Rear differential nightmare

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entirelyturbo
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Rear differential nightmare

Post by entirelyturbo »

The 4.111 LSD rear differential in my B4 has been adorned with more pampering and TLC than any R160 differential deserves.

Last year, I had to replace the pumpkin cover that I cracked, and around 6 months ago, the left side seal started leaking.

So, I decided I was going to remove the entire differential from the car and reseal the entire goddamn thing. Every seal and gasket that comes in contact with oil was replaced, including the driveshaft seal, which wasn't even leaking.

Once the new side seals and retainer O-rings were installed, I was VERY, VERY careful to follow the torque specs of the retainer bolts exactly (which are something like 7.6 ft-lbs). Having never messed with differentials before, I was concerned that I was going to overload the bearings and burn them up if I tightened the bolts too much.

Well, apparently, that's not enough torque, and the O-rings on the retainers started sweating.

Image

A few months later, I drove 2 hours to a Subaru dealer in Jacksonville to see a senior master Subaru tech about this fiasco, and I took complete new retainers with seals already in them and new O-rings (and new retainer bolts for the hell of it) and had him install them. He told me I did a very good job other than undertorquing the bolts. He said "yeah, don't go by the FSM on that stuff." Great. Thanks Subaru.

I figured the problem was taken care of, since it was performed by the most qualified Subaru technician there is.

But I got underneath the car last night, just to double-check:

Image

I am beyond pissed off. Sure, it's a minor leak, and people have driven Subarus for years with such an issue without any catastrophic failures. But with the amount of time, money, blood, sweat, and tears I've invested to try to fix it, I feel I have the right to expect the leak to come to a complete 100% stop.

I have a friend who retired from Universal Studios as an engineer on some of the rollercoasters there, especially the running gear, and we had a good talk about bearings and seals and so forth. He told me that since the bearings were tapered and side-loaded rather than at a direct 90º angle, overloading them would be very unlikely, so he said tighten the bolts as much as I need to, within reason of course.

He also suggested that if I do this again, that I soak the new O-rings in brake fluid overnight, which will cause them to swell up slightly, which may help them seal more effectively.

I plan on doing this once and for all within the next couple months or so, and I'll post back with the results.
2000 Subaru Legacy B4 RSK

"Der Wahnsinn ist nur eine schmale Brücke/die Ufer sind Vernunft und Trieb"

*Formerly DerFahrer*

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PhyrraM
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Re: Rear differential nightmare

Post by PhyrraM »

The advice about over tightening related to bearing load is not accurate. Once the retainer bottoms to the housing, the bearings are at the final preload, regardless of further tightening or not. The bearing preload is actually adjusted by the amount of shims, which positions the retainer slightly closer to or further away from the case.

A thin amount of RTV sealant on the flange part of the retainer would act as a proper backup to the O-ring.
'93 Winestone SS Auto, '91 Pearl White SS.
'93 Pure White SS EJ20G slanty intercooled, SIDESWIPED! In stasis.
'94 FWD and '95 AWD Laguna Blue SVXs.
2017 Pure Red BRZ Limited w/Performance pack
Legacy777
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Re: Rear differential nightmare

Post by Legacy777 »

I was going to make the same comments PhyrraM did. Tightening the bolts any more isn't going to help. I suspect the tolerances where the o-ring seal are slightly larger and as such the o-ring isn't sealing as it should. I don't know if I'd stick the o-ring in brake fluid to make it swell. It may reduce back to it's old size or could fail sooner.

As PhyrraM mentioned, a small amount of RTV sealant should help.
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
entirelyturbo
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Re: Rear differential nightmare

Post by entirelyturbo »

Thanks for the advice, guys.

The grey, curing RTV? Or the blue RTV that doesn't cure and stays tacky?

I think you all will have a better answer to this as well...

I know this is probably being unreasonable, but I want to get new bearing races to press into the new retainers beforehand, to save me the process of extracting the old races out of the old retainers, and possibly scratching/damaging them.

I'm not an expert on bearing manufacturing processes... does the fact that I'm using a different race than what the bearing was originally manufactured with mean that I would be changing the preload? And then I would have to measure backlash and all that and order new replacement spacers by the correct thickness?

Or could I just get away with the old spacers?

I really, really don't want to have to screw around with this differential again except for oil changes. So I need to be sure I'm doing it 100% right this time.
2000 Subaru Legacy B4 RSK

"Der Wahnsinn ist nur eine schmale Brücke/die Ufer sind Vernunft und Trieb"

*Formerly DerFahrer*

@entirelyturbo on social media, including Facebook, Instagram, Twitter, and TikTok
PhyrraM
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Posts: 1980
Joined: Thu Aug 11, 2005 4:34 pm
Location: Lake Elsinore, CA

Re: Rear differential nightmare

Post by PhyrraM »

Yes, any deviation from the parts on the diff as built from Subaru will mean a new setup.

I am going to assume that the master tech did a proper set up with your new retainers.

I think your overthinking this at this time. Past failures and frustrations can make you do that.

1. Remove the retainer. Only remove one side at a time as removing both sides will allow the differential inside to drop and may hinder installation.
2. Clean, replace seals and O-ring. Only change the bearing cup if it shows excessive wear. Lots of info and pics to be googled if you need advice.
3. Clean the surface and the bore on the diff housing.
4. Use a regular RTV that you would use for a water pump, oil pump or similar, on the flange of the retainer that contacts the housing. Allow proper skin time for the RTV before assembly (basically follow instructions).
5. Tighten evenly to final torque. It's a good idea to slowly rotate the differential inside while inserting the retainer so that the bearing centers and seats properly in the bearing cup. (Put trans in neutral and rotate driveshaft)
6. Allow as much time as convenience allows before filling the diff with oil.
'93 Winestone SS Auto, '91 Pearl White SS.
'93 Pure White SS EJ20G slanty intercooled, SIDESWIPED! In stasis.
'94 FWD and '95 AWD Laguna Blue SVXs.
2017 Pure Red BRZ Limited w/Performance pack
Legacy777
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Re: Rear differential nightmare

Post by Legacy777 »

I'd recommend using the ultra grey RTV silicone. It's recommended in a lot of other places.

http://main.experiencetherave.com/subar ... alants.gif

If everything looks good in terms of "inards" of the diff and bearings, just seal it back up.
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
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