Posi Differential for 1972 C10

[skydiver]

Hello All,

I am looking for some advice on rear differentials for my 1972 Chevy C10. I am looking to swap out my standard 12 bolt non-posi differential for a posi. Does anyone have experience with this? What should I look for in buying a posi differential? What type of information do I need to make sure it will fit my truck? I have seen that there are different numbers of splines, how do I tell which number I need? Also, is this something that can be done in my garage or do I need special tools, etc. Any advice will be helpful.

Skydiver

1972 Chevy C10 LWB
350 4 bbl

[68GMCCustom]

I just went with an Eaton posi and 3.73 gears in my 12 bolt. The Eaton is both rebuildable and adjustable. Had someone else do it all for me though though.

[68350]

depending on the gears, that will determine which series carrier you need(I believe only the series 3 and 4 are used for stock geared trucks). I would go with an eaton posi, seem to be about the best all around posi set-up. New gears wouldn't hurt, either. While you're at it, if there are any worn seals or gaskets or anything that's not in very good condition, you might as well replace it. I am not sure if you need any specialty tools, but I'm gonna say no, it is something anyone should be able to do in their garage. U might try to find a book or video to help with the process if you're doing it buy yourself. hope this helps

[70GMCer]

There are two areas I do not tackle, rear end setups & front end alignments. It is advisable to have a shop do it. The wear pattern needs set correctly with shims. Also you might need other parts like a new pinion bearing, etc. You want this done right the first time. Posi units are not a cheap thing just too throw in and go.

[Psycho71]

Like others have said, the Eaton is a good unit. Or they get their share of compliments anyway.

For 3:73's or numerically higher gears, you'll need a 4 series carrier.

For 3:42's and lower, you'll need a 3 series.

You'll need a unit for a 12bolt Truck rear end. It will have 30 splines, if I'm not mistaken. They are not the same as the carriers for cars. Well, I think a few of them cross over, but you'll want to specify "truck" just to make sure.

You can get the higher ratio gears to work on the 3 carrier, but they are different and cost a little more.

As far as setting them up goes, you might want to have a shop do it. You'll need a pinion depth gauge, and a dial indicator on a magnetic base.

You can do it yourself, I did my own. But mine was just a carrier swap, so the pinion never moved, meaning I didn't need the depth gauge. I downloaded instructions from Richmond's site, and followed them to the "T", and everything works great (and has for two years now). So it's not impossible. There are a few tricks I've learned since then, and will employ on the next swap. Getting my wear pattern right was actually pretty easy to do. But again, I never had to move my pinion from the stock location. I'm sure it gets much more complex if that's necessary.

There are also lockers available. This would be a good idea if your not changing the gear ratio. As they just replace the spider gears in your stock carrier. They usually cost less too. Some people complain about a ratcheting/popping sound they make when cornering, but Richmond makes one now they "Claim" doesn't do that. It's called the Powertrax Unit. They say it installs in about an hour with no special tools. But again, it's only a viable option if you just don't want to upset the gears. If changing gears too, I'd go with a complete carrier replacement unit myself. Like the Eaton.

I'm probably going to try one of the lockers later this year, just because I don't want to have to set-up my gears again. I should have put a new unit in when I did them two years ago, but the money just was there at the time.

Good luck,
Jay

[nightmare]

Originally Posted by Psycho71

You can do it yourself, I did my own. But mine was just a carrier swap, so the pinion never moved, meaning I didn't need the depth gauge. I downloaded instructions from Richmond's site, and followed them to the "T", and everything works great (and has for two years now). So it's not impossible. There are a few tricks I've learned since then, and will employ on the next swap. Getting my wear pattern right was actually pretty easy to do. But again, I never had to move my pinion from the stock location. I'm sure it gets much more complex if that's necessary.

Don't mean to step on anyone's toes, but Jay, when you did just the carrier swap, did you have to shim the carrier any? I basically did the same thing, and my pinion didn't move, but I didn't do anything else but pull the carrier, move the ring to the other carrier, and reinstall it back in the rear. I haven't put the axle into use yet, but will be soon, and don't want to have to pull it back out because I messed something up. I checked for a wear pattern, by doing chalk on one of the teeth, and it showed to be in the middle. Should this be fine? Thanks for the input.

Mike

[Wasted Income]

Originally Posted by nightmare

Don't mean to step on anyone's toes, but Jay, when you did just the carrier swap, did you have to shim the carrier any? I basically did the same thing, and my pinion didn't move, but I didn't do anything else but pull the carrier, move the ring to the other carrier, and reinstall it back in the rear. I haven't put the axle into use yet, but will be soon, and don't want to have to pull it back out because I messed something up. I checked for a wear pattern, by doing chalk on one of the teeth, and it showed to be in the middle. Should this be fine? Thanks for the input.

Mike

[Psycho71]

Originally Posted by nightmare

Don't mean to step on anyone's toes, but Jay, when you did just the carrier swap, did you have to shim the carrier any? I basically did the same thing, and my pinion didn't move, but I didn't do anything else but pull the carrier, move the ring to the other carrier, and reinstall it back in the rear. I haven't put the axle into use yet, but will be soon, and don't want to have to pull it back out because I messed something up. I checked for a wear pattern, by doing chalk on one of the teeth, and it showed to be in the middle. Should this be fine? Thanks for the input.

Mike

Yes, I did have to play around with the shims to get the wear pattern correct, but it was pretty easy to do. I did actuallly replace all the bearings as well. I just re-used the pinion shims so it went back in the same location it had been, then it was just a matter of geting the carrier shimmed to where the wear pattern was good. The hardest part was adding the extra shims to get the preload on the bearings. .010" doesn't sound like much until you try stuffing the carrier in a whole where it don't want to fit.

I did have my rear end out of the truck, so I know that alone made mine easier.


Jay

[Wasted Income]

It's not that hard to set up a ring and pinion. There is plenty of info online. Just take your time, and check your measurements. It's not a black art