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96 Legacy Front or Rear Diff Change?


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15 replies to this topic

#1 lmdew

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Posted 06 September 2012 - 06:02 AM

I've got a 96 Legacy that the drive shaft went out on. It tore up the trans tail shaft pretty good. I have a good used trans but it's out of an Outback instead of the standard Legacy so the ratios are different (still have to check the #'s).

I've changed lots of rear diffs, but never the front. How's the front to change? Procedure to change the front?

Both Transmissions are out and on the ground.

#2 johnceggleston

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Posted 06 September 2012 - 08:00 AM

the details i have read about doing this were fairly involved. especially with regards to shimming the pinion shaft so it meets the ring gear correctly, tooth to tooth. smear on some blue indicator stuff, align it, try it, more blue stuff, adjust it, try it, etc. all to make sure the teeth meet correctly. so i have avoided it all together. but others have apparently done it with no problems. idk.

but, why not just swap the rear extension housing that got torn up. that is easy. was there more damage than just the tail shaft section? or do you just want to upgrade the trans in general?

#3 edrach

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Posted 06 September 2012 - 08:51 AM

Easiest thing is to change the rear diff to match the ratio of the front.

#4 Gloyale

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Posted 06 September 2012 - 10:24 AM

Just swap the tailsections.

#5 lmdew

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Posted 06 September 2012 - 07:41 PM

Trans has no fluid it it so, I thought it was better to change it out. No telling how long it was run with no fluid or how much metal got into the trans.

#6 Fairtax4me

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Posted 06 September 2012 - 08:21 PM

Front diff can't easily be changed. The pinion shaft runs through the center of the countershaft of the transmission. That has to be swapped along with the ring gear, or the whole front diff, then you have to set the pinion depth, pinion to ring gear backlash and preload on the carrier bearings. And to get to any of it you have to disassemble the whole transmission and split the case.
If you know you have a good transmission (good synchros, good input shaft bearing) and just want to swap the diff and pinion shaft it's entirely doable, but it's a lot of tedious work, and usually not worth the time. It's much easier and faster to just swap the rear diff to match ratios.

#7 grossgary

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Posted 06 September 2012 - 08:35 PM

I would swap the rear diff, i see no compelling reason at all not too.

Gloyale has done front diff swaps and mentioned quite a few details about it, i would look for his thread about it somewhere on here.

Yet he also just posted to swap the rear housing.

Probably a strong case for not much damage since the car likely didn't go far after this happened...but i totally understand the risk.

#8 lmdew

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Posted 07 September 2012 - 05:33 AM

Rear Diff it is.

Thanks for the suggestions.

#9 johnceggleston

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Posted 07 September 2012 - 06:42 AM

changing the trans and rear diff to the 4.44 FD will make the car more GT like, sportier. it will give you a little more power and a little less fuel economy. you can off set that with larger tires. the GT size, 205/55/16 or similar, will fit with out any other changes. probably not worth throwing away good tires for, but something to keep in mind for when you need tires.

it may also throw off the speedo. so keep an eye out for that. it will probably show you are driving faster than you actually are and your odo will show a mile before you actually drive a mile.

just a thought.

Edited by johnceggleston, 07 September 2012 - 06:48 AM.


#10 Fairtax4me

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Posted 07 September 2012 - 03:55 PM

it may also throw off the speedo. so keep an eye out for that. it will probably show you are driving faster than you actually are and your odo will show a mile before you actually drive a mile.

just a thought.

This is a good point, the gears in the trans for the speed sensor are different depending on what FDR you have. But if you match the tire size to the car that the transmission came out of it will/should not affect the speedometer.

#11 987687

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Posted 10 September 2012 - 06:43 AM

changing the trans and rear diff to the 4.44 FD will make the car more GT like, sportier. it will give you a little more power and a little less fuel economy. you can off set that with larger tires. the GT size, 205/55/16 or similar, will fit with out any other changes. probably not worth throwing away good tires for, but something to keep in mind for when you need tires.

it may also throw off the speedo. so keep an eye out for that. it will probably show you are driving faster than you actually are and your odo will show a mile before you actually drive a mile.

just a thought.


Assuming we're talking about manual transmissions here (it was never mentioned). The only 4.44 manual sold in the US was the forester XT.
The outback has 4.11 gears, and if his legacy is a GT it will also have 4.11 gears.

Personally I don't like the outback tranny because it has a really short 5th gear. I'd just swap the tail section to retain the longer 5th.

#12 johnceggleston

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Posted 10 September 2012 - 07:54 AM

Assuming we're talking about manual transmissions

good point, i'm an auto trans guy, and that is what i assumed.
so the info above is for auto trans.

what year did they put the 4.44 ratio in the forester manual trans? i didn't know they had done that.

Edited by johnceggleston, 10 September 2012 - 07:56 AM.


#13 987687

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Posted 10 September 2012 - 11:28 AM

good point, i'm an auto trans guy, and that is what i assumed.
so the info above is for auto trans.

what year did they put the 4.44 ratio in the forester manual trans? i didn't know they had done that.


All the forester XT (turbo) models. So I 04+

But yes, knowing what model of car, and what transmission the OP has would help considerably giving valid advise.

#14 lmdew

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Posted 10 September 2012 - 07:37 PM

Auto

#15 987687

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Posted 11 September 2012 - 05:18 AM

Well, if it's not a GT, then an outback trans will change you from 4.11 to a 4.44 front ratio.
If your car IS a GT, then an outback trans will be a direct swap in terms of gearing.

The 4.44 trans has a longer 4th gear to make up for the shorter final drive, so your overall cruising rpm will be about the same.


I have no idea about how the computer will react to gear changes. I basically know my auto works, and when it stops I'll 5speed the car... I'd think the computer wouldn't like the gear change, but someone who knows more about it will chime in there.

#16 lmdew

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Posted 01 October 2012 - 07:01 PM

Trans and Rear Diff swap went well and is running great. The speeding protection system is working well, about 10 mph under the actual speed at highway speeds.

Corrections through tires possible as far as I can tell.




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