Posi/LSD or open diff.

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evilunclegrimace

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Took my truck to a trusted mechanic to have some work done for a freshly bought truck. We bought it from a friend, 95 Chevrolet k1500 5.7 automatic. Got it back and was told the rear end was a “locker”. So we decided to test that theory out, and got confused. We went to an old backroad to give it some crap. So we did a burnout and sitting still it roasts one tire, but then you let go of the brake and let it move, and the other tire starts to roast with it but not NEARLY as bad, and just for a second. So I’m confused, do we have a locking rear and but it’s needing rebuilt or do I have an open diff?

So you are doing a "Brake stand" or power braking the truck in order to get both wheels to spin, this is out side of the design parameters of the differential. Basically you are abusing the truck in order to get both tires to spin.
The G 80 locker was designed for low traction street/mild off road use, not high torque/racing applications. There are a lot of folks that don't like the G80 because it does not stand up the severe abuse, it was not designed to. Driven in a "normal" manner the G 80 locking differential is a reliable unit for street use, as it was intended. I have personally driven a G80 in a '88 K3500 over 250,000 miles with out any problems. I also drive a '90 K1500 with 170,000 miles as a plow truck that is equipped with a G 80 and have had zero problems with it.
To many people expect the factory to build a truck to stand up to abuse that is not normal and then complain when it fails. Most people do not abuse their trucks/vehicles on a daily basis.(intentionally spinning the tries is abuse, period) While the manufacturer could build a truck/vehicle that would with stand this is type of abuse/"spirited driving" it is not financially sound as it would raise the cost of the truck/vehicle and the majority of people would be paying for something that they do not need or use. This is why the after market industry exists. For those that like to drive "outside" of normal parameters. Flame suit on:flamingdevil:
 

df2x4

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Hoosierlong90

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I have the grizzly locker. It's pretty much the same as the Detroit Eaton but cheaper by like 20$ and has hardened internals with a hell of a warrenty. I like it a lot. It will spin both tire doing a burnout, gravel, mud, but won't break loose going 70 around an offramp in the wet rain, unless I demand it with the skinny pedal. Haha that's my suggestion. The g80 as stated is good for, well not much.
 

thinger2

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And be carefull when you look up any info on a G80 diff.
GM used the same RPO code for all traction control diffs back then so a G80 in a car is a limited slip which does require a friction additive.
A G80 in a truck is an Eaton Gov lock and additives will screw it up.
Also if yours is a 95 you should be okay to run synthetic but make sure.
There is a TSB about synthetic causing leaks but I think that was a mid 94 and older thing because of silicon seals
 

CNRED

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Generally dirt is not the place to find out. Wheels must have resistance to activate the limited slip. There were not active locker rear ends to my knowledge.
 

grey wolf

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I used to be a tech at a GM dealer. I've seen a few of those G80 locker diffs basically explode. As mentioned above, they're not made for taking abuse. When you take it apart and look at the actual mechanism, it's pretty small, you can see why it won't stand up to much abuse, but if it is used as intended, it ought to work just fine. Basically once one wheel spins faster than the other by a certain amount, there's a little weight that pops out and engages the locking mechanism. Also, there are no clutches or anything in that style of locking diff, so there's no need to use limited slip additives. Always a good idea to have fresh oil in any diff though!
 
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