Rear Diff ID Tag??

Hey guys, I was wondering how I can find out which rear diff I have in my legacy. I know the gear is the 3.900, but I dont know what the specific differential is. I'm looking into some different axles and was wondering how to tell. Or are they all just the same? o.O

they haven't change the rear diffs since the early 90s.

 

if your 1996 Subaru Legacy BK Wagon has a 3.9 final drive ratio then it also has a 5 speed manual trans.

 

in the late 90s they only had 3 diffs available, all and the only differences between them was the final drive ratio, 3.9, 4.11, 4.44. and they are all ''open differentials, no limited slip, and they all take axles that insert into the diff.

 

http://i249.photobucket.com/albums/gg240/johnceggleston/97reardiffratios.jpg

Thank you very much Johnegg.

Johnegg, when you did your ej22 swap did you have to change out your T2 Diff?

the diff has nothing to do with the engine, so no , i did not have to change out my diff.

 

but since i was putting a 95 ej22 into a 97 outback car, i had the 4.44 rear diff, the TP, not the T2. still go and it runs great.

John, because the final gear ratio is 4.44 on the TP diff up from the 4.111 on the T2 does your car actually run at a lower RPM in the final gear?

in the late 90s, most of the 4.44 diff ratios were matched with the larger ''outback'' tires so the difference in ratio was ''corrected'' by the difference in tire size. so i did not notice any difference in engine speed.

 

the exception to the above is the legacy GT, it has the outback gearing but tires (24.9" diameter) closer to the legacy size (24.2" diameter, outback is 26.3"). so the engine RPM is slightly higher in the GT for the same speed in the outback.

 

but it is wrong to think about engine RPM when doing a swap. if all you are swapping is the engine, not the trans or the final drive ratio, then the engine is going to have to spin the exact same number of times to go a mile. it does not matter which engine is in the car.

I noticed that the manual and the automatic have different rear diffs (4.111 and 4.444) for the 2.5 L engines. Can I swap out the diff from my broken down (Blown Head Gasket) manual 1998 Outback into my running (oil in diff is grey) 1998 Outback?

Can I swap out the diff from my broken down .... manual 1998 Outback into my running ... 1998 Outback?

??????????

I had some questions too about Diff. I have some reasons to think that either the engine, the trans or diff are not original in my GT. I do know that at 65 Mph, I am well over 3000 RPM and was wondering if every GTs are the same. At 75 I'm at about 3700 Rpm and I find it a bit high, or is it just me that is used to drive a 6 speed for the last 3 years?

 

Also, how much of an impact on the AWD system would have a rear diff with the wrong ratio for the tranny it is mounted with? Also, I've found myself a used diff, the guy says its a 4.11 LSD and thats what I need with my car (GT wagon manual 98). Is he mixed up? Considering it is maybe from something else than a Legacy, would it still fit?

if the front and rear ratios did not match the car would be bucking and binding even when driving straight. you would know it.

 

your rpm do sound high, but i'm an A/T guy so i do not know what they should be.

 

your best bet is to figure out your gas mileage. reset your trip odometer when you fill up. drive the tank and then when you fill the tank the next time, divide the miles driven by the gallons it takes to fill. then check back.

 

what size tires are you driving? 205/55/16 is stock for the 97 GT . smaller tires will increase the rpm.

 

what year is your car? 98

 

what engine? DOHC or SOHC?

 

trans? 5 speed.

 

drive shaft in place?

 

any warning lights?

 

does it shift in to 5th? it has 5 speeds right?

Ok well I got a correct pair of Diff-Trans

 

Its a 98 2.5L DOHC 5 speed. No lights. It does shift every gears smootly and I got the correct size tires.

 

So I'm presuming since if the ratios are not the same on the rear diff for an L and a GT, well their manual trannys differ, or at least the front diff in the tranny, correct?

 

I don't remember seeing a Tag on the diff when I checked, maybe it fell down with the years, or is it graved in the casing?

 

My main issue would be getting a diff that is supposedly for a GT, but having a tranny from an L Wagon, for instance.

the L 5 speed has a 3.9 ratio. that would make the rpm lower.

