Axle Ratio Question, unable to find the answer I need

[Ionlyhave3suubs]

I recently picked up a 97 Legacy GT sedan to use as my work car. I purchased the car knowing the transmission was in bad shape and would need a rebuild or replacement. I removed the transmission this week and had plans to swap in a 98 Outback transmission. I inspected the ring and pinion on both and determined the transmission in the GT which the PO advised was a low mileage JDM swap had a 4.111 ratio. The Outback transmission had the correct 4.444 ratio that should be in all of the 4eat 97-98 2.5 powered cars. I have searched the forums and not been able to find decoding information for rear axle ratios. I was only able to find a small sticker on the back of the rear differential housing with "T2" on it. does this indicate the gear ratio? If so, what is the ratio? My theory is the PO swapped out the original transmission with a transmission with the wrong ratio and damaged the transmission due to the incorrect ratio. The engine and transmission that were in the GT when I bought it were JDM swap according to the PO. He did not have the paperwork on the JDM engine or transmission. Both looked really clean, however the transmission is noisy and the PO said it slips at highway speed. The fluid smells burnt.

 

To reiterate, I need to know how to tell the rear differential ratio so I match up the front differential correctly when I put a transmission back in. I know it should be 4.444, but since other things have been swapped and there is no paperwork for those items, I don't feel comfortable assuming it is still the original rear.

 

I am starting to have suspicions this car may have been a 5MT car to start with. I'm guessing that information would be in the VIN somewhere. Can someone tell me where that is in the VIN?

Edited April 26, 2017 by Ionlyhave3suubs

[idosubaru]

Turn a rear wheel and count wheel rotations verses rotations of the front diff flange. That will give your ratio.

 

Google Subaru VIN decoder to decipher the VIN.

 

that would be a beastly wiring job, what makes you think it was swapped?

Edited April 26, 2017 by grossgary

[Fairtax4me]

I don't remember the VIN exactly but if you look on the drivers strut tower there should be a metal tag with the original engine and trans ID numbers.

 

If it starts with TZ it was an automatic

TY means it was manual. Likely it was an automatic since a manual to auto swap is 10x more work than going the other way. Harness HAS to be swapped to go from manual to auto since the AT cars need the TCU and harness and MT cars don't need any of that.

 

I don't remember any outside identifiers for telling the FDR on the rear diffs. Pretty sure the only good ways to determine that are to count turns or open it up and count teeth.

 

Gary makes a good point though. There should be a VIN stamp on the trans somewhere and decoding that will at least tell you what year and model the trans came from which may help determine the FDR.

Edited April 26, 2017 by Fairtax4me

[Subaru Scott]

I'm almost certain the "T2" indicates 4.11... almost.

[wtdash]

See the attached for the VIN tag.

 

As noted the TZxxx is 4EAT; TYxxxx is 5MT.

 

Some of the online VIN decoders aren't 100% accurate; the VIN tag won't lie.

Edited April 26, 2017 by wtdash

[Ionlyhave3suubs]

Gary, I just tried the wheel turning method and came up with 4.11:1. I suspected the 5mt to 4eat swap due to doing the wheel turn test, but not being sure I was doing it right and coming up with 4.11 ,and on the firewall in the place where a clutch master cylinder would be, there is a piece of aluminum tape over the hole. According to the plate on the strut tower, however it was equipped with a 4eat from the factory. I am guessing the rear diff was swapped out when the transmission was because the front diff is definitely 4.11. I was under the impression all 2.5 4eat ratios should be 4.44

 

Fairtax, I know the front diff ratios already. I have the front diffs removed from the transmission cases and have counted the teeth. I was trying to figure out the rear ratios so I could use which ever one I needed to to match the rear, since I have one of each of the front ratios.

[Ionlyhave3suubs]

Thanks to all. I will be going with the 4.11 front diff to match the rear, even though it is probably not the original axle ratio that came in the car.

[idosubaru]

nice work.  you're going to swap front diffs?  backlash and bearing preload setting and all?

 

I've swapped 3.9 or 4.11's into originally equipped 4.44 automatics before, it happens ocassionally, usually driven by transmission swapping/repairing. 

why did you choose 4.11 in this case?

[Ionlyhave3suubs]

Gary, I bought the car with the 4.11 trans and rear already installed. The 4.11 trans is no longer a viable trans due to obvious overheat. The fluid has the burnt smell. I have a friend who runs an independent transmission shop and he is helping me out with the transmission rebuild. Due to the apparent transmission damage, I am opting to rebuild the Outback transmission even though the car it came out of has a bit over 200k but on teardown the friction materials and steels have little to no visible wear. It was likely recently rebuilt or a low mileage swap. Due to all of these factors, my transmission guy and I determined the best option would be to rebuild the Outback transmission, swap out the front diff and bellhousing from the 4.11 trans that was in the car when I got it, and re-install. I am hopeful the  smaller diameter GT wheel/tire combination will even things out with the slightly higher gear ratio. It would be a bit less work than pulling the diff from the Outback, and swapping it into the GT, plus the added work of removing the gears from the damaged Outback bellhousing and putting it in the undamaged bellhousing that came in the GT when I bought it.

 

Additionally, I realize now I left out a fact in my original post that when removing the Outback trans from the donor car, It fell off of my cheap jack and the passenger side lower corner of the bellhousing hit the concrete floor in my garage, cracking the bellhousing. That was the whole reason I began opening up the transmissions in the first place.

 

I guess the best explanation is the 4.11 kinda chose me based on the whole circumstance.