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Old 02-04-2011, 05:40 PM   #1
sawtooth
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Default 914 conversion, 2.5 n/a with subaru 5mt

I've been absorbing some very helpful info hear for a while and it's really helped me get my 914 conversion finished, thanks nasioc! I wanted to share the results. Special thanks to Matt Monson for helping me get educated and keeping me pointed in the right direction.

My car is a '73 Porsche 914 with a 2000 2.5 n/a sohc motor, el header, custom intake, and lightweight flywheel, plan on doing cams in the future. This motor in this car is more fun than I can describe. I really wanted to keep the 914 sports car feel, and not turn it into a muscle car with a v8 conversion. It's got more power and quick response than I could have hoped for. Equally as fun in the conversion is a '93 subaru 5mt awd transmission converted to fwd. Much easier shorter smoother shifts than the porsche 901 transaxle, and upgrade/rebuild options are much more affordable.

Here's a few pics:





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Last edited by sawtooth; 02-04-2011 at 06:13 PM.
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Old 02-04-2011, 07:48 PM   #2
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Thats what I would have done for the transmission too. Did you put an LSD in instead of the open diff?
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Old 02-04-2011, 11:16 PM   #3
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Looks pretty cool, it would be great if you posted a vid of it doing what it does.

Edit: the casual "looks pretty cool" is to hide my jealousy

Last edited by etothen; 02-04-2011 at 11:56 PM.
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Old 02-04-2011, 11:46 PM   #4
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Very nice install. Show some more pictures! I agree that this forum rocks. It has helped me solve many issues with my Meyers Manx with 04 STi on a 930 transaxle.
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Old 02-05-2011, 01:00 AM   #5
sawtooth
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Quote:
Originally Posted by Kostamojen View Post
Thats what I would have done for the transmission too. Did you put an LSD in instead of the open diff?
Cool so you think its ok to be using a non-wrx trans? I've been told a few times that the legacy trans might not hold up well. I figure that the 914 is so light, it should hold up ok to the power I can make with the 2.5 n/a.

No LSD yet, but I plan to go with OBX when I rebuild the trans. Currently it sounds to me like it has a bearing going out on the main shaft possibly, and the differential has a pretty good whirring sound when you back off the throttle. Good time to put an LSD in. I don't know much about the internals of the subaru trans yet, but I want to learn to do the rebuild myself. I bought this trans for next to nothing so I wasn't expecting much. I was thinking about picking up another from a 95 outback and doing the rebuild on it, then swap.

Last edited by sawtooth; 02-05-2011 at 04:40 PM.
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Old 02-05-2011, 01:01 AM   #6
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Quote:
Originally Posted by etothen View Post
Looks pretty cool, it would be great if you posted a vid of it doing what it does.

Edit: the casual "looks pretty cool" is to hide my jealousy
Thanks, video on its way.
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Old 02-05-2011, 03:28 AM   #7
sawtooth
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Here's a short clip of me just putting around in town. Lets you hear some of the exhaust note which i'm really happy with. I figure since it's not in a subaru I can get away without too much EL header bashing from the suby crowd. IMHO it really sounds more like a porsche should. Anyway, in case you are wondering while watching the video I'm using the gps for speedometer for now.

.

Last edited by sawtooth; 02-05-2011 at 04:47 PM.
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Old 02-05-2011, 04:40 PM   #8
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Excellent! Well done!

I think your Legacy trans will hold up fine since it won't have the stress of holding the torque through all 4 wheels and moving a barge (by comparison).

Jay
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Old 02-05-2011, 06:55 PM   #9
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Quote:
Originally Posted by sawtooth View Post
Cool so you think its ok to be using a non-wrx trans? I've been told a few times that the legacy trans might not hold up well. I figure that the 914 is so light, it should hold up ok to the power I can make with the 2.5 n/a.
I could be wrong, but I don't think there have been any real substantive changes to the 5MT over the years to make it stronger, particularly the N/A versions, so I think it should be just fine. As you said, the car is so light that the stress on the drivetrain is an order of magnitude less than it would be in a 3400# AWD Legacy or Outback.

The audio is a little rough in the video clip, but from what I can tell the exhaust sounds pretty damn good!

Quote:
Originally Posted by sawtooth View Post
I was thinking about picking up another from a 95 outback and doing the rebuild on it, then swap.
Why a '95 Outback? Is there something special you're looking for?

I believe that the ratios you've got now (from a '93 AWD 5MT) are:
AWD Manual Tranny:
1 - 3.545
2 - 1.947
3 - 1.366
4 - 0.972
5 - 0.780
R - 3.416
differentials are 4.111

I'm not sure exactly what ratios a '95 Outback would have, but I think they'd be pretty close to those (if not exactly the same). My '97 Legacy 2.5GT has slightly different 2nd-4th (2.111, 1.448, 1.088), but 1st, 5th, reverse and the diff ratio are the same as what you've got.

