Replacing Differential Rear Cover: Tips??

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Mar 29, 2007 | 12:37 PM

Wuttin

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Drifting

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From: Hamilton NJ

Replacing Differential Rear Cover: Tips??

Now that I've received my diploma from Bubba Univ for completing my course work in differential rear cover destruction, I need to begin my career as a trained wrench.

Searches seem to come to the consensus that the best way to change out the cover is to remove the pumpkin and the cross member. VB&P seemed to think it's simply a matter of dropping the crossmember 2 inches then reaching around to free the cover from the x-member. I'll try this, but I tend to agree with the CF'ers that the diff has to come out.

Here's the plan: Please confirm and/or edit

disconnect strut rods from the bracket at the differential; leave bracket in place as jacking point.
leave strut rods attached to shock mount, just move out of the way
disconnect the half shafts from the differential side yokes; leave attached to the spindle, just move out of the way also
remove the monospring and associated hardware
loosen cross member and drop while bolts are still in place
leave drive shaft connected to companion flange
disconnect front differential bracket from frame mount
jack up differential and complete disconnection of crossmember from frame
slowly lower differential and ease back so front of drive shaft comes off of slip joint and the crossmember/cover bolts are exposed
keep it all under the car to swap the cover then reverse procedure

Will leaving the driveshaft connected still give me enough room to drop the unit and remove the crossmember? Reattaching the companion flange was the worst part of this job when i did it last spring...no repeat if possible.

Thnx,
Steve

Mar 29, 2007 | 12:48 PM

eastltd

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From: Sault Ste. Marie Ontario

Have you thought about checking the internals of the pumkin when you do this? If you go this far, it may be worth at least changing the seals, cleaning the pumpkin and repainting the assembly before you re-install. If this is the case, disconnect everything off the diff so you can work on it seperately.

Just my 2 cents

Mar 29, 2007 | 12:58 PM

Wuttin

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Drifting

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From: Hamilton NJ

Quote:

Originally Posted by eastltd

The worst part is that I did it all last spring, set for the long haul. Only redoing now it because I damaged the perfectly fine stock cover by upgrading to the monospring. The less I can do to swich out the cover, the better. Torquers beware!

Thnx

Mar 29, 2007 | 04:18 PM

Gordonm

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From: Forked River NJ

Disconnect the driveshaft from the rear end. It will not come down with it still on. Yours is all clean and it should take you about an hour to have it on the ground. Leave the driveshaft in the transmission just disconnect it from the back. I have done this many times and can do it in my sleep now. Take the whole thing out from under the car and get to where you can work on it. You are going to have to remove the crossmember. Remove the X member and I found for cover removal the whole pumpkin fits nicely in a 5 gallon pail with the nose down. This keeps all the fluid in the rear. Just scrape off gasket material carefully and put on the new cover.

Mar 30, 2007 | 09:19 AM

Wuttin

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Drifting

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From: Hamilton NJ

Thanks Gordon...Figured I was gonna have to split at the shaft. Make my life easier in the end I expect.

I was looking through the library last night trying to find the torque spec for the U joint at the rear of the drive shaft to the companion flange on the differential. If I read it right it's 15 ft lbs which seems kinda light. Anyone know what it is for a stock 79 L82 w TH350?

Thanks, Steve

Mar 30, 2007 | 10:35 AM

Gordonm

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From: Forked River NJ

Quote:

Originally Posted by Wuttin

It is 15 ft/lbs. They are small fine threaded bolts and a bugger to get at. I probably tighten mine slightly more than this. This is one of the few that I do not use a torque wrench on. Tough to get the TQ wrench in there and anything below 25 ft/lbs is tough to get a good reading on anyway. I do it by feel.

Mar 30, 2007 | 12:25 PM

Wuttin

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Drifting

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From: Hamilton NJ

Quote:

Originally Posted by Gordonm

They are small fine threaded bolts and a bugger to get at.

I remember all to well...part of the reason I'd rather avoid taking it apart. Live and learn.

Apr 2, 2007 | 09:28 AM

Wuttin

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Drifting

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From: Hamilton NJ

Update:

Turns out it was easy to remove the cover without taking out the entire differential.

left strut rods, driveshaft and halfshafts attached
placed small scissor jack under strut rod mount bracket on the diff
removed spring mounting plate and monospring
backed off crossmember bolts just enough to loosen the unit (it was off last year so broke free from the frame without a fuss)
used the jack to slowly lower the crossmember
removed the crossmember frame mount bolts completely and replaced them with the long spring mount plate bolts (same thread pattern)
removed nut and washer from front differential frame mount so the whole unit could pivot
continued lowering the crossmember/diff combo until I could reach above the crossmember and get to the 4 hidden bolts with a short extension on a 3/8 ratchet. No prob.
removed the long security bolts and the crossmember slid out between the frame and differential cover. Full access to all diff bolts

Granted, I was able to pull this off because eveything was clean and all of the bolts had been recently removed...almost like working on my DD.

The cover, as expected, had a gaping hole where the spring mount bolt blew through the casing, only on one side. Some nice chunks of metal were found in the bottom of the differential case, as well as the metallic puree that used to be fresh gear oil. Live and learn. All the innards of the diff look OK so I'm hoping I didn't do any lasting damage. I'll give a full flush and fresh fluid, slap on the new cover and hit the road!

Enjoy,
Steve