Front differential noise and backlash

[aKro]

As you can see in my intro, we are working on giving a new life to a long forgotten gen 2 H6.

Here’s the problem with the front diff :
We do not know the maintenance history of the drivetrain.
Since the beginning, we notice some oily aluminum filings near the RH side of the front diff, the retainer seems a bit loose.
Not knowing what we were doing, we took a bad decision : we tighten the retainer 3 notches.

This appends 10K miles ago, during these 10K everything went perfectly right, only oddity, a little noise, when hot, accelerating in uphill curves.
Noise is low and similar to shaft ones (clac clac)

Last week, when we put it back on the pit for changing oil, we discovered, as you can see on the attached picture, that the leaking problem seems worst and that some oil exited thru the gauge.

We now know that rotating the retainers sets the backlash and the preload/tooth contact.
Do you think that we already ruined the front diff ?
Is there a method to adjust the backlash without Subaru special tools ?
Is following the procedure (FSM AT-78), changing seals, oil and even retainer if necessary could be enough ?

We will flush the oil, and I’ll keep you posted

Thank you for your time and precious opinions

[GeneralDisorder]

Probably will eat the front differential. Best to replace the transmission. 

GD

[aKro]

Thank you for your reply.

I was afraid that someone with Subaru knowledge reply that. Replacing transmission is a lot of work, and we are not even sure that the other one is totally compatible (it's a 2001 and we saw some differences on VDC models between 2001 and 2002).

Did anyone succesfully set the backlash, in place and without Subaru special tools or is it just impossible ?

Do you think that it's possible to judge how bad is the diff now by looking thru the flush plug ?

Thanks again we are feeling less lonely

[idosubaru]

car-part.com or jdm transmission 

I doubt you have any options. No one knows enough to tell you how to do this and probably no one has done it any statistically meaningful number of times in potential failure situations.  You’ll simply get no replies and any reply you get won’t carry much weight  

Ive had one bad diff I nursed and looked into backlash and preload options and got nowhere. Trans ended up driving poorly and locking up after 10,000 miles or so. 
 

[GeneralDisorder]

Once it starts down the path of eating the gears - no amount of setting the lash is going to fix it. You would have to get a new ring and pinion and that's not economically viable. Replace the transmission with a used one. 

GD

[el_freddo]

This is similar to what used to happen to the EA82 autos - the seal between the diff and auto trans would let go, auto fluid and diff oil would mix, pinion bearing would give out and end up allowing the pinion gear and shaft to move forward to munch the centre of the diff. This usually resulted in a front wheel lock up and a destroyed front diff. 

As others have said, a replacement transmission is the way to go. The hardest part is unbolting the torque converter from the flex plate I reckon. Keep the torque converter in place when removing the old and fitting the replacement. Or get a shop to do it for you. 

The sun dials are only going to be a band aid measure at best I reckon. 

Cheers 

Bennie

[1 Lucky Texan]

16 hours ago, idosubaru said:

car-part.com or jdm transmission 

I doubt you have any options. No one knows enough to tell you how to do this and probably no one has done it any statistically meaningful number of times in potential failure situations.  You’ll simply get no replies and any reply you get won’t carry much weight  

Ive had one bad diff I nursed and looked into backlash and preload options and got nowhere. Trans ended up driving poorly and locking up after 10,000 miles or so. 
 

 

France, might be tricky.

 

[1 Lucky Texan]

Akro, if you decide to replace the trans, do a search of the forums and internet about seating or retaining the torque converter. If it slides forward, it can cause issues when bolting in the trans. Possible cracked hydraulic pump.

[aKro]

Thanks again guys.
Today we flushed the diff after one last test with the mechanic (my brother) behind the wheel.
For him, the car is working very well, no shaking at all and the noise is very low and only when turning left, he’s not sure that it came from the diff, maybe shaft.
He has experience with bad transmission but not on Subarus.
Before flushing, we took temperature of the diff : 150 °F on each side (after about 12 aggressive miles)
One shaft was hotter than the other and was missing grease, we’ll replace it (maybe it’s the noise).
We also think that the dipstick o-ring is bad, may the reason why we have oil exiting from the top.

The oil level was good, the oil is very nice (no metal or ATF).
As you can see on pictures, residue on the plug is very limited.

For my brother, it’s premature to replace the entire trans now, he would like to change seals and the retainer on the RH side, and put it back as it was at the beginning (loosen 3 notches).
He think that what is leaking is aluminium that come from the retainer or the bloc, maybe dead retainer o-ring and vibrations ?
Our problem is how to change the retainer without loosing the backlash setting, we will count the turns extra carefully, any other method ?
Do you think it could be better doing the FSM AT-78 procedure ? Any advice ? 

