I have a 1986 Firebird with a 350 swap. I'm looking at installing a eaton posi unit in place of the stock internals. I purchased a used eaton posi unit from a 1986 S-10 with the same rear end as my car (10 bolt 7.5" 26 spline). I will be leaving the gears the same. Is it as simple as removing the stock unit and installing the Eaton unit. What exactly goes into this? Do I need to worry about backlash etc?

 

First of all you did not purchase a Eaton Posi from a S10. You purchased a Eaton Governor Lock from a S10. The Eaton Posi was never installed in a S10. These are completely different differentials. The Eaton Posi is a much better differential. The Eaton Governor Lock has earned the name Gov Bomb for a good reason.

Did the S10 have the same series differential as your car? If you have a 2 series in your car and the S10 was a 3 series then this isn't going to work anyway. The 3.08 to 2.14 gears fit a 2 series and the 3.23 to 4.56 gears fit a 3 series.

You will have to set the backlash and bearing preload when installing this. You will need shims to do this. You will also need a dial indicator with a magnetic base to measure the backlash.

 

Yes you will probably need to worry about backlash. Might be OK; more likely, not. Even more likely, the stock (cast-iron) shims, esp the one on the driver's side, are probably SEVERAL .001"s thinner than they started out as, because they wear.

You'll HATE that crap S-10 thing. It's not a "posi" at all, really. What it is, is an OPEN rear (no posi action whatsoever) as long as the difference in RPMs between the 2 axles is less than about 150 RPM. But when that threshold is exceeded, it LOCKS UP with a bang. (literally) with good power and traction, the unit will literally GRENADE; and if you look at the shape of the pumpkin, it's not hard to see where the red-hot sparking shrapnel is going to be directed: RIGHT STRAIGHT INTO the gas tank. (yes it has happened) Even during normal driving, those things are unpredictable and cause all manner of handling problems, esp on wet or otherwise slick streets, due to their sudden and violent operation.

I'd STRONGLY recommend NOT putting that garbage into your car.

 

F***. I bought the rear end for my car and I paid a lot of money for it so it won't be worth installing this gov lock? Can I buy an actual posi unit that will be a direct replacement?

 

The Gov Lock worked OK in stock GM trucks, but that's about it. They don't hold up well to high performance use. You can get an actual Eaton Posi, Yukon Dura Grip, Power Trax Grip LS, Eaton Truetrac and several other good limited slip differentials that fit your car. They will all install the same way. You need to know what your gear ratio is before buying anything. I don't know of any after market 2 series differentials, so if you have a 3.08 to 2.41 rear end you might not be able to find something good that will work in it without changing gears. There are instruction on how to install it in the FAQ about 10-bolts sticky. https://www.thirdgen.org/forums/tran...-10-bolts.html

 

Next time, come ask if it's A Good Idea BEFORE all the rest of that. Kinda hard to turn the clock back and reach back into the past and make a new decision armed with the information you should have got BEFORE taking a left turn down a dirt road and into the weeds, instead of after.

The S truck guys won't even buy those things. One visit to a truck forum before buying it would have told you everything you needed to know about it. Those things are worth less than $50 on the open market.

A better plan would be, sell it to the next "greater fool" (one thing I've learned about the species on this planet that considers itself "intelligent": doesn't matter how great of a fool you think you've found among them, there's ALWAYS at least one "greater fool" out there somewhere) and buy an actual posi. I'd strongly recommend against buying either a 2 series one or a 26-spline one, because those things lock you into inferiority. Better to save up your coins and do it RIGHT, ONCE, put it behind you, have the best, enjoy it forever, no regrets.

 

To clarify a bit, the gov loc has clutches, it acts as a posi but also has the ability to lock up completely at certain speeds, up to 35mph iirc.

On paper it works, the problem is when the clutches wear out, the thing will act more like an open rear and then when it locks it tends to explode.

Either way if its used its probably about shot and its not worth rebuilding or messing with.

 

The Gov Lock has a very small gear on the end of the governor. This gear mates with another gear on a cam plate that applies pressure to the clutches. This small gear breaks easily, and when it does it will no longer turn the cam to apply pressure on the clutches. When this happens the Gov Lock only works as a standard differential and will no longer spin both tires.

In some extreme cases the Gov Lock will break through the center and destroy about everything in the rear end.

 

Here's how they fail.

https://www.google.com/?gws_rd=ssl#q=g80+failure

Look at the images.

Note that quite a few of these are the 8½" 10-bolt instead of the 7½"... doesn't too much matter though, it's the same thing, only difference is, the 8½" produces a few ounces more shrapnel. Otherwise the same.

 

Thanks guys. So I found an entire rear end out of a '82 trans am. It's got disk brakes, posi and 3.72 gears. Will this fit in my car? Do I need to modify anything?

 

If it's the factory limited slip differential then it's going to be the Auburn. No better than the Gov Lock. The Auburn wears out and can not be rebuilt. It fills the rear end with powdered metal that goes through all of the bearings. Check with the owner and see if it has the Auburn or if he has upgraded it to a Eaton Posi, Dura Grip or other after market differential.