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Need Instructions for Front Diff Removal, 4EAT


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10 replies to this topic

#1 Camaro98

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Posted 04 May 2011 - 08:58 AM

Hi guys,

I've been looking all over the internet for instructions on how to remove the front differential from the transmission on my 4EAT automatic transmission, but all I can find are instructions for manual transmission cars. Does anyone here know how to properly remove/reinstall a front differential on a pase II 4EAT?

What's going on is: I have a 2001 Forester (auto) that had a buzzing front diff. The transmission shop diagnosed it as a bad pinion bearing. Rather than pay the shop up to $1100 to rebuild the front diff, I decided to get a whole used transmission. I installed it, drove it (problem-free) for about 30 miles, and then the "new" transmission went bad (acting like torque converter or front pump). Lots of symptoms and a code P0741 (Torque converter something-or-other stuck closed). Toast. So, the replacement tranny has a good front diff, but a bad auto transmission.

I want to take the good front differential off of the bad transmission, and swap it with the bad front diff on the original (good) transmission. I know this has been done, but can't find instructions and don't want to botch it by going in blind. Any instructions and/or exploded view diagrams of this procedure for a 4EAT would be a really big help.:)

#2 grossgary

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Posted 04 May 2011 - 09:20 AM

the key is setting the backlash on the front diff. normally you could entertain the idea of just retaining the backlash but since you're swapping parts you may be starting from scratch?

maybe you could search for "setting backlash" or "backlash" and see what you come up with.

or read through a Factory Service manual portion detailing that process.

otherwise it's mostly just unbolting the front diff from the trans, that part isn't all that difficult, just a bunch of bolts and the retaining rings.

i gave someone a transmission to do this job and the "new" diff only lasted a couple months before it failed again.

#3 grossgary

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Posted 04 May 2011 - 09:25 AM

Gloyale is good, here's one thread he discusses it some including the dial through the drain plug hole to set the backlash:
http://www.ultimates...backlash&page=3

#4 Camaro98

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Posted 04 May 2011 - 12:52 PM

Thanks for the info, guys. The thread was a good insight into what I'm considering with this project.

How do you remove the pinion shaft, though? I know that you remove the front diff case, and then the tailshaft. What do you do after that?

#5 johnceggleston

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Posted 04 May 2011 - 01:23 PM

i don't think the pinion has to come out. it is mounted in the trans, thru the oil pump and the front diff mates to it.

i had a how to on this but i can't find it. i'll keep looking and let you know if i do. as i remember the file has to be attached to an email.

any one seen a link or file at josh's http://www.main.expe...u_manual_scans/

#6 Camaro98

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Posted 05 May 2011 - 07:10 AM

Well, I got some practice in last night. I have another phase II transmission that came out of an H6 Legacy (have been trying to sell it, but no takers); and since it has been uselessly cluttering up my garage, I decided that it would make a good guinea pig. Taking it apart was actually a lot easier than I thought it was going to be.

The front diff case was straight forward, but had to be coaxed with a mini sledge and a pry bar to separate the cases after the bolts were removed. Removing the pinion was easy as well....4 bolts at the front flange, and the large staked nut at the rear end of the shaft. The pinion bearing came out on the pinion shaft, apparently preloaded and staked in position. All in all, I feel confident about doing the work on the good transmission after seeing the guts of this one.

Now for more questions:

1. When installing the donor pinion into the transmission that I will be using, do I use the pinion flange shim(s) from the donor transmission, the accepting transmission, or does it not matter because they're all the same? I want to make sure that the pinion depth is correct.

2. Is there a torque spec for the large nut at the rear of the pinion shaft?

3. There is a rigid gasket for the tailshaft housing. Is this gasket safe to re-use? If so, can it be reinstalled without any RTV as it originally was?

4. I didn't see a gasket on the front diff housing. Does anyone know what Subaru originally used to seal the housing to the transmission case?


Thanks again, guys!

#7 johnceggleston

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Posted 05 May 2011 - 07:42 AM

Removing the pinion was easy as well....

1. When installing the donor pinion into the transmission that I will be using, do I use the pinion flange shim(s) from the donor transmission, the accepting transmission, or does it not matter because they're all the same? I want to make sure that the pinion depth is correct.

3. There is a rigid gasket for the tailshaft housing. Is this gasket safe to re-use? If so, can it be reinstalled without any RTV as it originally was?

4. I didn't see a gasket on the front diff housing. Does anyone know what Subaru originally used to seal the housing to the transmission case?

Thanks again, guys!


tell me again why you are replacing the pinion shaft? are you changing the final drive ratio? i doubt they are a matched set. and although they may have ''worn'' to br matched the chances of you getting them exactly the same as they were is pretty slim. for that matter, if they have worn to a matched condition you probably don't want to use it. just my opinion.

the trans shop that swapped my rear extension housing used a silicone based gasket material. i assume RTV ultra gray would do. same for the front diff case. of course, don't use too mush , you don't want it to goop into the case and cause problems. (the diff would be less of a concern than the rear housing since the diff doesn't have a pump.)