There's quite a bit of cutting-and-pasting you can do to tailor the gear ratios to what you want. For instance, the base model 2.2L Legacy in '97 had the same tranny as my 2.5, but had 3.900:1 final drive instead of 4.111:1. I believe there are also 3.700:1 ring-and-pinions for the 5MT, and going the other way there are 4.44:1 sets. So, you could change things up quite a bit in either direction.

I imagine the car's pretty quick already with 4.11s, but you could do 4.44s to make it even quicker in 1-4, then put in a WRX 5th gear (0.738) and end up with your highway cruise RPM only being ~100rpm higher.

Last edited by Patrick Olsen; 02-05-2011 at 08:06 PM.
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Old 02-05-2011, 10:02 PM   #10
sawtooth
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Here's a few more pics:

Fits very nice in the engine bay with lots of room to spare. Pretty cool because the Suby H4 is reminiscent of the original Porsche H4, just add water.








Suby CV with porcshe re-splined axle.

Last edited by sawtooth; 06-27-2011 at 04:24 PM.
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Old 02-05-2011, 10:51 PM   #11
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Quote:
Originally Posted by Patrick Olsen View Post
I could be wrong, but I don't think there have been any real substantive changes to the 5MT over the years to make it stronger, particularly the N/A versions, so I think it should be just fine. As you said, the car is so light that the stress on the drivetrain is an order of magnitude less than it would be in a 3400# AWD Legacy or Outback.

The audio is a little rough in the video clip, but from what I can tell the exhaust sounds pretty damn good!


Why a '95 Outback? Is there something special you're looking for?

I believe that the ratios you've got now (from a '93 AWD 5MT) are:
AWD Manual Tranny:
1 - 3.545
2 - 1.947
3 - 1.366
4 - 0.972
5 - 0.780
R - 3.416
differentials are 4.111

I'm not sure exactly what ratios a '95 Outback would have, but I think they'd be pretty close to those (if not exactly the same). My '97 Legacy 2.5GT has slightly different 2nd-4th (2.111, 1.448, 1.088), but 1st, 5th, reverse and the diff ratio are the same as what you've got.

There's quite a bit of cutting-and-pasting you can do to tailor the gear ratios to what you want. For instance, the base model 2.2L Legacy in '97 had the same tranny as my 2.5, but had 3.900:1 final drive instead of 4.111:1. I believe there are also 3.700:1 ring-and-pinions for the 5MT, and going the other way there are 4.44:1 sets. So, you could change things up quite a bit in either direction.

I imagine the car's pretty quick already with 4.11s, but you could do 4.44s to make it even quicker in 1-4, then put in a WRX 5th gear (0.738) and end up with your highway cruise RPM only being ~100rpm higher.
Thanks for all the great ideas on gears, exactly what I needed. Where do you get gears from? Find the part numbers and buy oem?

The '95 outback trans was a thought mainly because it was easily available and appears to have the same gear set. I could pick it up for $150 with hopes that it is much quieter than the one I have now. Then someday down the road do a rebuild and possibly an OBX LSD.

Here's another video without the background music so you can hear the whine in my current trans. I made a post in the transmission forum hoping to get some feedback on what I'm hearing vs. what it should sound like. Basically it sounds like an old truck, I think its the differential that is whining pretty loud. Better off to start with another trans, or rebuild this one?

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Old 02-05-2011, 11:29 PM   #12
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cool project
i have another 93 5mt you can have for free just come get it (SE boise) although it also wines ..
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Old 02-05-2011, 11:42 PM   #13
sawtooth
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Quote:
Originally Posted by Jaxx View Post
cool project
i have another 93 5mt you can have for free just come get it (SE boise) although it also wines ..
Thanks it is too much fun. Cool, you are in Boise. So tell me more about your trans. Did you figure out what was making the noise? Did you replace it with a rebuilt or ?? If you replaced it, is your new one quiet. Basically I need to find out if the older ones are just noisy no matter what, or if it can be cured with a rebuild. If the older ones are all whiners, then what year should I pick up instead?
Thanks!
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Old 02-06-2011, 02:33 AM   #14
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What was done to convert the trans to 2wd? If different "transfer gears" were installed, they may be the source of the whine.

FWIW, the 5MT FWD trans uses a solid driven shaft instead of the hollow "shaft-within-a-shaft" of the AWD trans. Should be stronger for your setup.

If you think the exhaust sounds good now, you should try a Borla replica. The blatty growl would make you consider removing your radio.....

Jay
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Old 02-06-2011, 02:54 AM   #15
sawtooth
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Quote:
Originally Posted by Storm View Post
What was done to convert the trans to 2wd? If different "transfer gears" were installed, they may be the source of the whine.

FWIW, the 5MT FWD trans uses a solid driven shaft instead of the hollow "shaft-within-a-shaft" of the AWD trans. Should be stronger for your setup.

If you think the exhaust sounds good now, you should try a Borla replica. The blatty growl would make you consider removing your radio.....

