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Differentials-rear ends for dummies

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Old March 9th, 2012, 01:23 PM
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Differentials-rear ends for dummies

Assuming I get the body removed, I then am planning on reconditioning the rear end, along with new rear control arm bushings (upper and lower), shocks, springs, axle bumper, new axle bearings and seals, new body bushing , new brake lines/clip kit(what else am I missing?), and need some general guidance and recommendations, please. I have a 72 Cutlass S-Holiday, open. I am assuming (have not taken them out yet) that the axle bearings are pressed on, and will need a machine shop to repress the sleeve, bearings and put new seal on. 1) Do I re-use the bolt-on retainer to the axle hub, or are there new ones? I have looked on-line and can’t seem to match up some. Plan to use an A9-National bearing/sleeve and a #712146 seal. 2) On the control arms-rear upper and lower, are ALL the replacement bushings the SAME size, even the ones in the axle housing? I will need 4-2 piece kits (I assume Moog K5161 will work all around), and understand that the upper control arm bushings are not “normally” replaced (you buy new arms), but…that they can be removed and new ones pressed in? Please advise.
On the body bushings, it looks like there 4 with bolts and two rebounds-each sided (rebounds near rear passenger’s feet area on frame, and one over the rear axle/high trunk area. 3) What kits works for this? I think I need 12 main upper side bushing (4 of these 12 used as rebounds), 8 spacer bushings (lower frame area) and 8 bolts/washers. A 20 piece bushing kit…Is that correct? Whose rubber kit is the best?
Once I get the rear end exposed, not sure what to do about re-conditioning (if needed) the differential. The car was in California most of its life, and has 89K, or 189K miles on it. I think the ratio is 3.09, something slightly different they made only on California cars. Assume there are several steps in overhauling the box, but I am not really capable to do this. What should I look for (in general) after the cover comes off, and/or do first? The car is NOT running, and won’t for a while. I would “hope” that the ring and pinion do not have to be replaced (expensive little items, are they?). There appears to be a master-overhaul kit (pinion bearings/seals/shims), and then if needed, new spider and side gears. Any thoughts on this? Appreciate your input and ideas.... send some restor pcitures soon...its goings slow.
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Old March 11th, 2012, 05:47 AM
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No diff expert here, but have worked on a few. If you're messing around changing ring & pinion gears, you'll be needing to do some important measurments and shimming. Had an old Pontiac, where a pinion gear welded itself itself to the shaft, snapped the bolt, and was turning inside the center section, wearing on it. Also, good chance the center section bearings are badly pitted, and a bear to pull off. If the axle's a posi, good idea changing out the clutch pack. If not, good time to convert it. If not already, good idea getting a service manual. I have several manuals, and the 1000 page GM manual for my car, that shows everything. Another tip. I use posi rated gear oil, and don't use the seperate additive. Did this before, and while cuts down on clutch pack chatter around turns, also takes away most of the lock up action too. Never again.
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Old March 11th, 2012, 11:45 AM
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thanks Delta, will take all this into consideration. It's not a posi...Alot of money to upgrade. Any other thoughts on the axle bearings, etc? do they seem logical/correct?
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Old March 11th, 2012, 05:08 PM
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Actually, never replaced the wheel bearings/seals on my 77' but maybe should have. With the milage your car has on it, probably not a bad idea. Was just a kid, when going to recycle yard, picking up a 3.73 posi axle from a Camaro. With research, borrrowed some measurement tools, and swapped out the whole innards, from what was once a 2.56 open unit. Somehow managed to do it right, as been hammering on it pretty good, with a custom built 455 for years. When messing around with press fit bearings, some Loctite bearing mount compound's, a good thing to have, as some don't fit so tight. Car has a 700R4 od lock up tranny in it now, so even a little lower highway cruising rpm, than the original 2.56. Real nice combo.
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