81 c10 rear end?

Rooster81

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I just bought a 81 c10 I know it’s a 10 bolt but not sure if 7.5 or 8.5. I was told the 7.5 wasn’t much and the 8.5 are far superior. Can anyone elaborate?
 

ali_c20

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Keith Seymore

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It came with an 8.5.

If the original axle is still under there that's what it would be.

K
 

Keith Seymore

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What could I do to beef it up a bit, make it more reliable?
Well - it should be fine for daily use. Maybe do something with the center carrier if it has the "gov-loc" differential.

I've got the original 8.5" ring gear 10 bolt in my Chevelle. It's roughly 1000 HP and goes 9.80's at 3900 lb class weight.

I have to change the ring and pinion every so often but that's with aftermarket axles and a spool.

K
 

TotalyHucked

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The stock 10-bolts are 28-spline, the best bang for your buck would be to call or email Quick Performance and talk to them. I upgraded mine to their 30-spline kit that came with a Yukon Dura-grip clutch type posi unit, your choice of gear ratio and all bearings/seals for like $500 (this was 2-3 years ago, they're probably a little more now). Then I scooped their 30-spline axles and a T/A girdle from them as well. All told is was right around $1,000 for all the parts. I've been beating on the truck for over 2 years now with no issues and know a few guys putting 6-700hp through the same setup
 

Soundmound

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Not to be a thread jacker, but I've got a burning question. My 84 2wd 1/2 ton makes a "clicky/chattery/creaky"(I don't know how to describe it better) sound. Mostly when I reverse and am turning, but no one has been able to identify it. Had the brakes cleaned and adjusted while it was getting the carb done just to see if it was the shoes grabbing. It was not. I hope I'm not due for a rear-end rebuild, but if I am taller gears are a must.
 

Soundmound

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Man! If it was creak/clicky/chatter I could help you,but clicky/chattery/creaky I got nothing
I know it's ridiculous. I just can't find a better way to describe it. I've only been able to get 1 other person to hear it and they couldn't pin it down either. It's maddening I tell ya. I was hoping Keith would just intrinsically know what it was lol.
 

Keith Seymore

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Maybe.

When the rear drums are machined sometimes they leave a little "screw thread" situation. As you drive the shoes are then pulled away from drum until the spring force overcomes the thread and they "snap" back against the backing plate. That results in a rhythmic "click click click" sound while it is exhibiting the problem. Usually it's just one side, and in one direction, because the opposite rotation forces the shoes into the backing plate.

Other than that, if it's in the diff, you can get some clicks and grabbiness from a locking/limited slip diff as it is going around corners. Usually that is fixed by adding the "whale oil" limited slip additive.

K
 
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Soundmound

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Thank you @Keith Seymore! This is much less expensive than the other plausibles. When I read your description I can hear it. I was told rebuild it if I'm skittish, but it's a gov lock and they are noisy- live with it. Rear fluid is of unknown age and condition. I'll put some "Moby1" in as suggested when I service it to CMA. Maybe have a look into the drums too.... I'm curious now.
 

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