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  #1  
Old 02-03-2005, 02:57 PM
mattvct
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Driveline questions

I've got a couple of questions that I haven't quite got through my head from my searches. As far as the interchangability of driveline components goes, most of the discussion has to do with swapping to manual gear boxes, which since I already have a couple of 5speed cars, is not of as great importance as my ability to easily drink coffee and make phone calls on my way to work .

As far as automatic transmission interchangeability goes, are any of the automatic transmissions from the 2.5L cars easy swaps-outs? If so, what else would I need if I were to put in the tranny from say, a 1997 Legacy GT? I know that I need to match the gear ratios and all, but would I need to keep the SVX's driveshaft, or would I be able to use one from the legacy GT?

Also, if I were to swap in the manual gearbox, would I be able to use one from a 2002-2004 WRX, and if so, would there be any problem in using one of the aluminum driveshafts available from driveshaftshop.com? It would seem to me that with the aluminum driveshaft, a lightened flywheel and the lighter weight of the manual drivetrain in one of these cars, it would serve to lower the moment of inertia in the drivetrain, freeing up substantial horsepower that is lost in the drivetrain, and since the shaft would twist much more than the steel stock one, it should also dramatically reduce the shock to the transmission, possibly helping to overcome some of the stresses imposed by the SVX's portly 3500+lb curb weight.

Sorry if any of this doesn't make sense, I'm pretty new to AWD since with my old Talon TSi I never had to deal with any of the technical aspects of such a system (I've blown up plenty of FWD trannies though )
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  #2  
Old 02-03-2005, 03:05 PM
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Not sure about the 97 Legacy auto but the 2002/2003 WRX 5MT's fit great.

The WRX 5MT is also the only other tranny that you can install in the SVX without replacing the rear differential.
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Old 02-03-2005, 04:29 PM
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Quote:
Originally posted by Earthworm
Not sure about the 97 Legacy auto but the 2002/2003 WRX 5MT's fit great.

The WRX 5MT is also the only other tranny that you can install in the SVX without replacing the rear differential.
Hi Dave, hows the temp up there?

I have been intrigued by this for a while, If the rear diff is retained at 3.5 and the WRX box is used with a 1.1:1 transfer gear reduction,with a front diff of 3.9:1. The end result would be an overall ratio of 3.5:1?

This seems to be a bit high for the clutch and box. Am I missing something? or is this the way it is.

Harvey.
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  #4  
Old 02-03-2005, 04:40 PM
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Harvey, that's correct. The USDM WRX 5MT has a 1.1:1 step down for the rear drive. Effective rear axle ratio is 3.9:1.

mattvct, I'd suggest against using a one-piece driveshaft. There's one guy here that has one with his 5MT swap, and he's had vibration problems with it. I've read about a few WRX guys who tried one-piece driveshafts, and they had vibration problems too. The idea that the aluminum driveshaft torsional flexibility will help reduce shock is fine, but the SVX rear driveline already has tons of flexibility because the rear subframe and diff carrier bushings are very flexible. The result is that the SVX is very bouncy in low gears like other older AWD Subarus.

If you go manual, use a balanced two-piece Subaru driveshaft.
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Old 02-03-2005, 04:43 PM
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Weather's great! Normal high is -11°C. We'll probably see near +4°C on saturday. This past week has been way above normal.

The final drive is 3.90, not 3.54. Output to the rear wheels is 1.1 times more than the front. 3.545 * 1.1 = 3.90.

100kph = 2300rpm or so in 5th.
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Old 02-03-2005, 05:01 PM
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Quote:
Originally posted by Earthworm
Weather's great! Normal high is -11°C. We'll probably see near +4°C on saturday. This past week has been way above normal.

The final drive is 3.90, not 3.54. Output to the rear wheels is 1.1 times more than the front. 3.545 * 1.1 = 3.90.

100kph = 2300rpm or so in 5th.
Gee you must be sweltering up there

Thanks for that. I thought the transfer gear reduction was to the front diff. I'll have to look at a digram of the box.

Harvey.
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  #7  
Old 02-03-2005, 06:51 PM
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if you use the 97 Legacy auto box you need the matching Legacy rear diff. you retain the SVX driveshaft and axles.

Do a search using 4.11 and 4.44 as the search terms and somewhere in the results you'll find a fairly good write-up and links to personal lockers.

the short version is: you disassemble the SVX and Legacy rear diff to the point of pulling out the ring gear. you put the Legacy ring on the SVX center section (to retain the SVX limited slip), grind out a couple of bumps (why you need the links to lockers) and reinstall the Legacy ring/SVX center section back in the legacy rear diff - having left the Legacy pinion untouched.
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