as a refresher for more advanced users is How Stuff Works' Transmission Tutorial.
Where can I find good background information on differentials? A good general reference for new people as well as a refresher for more advanced users is How Stuff Works' Differential Tutorial. More Subaru specific information is contained on this thread.
Is shifting different with an AWD car vs. a FWD or RWD car? One has to visualize the power transfer in a car to get a better understanding. In a FWD or RWD car, if you shift or launch the car too aggressively, the excess power is transmitted to the tire(s), which will spin. Put another way, excess power is "burned off" through tire smoke. In an AWD car, if you shift or launch the car too aggressively, the excess usually isn't enough to overpower the tires' grip. In this situation, the excess power must be absorbed somewhere else in the drive train. Though some drive train shock is normal, in an overload situation, excess power is transmitted to the various driveline components, which can accelerate wear and tear.
Where are the shifting differences most apparent? Starting off in first gear and the 1-2 shift are the most common causes of driveline shock. Obviously, there is reason to shift responsibly in every gear but these are the most commonly seen problematic shifting issues.
What is the best way to learn proper shifting for the first time? This post by NASIOC member DrDRum contains some outstanding advice for the first time or novice manual transmission user.
Is resting my hand on the shifter bad? From the WRX Owners Manual: "Do not drive with your hand resting on the shift lever. This may cause wear on the transmission components". This advice should apply to every Subaru MT model. That being said, the safest course of action is to keep both hands on the wheel unless actually shifting.
What about starting off on hills? For advanced users, this is no problem. For first time or novice users, this can be a frightening and stressful experience. Until you can successfully master the art of a hill start, this is what you do:
1. Pull up the handbrake.
2. Attempt to take off as normal.
3. When you feel the car working against the brake, slowly release the brake.
Using this technique you will have a rollback free and safe start on a hill situation.
When I shift from 1st to 2nd, there is a thump sound coming from the rear end of the car. What causes this? The thump is the rear differential hitting either the cross member or the bottom of your car. This is caused by driveline shock due to aggressive driving and shifting. This type of driveline shock is a direct result of maximum acceleration. A thump from the rear end can occur with any shift, but most commonly occurs during the 1-2 shift due to it having the greatest internal transmission speed differential between first and second gear.
How to I remove the thump sound? Many people have experienced a reduction in rear differential noise by the installation of stiffer STi transmission mounts and/or differential mounts. The wisdom of this method is highly debated though. Common sense thought processes indicate that the stiffer mounts only transfer the shock to internal transmission and differential components. The ultimate cure is to modify the shifting technique where the driveline shock occurs.
How do I shift without the thump? You should wait until the point where you are no longer pressed into the back of your seat to let the clutch out on your second gear shift. As to the actual application of this technique:
1. You are in first gear, taking it to your favorite shift RPM.
2. Once you reach this RPM, let off the gas pedal and depress the clutch.
3. Shift into second. (Items 2 & 3 can be done quickly)
4. "The wait". Judge it based on your body's movement. Visualize your pelvis as the axis....when the rearward pressure of acceleration leaves your body and you feel as if you can naturally lean forward at the waist.....this is the shift point.
5. Release the clutch.
This is a shifting technique that requires some practice due to variances from car to car. Yes, it's slower, but better for your rear differential and transmission in the long run.
How do I launch properly? Launching is a technique for people wishing to drag race their cars. A good launch will give you a low 60ft time and goes a long way to wards showing off the prowess of AWD and a lower overall time slip. There are many launch techniques and you must decide on what method is best for your goals. For instance, a first time drag racer might want to use the most conservative launch to get used to the feeling and an advanced user with an upgraded transmission may side step the clutch at 6000 RPM. This article and this article both provide launching advice. Additional advice may be obtained by experienced locals, searching the forums, or by good old fashioned practice at your local drag strip.
Many feel that a good way to get a feel for the proper launch while being extremely kind to your transmission is to practice on a loose surface such as dirt or on a wet surface. Though the acceleration isn't the same, it familiarizes you with the sound, timing, and technique.
Why is it hard to go into first gear or downshift into first? The fault mainly falls on an old transmission design. This article details the design flaws and associated problems with the first gear on 2002-2006 Subaru Imprezas with the 5MT. These transmission issues have since been addressed by using dual cone synchros on the 2004+ STi, 2005+ Legacy/Outback, and the 2006+ WRX.
Many users often see a dramatic reduction in first gear or other transmission issues simply by changing their synthetic transmission fluid back to regular or by using a recommended synthetic. Many Subaru owners tend to change fluids more often than needed and use synthetics. Many synthetic gear oils designed for manual transmissions can create or enhance transmission/shifting issues in Subaru transmissions. This article provides a wealth of information on transmission gear oils.
