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1977 c10 rear differential

1387 Views 9 Replies 6 Participants Last post by  lmsport
Hi guys, I need to install a new differential in my truck. The truck is a 1977 C10 (square body). It will have 3.73 gears.
It is a 12 bolt.

I’m looking for a posi unit.

Do any of you have experience with the cone type carrier style?

Like this one- Auburn Gear Inc 5420105 Auburn Gear High Performance Series Differentials | Summit Racing

Is there another one you’d recommend?

I just want to cruise around town and burn the tires off a bit. I might take it to the strip a few times.
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The Auburn is junk. Stay away from it. The Eaton Posi is MUCH better. The Auburn wear out quickly when abused, it fills the rear end with metal and it can not be rebuilt. Also don't use a Ratech rebuild kit. They are also junk. Use a Yukon, USA Standard or best of all Tom's Differentials kit.
X2 on the YUKON LSD...
The problem with cone-style is that they tend to need lots of limited slip additive, and when they wear out (which will be relatively quickly) they aren't really easy or cheap to rebuild. They're not designed to be rebuilt.

A clutch style posi is a much better option, but it's always working. Not a big deal, but you just need to know that its ability to bias torque is directly proportional to how much you feel it in turns. It also means that you're giving it a little bit of wear every time you turn. Still, a great posi.

Also, don't necessarily listen to the intarwebs about the gov-lock. If you listen to intarwebs lore, it will explode and club baby seals before you even install it. As someone who spent many years working on medium duty trucks, and as someone who spent an equal number of years as a driveline engineer for a custom shop, it's just not true. The gov-lock got a bad name because of people using it in the wrong application. Back in the day, people were looking for a cheap posi that they could throw under their Chevelle to go drag racing. Truck posi units were everywhere, most of them gov-locks. The way a gov-lock works is that it is an open differential until it notices slip. When one tire moves X percent faster than the other, a little centrifugal weight engages the clutches to make it limited slip. What happened at the drag races is that the car would stage, they would stab the throttle which would instantly send one tire into a 60 mph cloud of smoke for a split second, and THEN the posi would engage. Things went boom.

In reality, I've pulled apart gov-locks in step vans, medium duty trucks, light duty trucks and other vehicles with 500-600k miles on them and the clutches look brand new because they were only used in rare slipping situations. Come to think of it... I've never had to rebuild a gov-lock because it broke or wore out, and I've probably taken apart 20-30 of them. I actually actively chose a gov-lock for a 66 Bonneville that had a 500 Caddy used as a tow pig. That was 20-some years ago and I haven't even thought about it since.

So... street, towing, daily driving, gov locks are wonderful. Traction-limited, high spirited, always hooning, gov locks could be a problem. The added bonus to a gov lock is that everyone thinks they're wife-beating, drunk-driving chunks of hellspawn, which means they're cheap. The gov lock diff I bought for the bonneville was the same price as the open diff sitting beside it at the junkyard.
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We call them grenade locks. I have scrapped the blown up remains of dozens of them out of the rear end housings of pickups. I did one Monday that was just wore out on one side, the clutch was so worn that the c-clip came out.
I have never seen a govlock for a 12 bolt truck though. The govlock in the 9.5 axle is a rugged piece and seems to hold up fine.
Don't get the cheap diffs from ebay---the clutch will wear out and the gears and pin are not properly hardened.
Eaton and Yukon are your best value. I prefer the helical gear units for street and pavement use.
I've got several boxes full of parts from Gov Locks that broke or wore out. I don't recommend them for anything other than a stock truck.
Thank you all for your input!
Chevy 12 Bolt Truck Yukon Duragrip Posi USA Gear Pkg

I think I may go with this kit. Any thoughts?

Nevermind. Now it is gone from the site.
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