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Old 11-24-2009, 07:46 PM
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Used up GM 10 bolt

I think this diff has seen better days. Its been sitting for years, and since re installing (condition unknown) it has begun leaking badly at the pinion. (back end is jacked up higher than the front) Figuring it was tired, I started looking for play...the pinion is easily rocked on its axis as are the wheels to the point where there is an audible click and visible play.

I'm guessing a total rebuild is in order...what else should I be checking for??

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Old 11-25-2009, 07:49 AM
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Which 10 bolt is it? The 8.5 10 bolt is a good rear end and worth a rebuild. If it's the 8.2 or 7.5 then you might want to think about getting a better rear end to invest in.

An installation kit is the best way to go when rebuilding a rear end. It will come with all of the bearings, crush spacer, pinion nut, shims, gasket, seal and other parts needed for the rebuild. You will also want a set of axle bearigns and seals. Check the axles for wear or rust where the bearings run on them. If you see any of these signs then they need to be repalced.

When you get a installation kit be sure that you get a good one. There is a bunch of junk out there and the good instalaltion kits will cost a little bit more. I've used them all and hae some favorites and some that I wouldn't recommend to anyone.
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Old 11-25-2009, 03:08 PM
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there is always some free slop in the pinion

it is the backlash of the gears

has to have some

click is the gear teeth intermeshing

how much free rotation are we talking ?
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Old 11-25-2009, 07:36 PM
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thanks guys.

Big; When you refer to 8.5, is that the diameter of the big ring gear?

Fast68; The slop is terrible....to the point like it feels as if it isnt even bolted on.

the wheels, maybe a clunk is more like it. I can lift up on a tire and see it move. These bearings must be half gone.
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Old 11-25-2009, 08:33 PM
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Yes, that's the ring gear diameter. GM made a 8.2 10 bolt from '64 to '72, a 8.5 from '71 to present (now the 8.6), and the 7.5 from '78 to somewhere in the early 2000s. The 8.5 is the only one that is really strong enough to bother with, and it needs a few modificcations to make it strong. If this rear end is special for something that you have then rebuilding it would be worth while.
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Old 11-26-2009, 08:45 PM
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Quote:
Originally Posted by big gear head
Yes, that's the ring gear diameter. GM made a 8.2 10 bolt from '64 to '72, a 8.5 from '71 to present (now the 8.6), and the 7.5 from '78 to somewhere in the early 2000s. The 8.5 is the only one that is really strong enough to bother with, and it needs a few modificcations to make it strong. If this rear end is special for something that you have then rebuilding it would be worth while.
Thanks, looking at a differential ID guide, its either an 8.2 or 8.5, but since you added the date, I must conclude its and 8.5. (It in an 87 1/2 ton GM PU) According to a haynes manual, it is a locking diff, though I'm unsure if that equates to a posi or limited slip?. Found out the pinion is slopping on the shaft as if the nut was loose. I'll be looking into this a little closer....doesn't look good. I'm hoping its a rebuild candidate...3:08s in it now, like to go steeper
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Old 11-26-2009, 10:44 PM
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The locking differential in the trucks is the Governor Lock. It's a pretty good differential for a stock truck, but you don't want to abuse it much. They tend to break.

The '87 truck rear end will be the 8.5 with 28 spline axles. This is a good rear end and can be built strong. When I build them I usually upgrade them with a 30 spline Eaton Posi and 30 spline Moser axles. This puts them up close to the strength of a 12 bolt.
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Old 11-27-2009, 08:29 PM
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Hey, thanks again Big Gear...Which installation kits would you recommend? I'll likely freshen this axle up (if the shafts are still ok) for now with a kit and new bearings & seals, then the Eaton / Moser stuff as I can afford it. (winter builds). This axle isnt for or out of something special...my wallet can't budge on a 12 bolt (that likely needs a rebuild anyway) right now.

Where would good sources of the components be...PAW, Jegs etc??
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Old 11-28-2009, 06:11 AM
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The best installation kits are from DTS, Tom's Differentials, Dewco and Randy's Ring & Pinion. The Ratech, Summit, Jeg's and others are junk.
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