What is the easiest way to downshift into first? Many users report great success in downshifting into first gear by using the double clutch method.
Why is it hard to go into reverse? Reverse is a straight cut gear with no synchros. This means reverse can be tricky from time to time. Problems can be grinding or inability to go into reverse. Since reverse is usually engaged as soon as the vehicle has started, the lack of fluid temperature and flow plays as role as well. Most reverse problems can be overcome by selecting a forward gear first, rolling forward slightly, double clutching, or some other technique. What works for one car may not work for another, so experiment with the technique that works best for your car. "Problems" with reverse engagement are actually common with many transmissions from many manufacturers.
What is heel/toe? Heel/toe is a shifting technique. It refers to using the toe of your foot to apply the brake, while using the heel to apply the gas. It will result in the driver's right foot (when looking down at it) to appear to be pointing left as opposed to straight up and down. Many also substitute this technique by using the left and right portions of their foot to the same effect. Though not heel/toe (more like big toe/little toe) in appearance, it serves the same function. It is usually used for rev matching during a downshift, but has other uses as well
How do I heel/toe? This depends on the user and pedal arrangement. Some users prefer to shift their right foot and use the traditional toe on brake/heel on gas technique. Others use their big toe for the brake and little toe for the gas. The use depends on the width of the drivers' foot and if the vehicle is equipped with adjustable pedals or not. Some prefer one method or can use both equally as well. Once the placement is decided upon, it can take awhile to become proficient. Practice on the street, use on the track is wise advice for those considering this technique.
When should I heel/toe? Heel/toe driving is generally reserved for road racing and those who do lots of rev matching. The average user will probably not see any benefit from using this or other advanced techniques.
What is rev matching? Matching the engine speed to the transmission input speed before re-engaging the clutch. Rev matching is both a term and a technique.
How do I rev match? Rev matching can either occur through the use of a double clutch technique, as discussed below, or through blipping the throttle while the clutch is depressed. Blipping the throttle is a term that indicates the driver revs the engine based on need while the car is in neutral or the clutch is in. Rev matching can be performed via the heel/toe technique as demonstrated in the animated picture above.
When should I rev match? Rev matching is generally reserved for downshifting. Proper rev matching ensures that a vehicle's suspension will not be upset by reapplication of power when exiting a corner. This is really an advanced shifting technique and is not required for the average or above average driver in most cases. There are those of the opinion that rev matching will save wear and tear on the clutch though.
What is double clutching? Technique for rev-matching the transmission's intermediate shaft to the output gear that is to be selected.
How do I double clutch?
1. Power is removed and clutch is disengaged (clutch pedal down).
2. Transmission is shifted from original gear to neutral.
3. Clutch is re-engaged (clutch pedal up). (Driver now has control of intermediate shaft speed by controlling engine speed).
4. Driver blips the throttle to match intermediate shaft speed to speed of new gear. (This takes practice to get the right match).
5. Clutch is disengaged (pedal down).
6. Transmission is shifted from neutral into new gear.
7. Clutch is re-engaged (pedal up) and power is applied.
Steps 1- 3 can be done casually or quickly. Steps 4 - 6 must be done quickly so that the intermediate shaft doesn't slow down again before it's engaged. If step 7 is also done quickly, the engine will also be 'rev-matched' to the rest of the driveline so that engagement will be smoother.
(The steps on this animated graphic do not coincide with steps described above)
When should I double clutch? The only instance one may need to double clutch would be during the 2-1 downshift on a 02-04 WRX. Many find this a useful technique for a smooth 2-1 downshift due to the WRX's transmission design flaw, or in any gear where there appears to be problems with the synchro. The 2004+ STi and the 2005 Legacy/Outback have different first gear synchro system and do not experience the same problems when performing the 2-1 downshift. Otherwise, this is really an advanced shifting technique and is not required for the average or above average driver in most cases. There are those of the opinion that double clutching will save wear and tear on the transmission synchros though.
What is flat shifting? In a nutshell, flatshifting is where your right foot never leaves the gas pedal. You quickly engage the clutch at the shift point, shift gears, and side step the clutch. While terrible on an OEM gearbox, this can safely and effectively be performed on some aftermarket gearboxes for improved racing times. Some dogbox transmissions also take well to another method. This method requires a slight lifting of the gas to unload the dogs, a lightning fast shift, then back fully on the gas. Though you technically can perform either of these two shifting actions in an OEM synchro equipped gearbox, it falls along the same lines as parachute packing. Yes, you can do it yourself, but it's best left to professionals.
Last edited by Unabomber; 06-07-2006 at 05:53 PM.
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