Jay
Bremar makes a conversion kit for awd to 2wd for mid engine cars. I custom built something similar to their kit. Basically its a locking nut/spool that connects the two shafts together. I'm pretty certain that's not the issue because the output shafts don't spin when tranny's in nuetral. I can still hear the whine when get up to speed and then coast in neutral. After doing a bunch more research, I'm thinking it's got to be the differential bearings.
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Old 02-06-2011, 04:47 AM   #16
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Quote:
Originally Posted by sawtooth View Post
Cool so you think its ok to be using a non-wrx trans?
There is not really any difference. Unless you go with some sort of upgraded gear set (RA, PPG, etc.)

BTW, my transmission wines like that too, and its from a late 90's something, I forget what (Legacy maybe? not sure, maybe an RS, but its not from the same car the 2000 RS motor is from).

Last edited by Kostamojen; 02-06-2011 at 04:53 AM.
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Old 02-06-2011, 10:02 AM   #17
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mine has/had 180k on it. when i got a new motor i replaced it with a 4.44

found this
http://www.bremarauto.com/products/s...onversion-kit/


and a how to for free (just realized dean posted in this thread)
http://www.914world.com/bbs2/index.php?showtopic=104513


after looking at the pictures again you need a 2.5 badge

Last edited by Jaxx; 02-06-2011 at 10:13 AM.
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Old 02-07-2011, 05:10 PM   #18
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Quote:
Originally Posted by sawtooth View Post
Thanks for all the great ideas on gears, exactly what I needed. Where do you get gears from? Find the part numbers and buy oem?
The only gear swapping I've ever done was putting an Outback 5th gear into my old 5MT so that the car would pull on the straights better at track days. (Outback 5th was 0.871 compared to 0.780 for the 2.5GT). In that case it was just a matter of getting the OEM part. I was having new front and center diffs installed, so I had the shop do the 5th gear at the same time. (And the trick worked - I picked up 8-10mph on the two long straights at VIR.)

For your case, I guess it would kind of depend on what you think you want to do with the gearing. If, for instance, you decided you wanted that 4.44:1 final drive + WRX 5th gear I mentioned - I would guess that buying an older transmission (for instance, your $150 example) and installing new ring/pinion and the WRX 5th gear along with the OBX diff would be cheaper than trying to source a tranny that already has the 4.44 gears in it. (AFAIK the only 5MTs that have the 4.44 gears are the Forester turbo models, so the trannys will be newer harder to find and thus more expensive.) Like I said, though, that's just a guess - I haven't really priced out decent used transmissions or transmission rebuild parts.

Quote:
Originally Posted by sawtooth View Post
The '95 outback trans was a thought mainly because it was easily available and appears to have the same gear set. I could pick it up for $150 with hopes that it is much quieter than the one I have now. Then someday down the road do a rebuild and possibly an OBX LSD.
For $150 I think my vote would be "can't hurt to try it!"
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Old 02-08-2011, 11:05 AM   #19
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Hey Dean after exchanging some emails on the 914world. I am here to learn from the suby folks here. Thanks for all the good tips. I hope to see you soon to get those conversion parts too!
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Old 02-08-2011, 01:49 PM   #20
sawtooth
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Hey Jamie, good to see you on the other side of the world here at nasioc! Great bunch of people with lots of good info to learn from.
- Dean
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Old 02-09-2011, 10:10 AM   #21
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Wow, great job! I have been wondering what to do with my WRX, re-build or a conversion. This looks like a fun option!!
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Old 02-12-2011, 06:35 PM   #22
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Could you comment on your shift linkage? That is a remarkable conversion.
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Old 02-13-2011, 11:35 PM   #23
sawtooth
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I built a cable shifter setup using an MR2 shifter, heavy duty push/pull cables, and a custom bulkhead bracket at the transmission.


This show's a little bit of the transmission end of the cable shifter setup. I need to get some more specific pics of bracket and cables back there.

Last edited by sawtooth; 06-27-2011 at 03:48 PM.
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Old 02-13-2011, 11:57 PM   #24
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I am planning on doing a conversion basically the exact same as you this summer. I too would be interested in seeing how the shifter was set up. Right now your pictures don't work though... I like how you have the car set up though and it's making me want to start my conversion much sooner
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Old 06-27-2011, 04:10 PM   #25
sawtooth
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Since my last update I ended up with a new motor and trans, a lot of body work and full repaint. Here is what it looks like now...

Picked up a great deal on a long block built by xcceleration. Heads are worked over and medium stage cams. They tell me it should easily be 50hp over stock. Haven't had it on a dyno yet but it does feel much stronger than my last stock 2.5, plenty of n/a power for me.









Just got back from our 914World club event in Medford. First time for me and the car at an autocross event. It was an absolute blast. The car performed well, no poblems. The n/a power band was fantastic for the course. I'll definitely be doing some more ax for fun in the future.

Last edited by sawtooth; 06-27-2011 at 06:31 PM.
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