#8 Camaro98

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Posted 05 May 2011 - 08:33 AM

I'm changing the front diff and pinion shaft because the front diff in the original transmission is shot. When it was in the car, I had a lot of high-pitched whining and buzzing going on; it was diagnosed by a transmission shop as a bad pinion bearing in the front diff. I would just get the bearings changed, but I have been warned by a handful of mechanics that the gears are likely damaged after driving the car like that for the last 7 months. And I do not want to pay $325 for a new ring and pinion set if that can be avoided.

Maybe I'll get lucky and find out that the problem is just a carrier bearing when it's all taken apart, and the gears will be fine. That's probably hopelessly optimistic, but there's only one way to find out for sure...

...I still need to know about the shims and pinion nut torque, though...;)

Edited by Camaro98, 05 May 2011 - 10:20 AM.


#9 seanrob

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Posted 19 July 2011 - 10:45 PM

Do you still have the front housing from that trans? I had my H6 trans bell housing crack and break on me, so I'm looking for another one before I use an older housing.



Well, I got some practice in last night. I have another phase II transmission that came out of an H6 Legacy (have been trying to sell it, but no takers); and since it has been uselessly cluttering up my garage, I decided that it would make a good guinea pig. Taking it apart was actually a lot easier than I thought it was going to be.

The front diff case was straight forward, but had to be coaxed with a mini sledge and a pry bar to separate the cases after the bolts were removed. Removing the pinion was easy as well....4 bolts at the front flange, and the large staked nut at the rear end of the shaft. The pinion bearing came out on the pinion shaft, apparently preloaded and staked in position. All in all, I feel confident about doing the work on the good transmission after seeing the guts of this one.

Now for more questions:

1. When installing the donor pinion into the transmission that I will be using, do I use the pinion flange shim(s) from the donor transmission, the accepting transmission, or does it not matter because they're all the same? I want to make sure that the pinion depth is correct.

2. Is there a torque spec for the large nut at the rear of the pinion shaft?

3. There is a rigid gasket for the tailshaft housing. Is this gasket safe to re-use? If so, can it be reinstalled without any RTV as it originally was?

4. I didn't see a gasket on the front diff housing. Does anyone know what Subaru originally used to seal the housing to the transmission case?


Thanks again, guys!



#10 bheinen74

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Posted 20 July 2011 - 12:09 AM

sounds like the replacement trans was fine, you drove it for 30 miles. Did you read up on how to "seat the torque converter" before you installed the replacement. It does sound like you fubarred the trans pump not seating the TC right, based on what i read. I would reckon if you didnt search that proper issue, and you didnt seat it correct, you will be going thru this yet a 3rd time.

be careful, take you time, get it right.

#11 Camaro98

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Posted 20 July 2011 - 04:23 PM

Hi, bheinen74. I didn't look up the instructions on seating the converter beforehand, no. I had done transmission jobs on a couple of Camaro's in the past, and felt familiar with seating converters from those jobs (although the Subaru converter does sometimes give a little more hassle on the way in). The guy helping me was a used-Subaru dealer/mechanic from my church who had done a number of these jobs before. Looking up the procedure afterward, the guy who helped me did follow the procedure....not that it helped in my particular case, as is explained below.

Anyway, I didn't realize that I never posted an update to follow up in this thread. The car has been running and driving fine since the last week or so of May. I used the front differential& pinion from the toasted junkyard transmission with the torque converter and main transmission section from the original transmission. The wife has put about 1300 miles on the car since then, with no problems.

The gears in the original front diff were undamaged, but the forward pinion shaft bearings were definitely bad. While there wasn't any noticeable play, the bearings felt very pitted when spun by hand....much like often happens with the rear wheel bearings on these things.

While taking the junkyard tranny apart, we found out that the large splined shaft from the torque converter had fractured where it goes into the front pump. There were metal particles and shavings throughout the hydraulics, which meant having to flush the cooler and lines on the car. My helper that day was the one who seated the converter. He works on these cars as his living, and he was hesitant to let me use the transmission in the first place when we pulled the converter off to replace the seal. When we pulled the converter, a little bit of water trickled out from the direction of the front pump. The splined shaft had a few patches of surface rust on it, too. We cleaned the rust and he seated the converter when I insisted that I wanted to try the tranny out, and it went on hard. Not "I can't get it to seat properly" hard, but "it doesn't even want to spin very easily" kind of hard. There was something wrong in that front pump area to begin with, and we really knew better than to use that transmission. On that one, I took a gamble and lost. Because of the resistance we encountered, yes it could be possible that the resistance kept my assistant from being able to properly "feel" that the torque converter was seating properly, and that he may have forced it in far enough...but not properly. Again, just spinning the converter each direction while he tried to seat it was a dead giveaway that something really wasn't right to begin with.

Seating the original torque converter on the original transmission was a snap. Spun it left, then right, then clunk...it went right into place. It spun normally, too. Swapping the front diff, while needing to be very careful, is not a hard job once the transmissions are on the floor or a bench; and it can be done with a conventional arsenal of mechanic's tools.

Seanrob, yes I do still have all of the parts to the H6 transmission, including the front differential/bell housing.




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