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5MT Swap


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I am looking to pick up a replacement 5MT transmission for my son's 1996. I was looking at the transmission page on this site ( http://legacygt.com/forums/showpost.php?p=3555574&postcount=3 ) and noticed that there is a gear ratio exception for the 96's. (Of course there is, lol) Will we notice a big difference if we put in a trans from another year with the different gear ratios?
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Just replace the matching rear diff with the one from the 5mt donor and use that donors ECU and you should be fine. Matching the final gear ratio is the most important part, the diffs have to be the same, and if you don't know what gear ratios your 96 has, it's safer just to swap both trans and diff from the donor.
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When I had to do the same, with the same possible options, I jacked up the back end, both wheels off the ground. A chalk mark on each tire and the driveshaft. Then turn the driveshaft by hand 40 revs and count how many turns at the wheels. It was real easy to tell if I had a 3.90 or 4.11 rear end. Then I got the matching (3.90) 5MT. I've got about 35k on since then. A good deal less expense and work than swapping out the rear end.
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ECU swap isn't necessary. As I learned, it's not the ECU that determines the transmission type, it's the harness that tells the ECU which transmission is installed.

 

Read this thread here: http://legacygt.com/forums/showthread.php/mt-identifier-pin-136832.html

 

As far as the matching transmission, your 96 with the auto is not hard to determine what your final drive ration is. If it's a Brighton or L AWD, it has a 4.111 FD on the transmission, which is not hard to find a 5MT to match that. Most newer Subaru 5-speeds in the early to mid-2000's were 4.11 and all you need to do is swap your speed sensors. The FWD Brighton and L model had 3.90 final drive and the fact that it's a FWD means no rear diff anyways.

 

If it's an Outback or GT, those have 4.444 FD. Only a JDM WRX 5MT, or 04-05 Forester XT 5MT, use that ratio.

 

The only exception the link says is regarding the FWD 5MT. There was no rear diff, for obvious reasons, so the FD gear ratio is naturally lower. Just because the 96 was special, just meant that Subaru still had FWD in that year. Regardless the exception does not apply to you swapping the transmissions, since I assume you have AWD and want to retain it. Refer to this chart here specifically the last two pages for USDM 5MTs. Try to stay away from a WRX transmission unless you can get the matching rear diff.

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  • 2 weeks later...

I finally spent some time under his car and, of course, we have the 96 exception transmission with 4th having a 1.088 dear ratio and the rear diff is a 3.90 ( car is a 96 Impreza awd ). Apparently this is going to limit the potential donor pool. Any idea if there are other cars that use the 5mt with the highlighted gear ratio?

 

5MT

Used in pretty much all Subarus from 1995 - 2002 including the WRX)

1st : 3.785

2nd : 1.945

3rd : 1.500

4th : 0.994

5th : 0.780 - 0.735 WRX

Final Drive : 4.11 - 3.90 WRX

1996 Exception

1st : 3.545

2nd : 2.111

3rd : 1.448

4th : 1.088

5th : 0.825 (FWD) - 0.780 (AWD) - 0.871 (Outback AWD)

Final Drive : 3.454 (FWD) - 3.900 (AWD) - 4.111 (Outback AWD)

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I finally spent some time under his car and, of course, we have the 96 exception transmission with 4th having a 1.088 dear ratio and the rear diff is a 3.90 ( car is a 96 Impreza awd ). Apparently this is going to limit the potential donor pool. Any idea if there are other cars that use the 5mt with the highlighted gear ratio?

 

3.90 gears were used in the 90-98 Legacy Brighton and L with the 5MT.

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