Rear End Swap

[76C10Stepside]

My '76 C10 has a 12-bolt non-posi rear end Have not had it apart to check tolerances, but it has seen better days. This truck has wide performance radials on all four corners, but still gets terrible traction when unloaded. It loses traction very easily on wet roads, and the rear brakes lock up very easily. I just drive it normally, no drag racing for me. The left brake has a history of auto-tightening on its own, and the drums are at their limits (probably why the brakes tighten up). In contrast, my '89 S10 longbed with ABS and the optional sport suspension handles and stops awesome for a truck.

Am considering replacing the entire rear axle unit with a better one that has positraction and better brakes, if there is such a thing. Is there a later range of years that you can recommend getting a donor rear end from that I can do a direct swap into my C10?

[mcmlxix]

I was just researching a 1994-1996 Impala SS /9c1 Caprice rear axle swap. 5x5 bolt pattern with factory rear disc brakes and built in e-brake (unlike most brakec onversion kits.) I cant seem to find the axle width from wheel mounting surface (WMS) to wheel mounting surface for the truck or the Impala. You would need to add the correct spring perch and an adapter for the brake line because I think they were metric fittings by then.

[76C10Stepside]

Originally Posted by mcmlxix

I was just researching a 1994-1996 Impala SS /9c1 Caprice rear axle swap. 5x5 bolt pattern with factory rear disc brakes and built in e-brake (unlike most brakec onversion kits.) I cant seem to find the axle width from wheel mounting surface (WMS) to wheel mounting surface for the truck or the Impala. You would need to add the correct spring perch and an adapter for the brake line because I think they were metric fittings by then.

Interesting. I was thinking more along the lines of a later year C10, hadn't considered using a car axle. Probably doesn't matter, since it's just a half-ton truck, but I plan to keep this truck "a real truck" that can haul loads and tow cars, not turn it into a hotrod, except for the car tires and 3-inch drop shackles I installed to get the tail to sit a little lower. For the brake upgrade, I was thinking more like better drum brakes. I think disc brakes would work TOO good in the back with no load (the usual). The drums already lock up way too easily.

[mcmlxix]

You can add an adjustable proportioning valve to turn down the rear bias so the front locks up before the rear would. The Impala SS (or 9c1 cop car Caprice) was a heavy car meant for sever duty. I wouldn't have a problem running that rear with a nice posi in a 1/2 ton truck. I just picked up a 78 2wd Blazer and was thinking of going this route.

[76C10Stepside]

Originally Posted by mcmlxix

You can add an adjustable proportioning valve to turn down the rear bias so the front locks up before the rear would. The Impala SS (or 9c1 cop car Caprice) was a heavy car meant for sever duty. I wouldn't have a problem running that rear with a nice posi in a 1/2 ton truck. I just picked up a 78 2wd Blazer and was thinking of going this route.

Good point about using an adjustable proportioning valve. I'd be interested to know how this route works out for you. Width the same? What mods were necessary to make it work? How much did the donor part cost you, and what parts did you have to replace on it to get it in good shape?

FYI, an area search of auto parts on CL for caprice, impala, roadmaster or 9c1 found a pair of front brake assemblies and a few wheels, that's all. All the wrecking yards around here are a joke, never have anything I'm looking for.

[bbbc10]

impala ss rear end is narrower than the c10 rear end an the caprice rear end is even narrower than the impala...I don't see why you would want to keep drum brakes when disc are better....impala/caprice rear ends come with 3:42/3:73 gears posi unit an of course disc brakes.....only need to add leaf spring mounts an a u joint

[bbbc10]

http://67-72chevytrucks.com/vboard/s...d.php?t=417493

[andrewmp6]

Bolt in axle you have zero options on that,Some others will fit but you gotta weld on new spring perches and shock mounts.I would have a lsd installed in your 12 bolt and do a disc brake swap on the rear.Maybe throw on a set of traction bars if needed.

[76C10Stepside]

Thanks for the feedback.

This truck sat from the end of last summer until last month. Since I started driving it again, I've had a "funny feeling" about the diff. Yesterday, I found that the diff vent hose has a hole worn through it from the exhaust pipe.
I suspect this has contributed to corrosion and excessive wear in the diff.

I already know it needs new brake drums, and suspect the diff and possibly the wheel bearings are pretty worn out. Figured swapping in a less worn out rear axle assembly would be easier than fixing all that stuff.

I would be happy with a fully compatible rear end with decent set of drum brakes that don't grab or tighten on their own. My S10 has the heavy duty load and towing options, but only has a light-duty hitch, so the C10 gets all the towing jobs.

[Tom]

You can either swap in another 73-80 12 bolt or a 81-87 10 bolt, otherwise nothing is a direct fit. They all have drum brakes that will work just fine when serviced correctly with good parts. The oem posi units will be decades old at this point, you might want to consider adding a posi to your current axle and rebuilding the brakes.

[76C10Stepside]

Originally Posted by Tom

You can either swap in another 73-80 12 bolt or a 81-87 10 bolt, otherwise nothing is a direct fit. They all have drum brakes that will work just fine when serviced correctly with good parts. The oem posi units will be decades old at this point, you might want to consider adding a posi to your current axle and rebuilding the brakes.

Thanks, Tom. Other than only having 10 bolts on the diff cover, are the 81-87 units the same (non-metric)? Know a good place to get a bolt-in posi unit for my original diff? Didn't find one on LMC's site.

[bbbc10]

a place called summit racing....

[76C10Stepside]

Oh, OK. Hadn't thought of summit. They have two units by Auburn Gear, $429 (3.73 or higher gear ratio) or $475 (2.76-3.42 gear ratio). Not sure what ratio I have.

[77 Big 10]

My opinion, If the axle is that old, I'd change the ring and pinion too. So decide what kind of ratio do you want/need, and get the locker for that.

[Domer]

As for the proportioning valve with 4 wheel disc brakes. We just finished up my buddies 72 with 4 wheel wilwood 14" rotors and 6/4 piston calipers. once adjusted, that thing stops flat with hardly no nose dive, oh and damn quick..

[andrewmp6]

It depends if you want to stay with a stock ratio or want something a little better?If im replacing a diff i would replace the gears also since they are old enough and why do it twice.What trans do you have and do you plan to keep it or upgrade later on?

[mcmlxix]

Originally Posted by J Knight

My 82 10 bolt was 64.5in from WMS to WMS.

Well this answers one question and I believe I found the info on an Impala SS forum stating the SS rear is 63" and the 9c1 rear is 61.5" wide. Wagon rears are wider but no disc brakes.