Subaru Outback differential rebuild

[Lverano]

If I pull the transmission on my 2003 automatic L.L. Bean Subaru outback H6 I'm going to try to rebuild the differential using parts from the junkyard, and while I'm in the junkyard, give myself a course on how to take the differential apart. I turn to the forum to ask what tips if any can anyone give me on rebuilding this particular diff?

[idosubaru]

backlash and bearing preload make this not for the faint of heart - very few people do it. 

 

Did you drive this car with a failing diff for awhile? 

 

the one I disassembled had some damage in the rear extension housing - shims were busticated and had significant wear.  

i'm assuming the front diff may have caused that rear extension case wear through too much shaft play?  if that's possible (i'm just assuming that) and yours has similar wear - does that wear leave any play that could damage the new front diff?

- you might want to inspect yours or even migrate the entire donor trans rear extension housing assembly onto/into your trans.

 

that uncertainty aside (i'm not sure), here's what the process looks like:

 

get everything from the donor transmission front diff into your existing transmission.  

You want to gut your transmission diff case and install everything exactly the same way it was in the donor transmission.

get all the shims, side bearing cups with seals, count the number of turns when removing the bearing side seals and reinstall them exactly the same way so you're retaining the same clearances that were in the donor trans (theoretically/hopefully anyway).

 

get an exploded view of the front diff and the FSM pages correlating to the front differential so you can see all the bits and removal/build process.

 

technically you should be resetting bearing preload and backlash from scratch since it's a different case, but one guy on this forum did it before in his forester (you can search and find his thread).  i talked to him and was about to try it myself but i stumbled on $75 transmission i was going to use the front diff for but it ended up only needing some wires repaired and pan replaced so i used that as-is and never had to dig into the front diff. 

[Lverano]

I did read his thread, it inspired this thread! I drive mine regularly. By the time the transmission fails, I might Just have a good JDM on hand...

 

Not any YouTube videos on the tear down of this transmission. Just starting to learn about preload and backlash, seems complicated for sure. An amazing YouTube video would be to see someone attempt this ..

Like the forester guy said, once you lay the two trans side by side and see it for what it is, seems as though somewhat simple, and like you said, just put all the pieces exactly how you found them in the donor..

Edited August 25, 2016 by Lverano

[idosubaru]

Gloyale has commented some on front diffs and backlash over the years:

 

http://www.ultimatesubaru.org/forum/topic/145014-99obs-mt-diff-side-retainer-and-seals/

 

http://www.ultimatesubaru.org/forum/topic/87305-easy-transmission-front-seal-replacement/

 

i feel like he had an automatic he replaced bearings in as well too, but i can't find that thread.

Edited August 26, 2016 by grossgary

[Fairtax4me]

It's not that complicated, just time consuming and tedious to get everything set correctly. It also requires a few tools that the average DIYer doesn't have.

 

Seems to me the biggest problem with the front diffs on these is the front pinion bearing. Problem is when that goes out it causes the pinion and ring gears to chew each other up. Clearance between hypoid gears can't be "good enough" it has to be pretty exact or they'll grenade in a very short time. So the challenge when doing a rebuild is to get the clearance set perfectly.