 

there is an ID tag on the driver side strut tower under the hood. compare the trans id# with the label on the trans bell housing near the starter. they should match.

Gargamel, it looks like you have an Oubtack.

 

5-speed OB's have a slightly taller 5th gear ratio than L or GT 5MT. That's why your RPMs are where they are while out on the highway. It's revving closer to the peak torque of thepower band. This is better for towing.

Can I take the differential in the 1998 2.5L Legacy Outback manual tran and put it in the 1998 2.5L Legacy Outback auto tran without problems? The oil in the differential of the car with the auto transmission is grey and I expect problems with it in the future. (The car with the manual transmission has a blown head gasket and will be sold or junked)

Can I take the differential in the 1998 2.5L Legacy Outback manual tran and put it in the 1998 2.5L Legacy Outback auto tran without problems?

.

NO

 

the 98 2.5L 5 spd has a 4.11 FD ratio.

the 98 2.5L auto has a 4.44 FD ratio.

 

you need the rear diff from a 96 - 99 2.5L car with an AUTO trans.

Gargamel, it looks like you have an Oubtack.

 

5-speed OB's have a slightly taller 5th gear ratio than L or GT 5MT. That's why your RPMs are where they are while out on the highway. It's revving closer to the peak torque of thepower band. This is better for towing.

 

Hmmm... thats a possibility. There's a lot more Outbacks over here than GTs, if the engine and tranny failed and were replaced, they could have pick them from an OB. I guess I'll only know when I check the tag on the tranny.

 

What are they for the GT and the Outback?

 

To my understanding, OBs and GTs share the same Diff ?

if the front and rear ratios did not match the car would be bucking and binding even when driving straight. you would know it.

 

 

no true. i had a 4.11 mated with a 3.9 diff and it drove fine. but parking lots were another story. the car would stop rolling while turning. and it was not noticeable untill about 100-200 miles after the center diff went to hell.

Ok, John. I accept that. But how does one tell which diff is in there? Where are the markings that say "T2" or "TP"? On top? On the side? Back? Bottom? I will need that info when I go to the junk-yard.

they used to put id tags on the rear diffs in the early 90s, but i don't remember ever seeing one.

 

i identify the ratio by the car it is coming out of.

 

if i understand correctly you are look for a rear diff for your 98 outback auto trans, right????

 

you can use the rear diff from any 2.5L auto trans car, 96 - 99, outback, GT, forester, or LSi. outbacks are going to be most common.

 

to repeat:

 

ALL rear diffs, 96 - 99 from 2.5L auto trans cars are the 4.44 ratio that matches your 98 outback auto trans. (not sure about the high end imprezas like WRX, RS etc.)

 

 

 

the 4.44 was also used in the 00 - 04 auto trans outbacks, and GTs; (and i think foresters but i would need to double check.)

the 3.90 was used in the 95 - 99 and the 00-02 (at least) auto trans leagcy L, brighton, and the low end imprezas.

 

so when you see an outback that looks like yours, look to see if it is auto trans. if yes, the diff will work.

 

but i would not swap it out as a preventative measure. they are very very hardy and do not fail very often. replace the gear oil and see how it does. if you are really concerned you could use some special purple stuff or something, but i doubt you need to. maybe it got some water in it. did you drive it through a creek???

OK John, here are the symptoms. A low frequency rumble somewhere from mid to rear that is most pronounced at around 45mph. It seems to be slightly detectable at all speeds, though. I've suspected the center drive shaft bearing but the grey oil in the rear diff sent me down this path.

the most common cause of rear noise is wheel bearings, then drive shaft, then rear diffs.

 

replace the gear oil and then try a track down the noise. have someone drive while you ride in the back seat at listen to each side.

So after further investigation, it seems the rear diff I got is a 4.11 LSD from a 2002-2005 automatic WRX, my guess is that I just got a sweet upgrade from my non LSD stock one, it should fit as its the same ratio, right?

it should fit as its the same ratio, right?

 

what car? year?