Maybe, as you said, all this will end up changing the trans, but we will try not to.
Lucky Texan, thank you for your advice about the torque converter, we know that’s an issue, my brother want to remove it with the trans, I hope we can avoid all this…

[idosubaru]

Install a used or new Subaru axle with fresh grease and boot.
 

Maybe that’ll take care of the issues. 

Mark retainer location to trans case, count turns and reinstall to same position. 

[1 Lucky Texan]

plug looks good to me - minimal residue.

 

I realize it is xtra work, but axles are L-R exchangeable, then, if the turning noise moves with the axle, that should exonerate the diff right?

Edited June 6, 2022 by 1 Lucky Texan

[nvu]

On 6/5/2022 at 11:16 AM, aKro said:

Our problem is how to change the retainer without loosing the backlash setting, we will count the turns extra carefully, any other method ?
Do you think it could be better doing the FSM AT-78 procedure ? Any advice ? 

Mark it with a paint pen.  Or use a center punch.   Then count the number of turns when taking it out.  Do one side at a time.

On 6/5/2022 at 11:16 AM, aKro said:

He think that what is leaking is aluminium that come from the retainer or the bloc, maybe dead retainer o-ring and vibrations ?

If it's really aluminium, it sounds like the bearings are so worn they're grinding away the case.  

[89Ru]

Agree with what has been posted thus far. 

I realize you are past this point. However it cannot be overemphasized to avoid altering the backlash from factory setting.  Messing with it opens a can of worms. However if you are reading this you may have (like me) blundered into rotating something you now regret. At some point you may need to go down this road if you purchase another transmission and someone has bungled it prior to your ownership. Going through this procedure will likely not fix your current situation as the damage has been done. I expect you have returned the ring to its former position and hope for the best. 

Proceed with caution! I did this once, years ago, and hope to not have to repeat it. As of this post the car is still on the road with that same transmission after 25000 miles. 

This procedure is expected to be done with the transmission completely out of the car and mounted on an engine stand for ease of maneuvering. In my opinion it is impossible to perform on car in its entirety. 

I had a failed 1996 Impreza Outback sport manual transmission (was popping out of 4th gear and 2nd gear was a mess) so I purchased a used transmission. Part of my prep getting ready for the swap was changing axle seals. I marked L side but did not realize the difficulty in setting the backlash and preload so I did not bother to mark the R side and lost its factory setting.  This is how I managed to recover from my initial mistake. 

Setting front differential backlash/preload. basic idea is to return bearing preload to existing value.
Do one side at a time. Do NOT remove both retainers at the same time. You may make a tool out of pvc pipe using a cutting wheel to carve out notches to fit into teeth of seal retainer for ease of rotation without breaking a tooth.  Brush mineral spirits all around prior to removal of retainer.  

steps to set backlash and preload.  basically following the FSM procedure plus other mods.
mount transmission on engine stand
Mark L seal retainer position with a punch or marking pen prior to removal
remove L shaft seal retainer.  Press out old seal and remove o-ring
reinstall L seal retainer partially, w/o o-ring
rotate transmission so L axle shaft side is down
Mark R seal retainer position
remove R seal retainer.  remove seal and o-ring
place 10 lb. weight on bearing ring using tail cone 
You will need to turn the transmission input shaft. I used a clutch spline mating ring and a c-clamp
 
Turn L seal retainer in with PVC mating tool while turning input shaft to get the point where there is binding and back off 1/4 tooth.  This point takes a while to get to feel the binding.  Install tooth lock.  Flipping tooth lock around will allow 1/2 tooth adjustments.   I think the retainer was about 1/2 tooth from the original location.  
remove R bearing weight.  
Turn in R seal retainer w/o o-ring while turning input shaft until it begins to bind.  It was about 4 teeth between slight binding and almost not being able to turn the seal retainer.  
install R seal retainer tooth lock.  
this is the zero point.  
If I remember right the procedure calls for loosening the L retainer by 1.5 teeth to set the backlash and tightening the R retainer by the same, plus 1 full tooth to set the bearing preload.  
Use a precision dial indicator to measure backlash through the oil drain plug access point
Mark the pinion gear in four places on both sides with yellow gear marking paint.  Rotate the input shaft until a clear pattern is seen on all the pinion gear teeth.