KZJonny Posted April 29 Share Posted April 29 Yeah, but confirm first. It's unlikely the trans and diff are not the same ratio. (Tho possible) If the rear diff was swapped to match the Forester trans, then you're golden. I'm with Infosecdad here. I don't think the trans would have survived even months of being attached to a different ratio differential, should have burned it up pretty fast. If not, then you can just get the diff from the WRX as well and match the two. Probably still a better idea than keeping that NA transmission. I think it is unlikely to live a long happy life behind a turbo engine with the extra torque. And if would save you from doing the job twice. That would mean you'd need to know the spline count and size, etc... from a WRX diff, but they probably use an R160 as well, so very possible they are the same. Biggest differences are make or female on the axles, but I would think since Subaru used most of the same style parts for a lot of years, they would likely be compatible. It'll help a lot if you put the year and some details about your car in your sig or online profile. Save those who are trying to help from having to go looking to figure out what it is you are working on etc... (Ie: MY05/06 are the only GT that have a 4.11 final drive 5MT, I am pretty sure... it went to 3.9 after that.) Link to comment Share on other sites More sharing options...
Infosecdad Posted April 29 Share Posted April 29 Yes, for the Legacy GT 05-06 is 4.111 and 07-09 is 3.900 for the rear diff. You can check on cars101.com or https://rallispec.com/downloads/Transmission ID Chart_Public.pdf If the WRX diff is different for the axles, get a 05-06 LGT rear diff, it's still 4.111 and matches your axles. Link to comment Share on other sites More sharing options...
KZJonny Posted April 29 Share Posted April 29 Not to muddy the water too much, but make sure it's LGT as well. OBXT is different ratio. Pretty sure the autos are different than manual ratios as well, if the donor source is uncertain. 1 Link to comment Share on other sites More sharing options...
nebula72 Posted May 2 Author Share Posted May 2 (edited) Looks like after spinning that rear tire 20 times, the shaft turned just over 41 times so according to the formula, the grear ratio is 4.1 which matches the NA forester transmission. Ill shop around for a wrx 6 speed. If I dont find a killer deal I might just run this NA trans until it breaks as I picked up the correct fork and all fits now. Thanks so much on helping me solve this mystery. Edited May 2 by nebula72 1 1 Link to comment Share on other sites More sharing options...
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