How to tell if I have limited slip?

[DnS421]

I have a 1981 Scottsdale, 4x4. I have pretty bad leaks in the front and rear diffs and was going to drop the covers and get everything cleaned up and new gear oil put in tomorrow but I don’t have any sort of tags or anything on my diffs and have no idea at all if I need limited slip additive? Any help is appreciated I will attach pics of my front and rear diffs in case that helps.

 

[AyWoSch Motors]

I have a 1981 Scottsdale, 4x4. I have pretty bad leaks in the front and rear diffs and was going to drop the covers and get everything cleaned up and new gear oil put in tomorrow but I don’t have any sort of tags or anything on my diffs and have no idea at all if I need limited slip additive? Any help is appreciated I will attach pics of my front and rear diffs in case that helps.

If you still have the original spec sheet in the groove box, itll most likely say if you do or not.
Most likey you have an Eaton Mechainal locker (type of Limited Slip). An additive will be helpful for that if that's what you have. I used it in my eaton, and it helped it.

 

[nvrenuf]

The front would not have a factory L/S, it wasn’t offered.

 

[DnS421]

@AyWoSch Motors i don’t have any of my factory diagrams or data sheets. Truck, engine bay, inside of the cab (including the glovebox was all painted and all stickers were removed by previous owner.

 

[AyWoSch Motors]

@AyWoSch Motors i don’t have any of my factory diagrams or data sheets. Truck, engine bay, inside of the cab (including the glovebox was all painted and all stickers were removed by previous owner.

Bummer.
Well as far as I know, theres no way to tell what you have until you pull off the cover. You'll know as soon as you do though

 

[Turbo4whl]

The GM G80 differential is not a limited slip, it is a locking differential. Yes it has clutches but does not require an additive.

Use 80W-90 or 70W-90 gear oil. Old oil seals may not like synthetic oil.

When you pull the rear cover to replace the oil, the G80 looks like this:

You must be registered for see images attach

To test for a G80 without looking inside, jack both rear wheels off the ground. Trans in park or manual in gear, spin one wheel by hand fast. The G80, if working correctly, it will lock.

 

[AyWoSch Motors]

The GM G80 differential is not a limited slip, it is a locking differential. Yes it has clutches but does not require an additive.

Use 80W-90 or 70W-90 gear oil. Old oil seals may not like synthetic oil.

When you pull the rear cover to replace the oil, the G80 looks like this:

You must be registered for see images attach

To test for a G80 without looking inside, jack both rear wheels off the ground. Trans in park or manual in gear, spin one wheel by hand fast. The G80, if working correctly, it will lock.

My G80 is permanently locked.

 

[AuroraGirl]

My G80 is permanently locked.

is that when it makes the granola noise or the kid with wet sneakers on a waxed gym floor who also feeds on attention

 

[AyWoSch Motors]

is that when it makes the granola noise or the kid with wet sneakers on a waxed gym floor who also feeds on attention

More like the kid with sneakers, lol..
The rearend itself is quite, but when I take a corner, it barks like a dog. It either drags the outer one a bit, or spins the inner one.
It's like I have a spool or a locker, which on a shortbed isnt great.

 

[scrap--metal]

Trans in park or manual in gear, spin one wheel by hand fast. The G80, if working correctly, it will lock.

We used to look for the G80's in the junkyard kinda like that. With the truck out of gear, you could rotate one tire and then quickly rotate it in the opposite direction. If the G80 was present and working, the other tire would lock with the one you're manipulating and begin to rotate in the same direction. I cant recall if the direction of rotation was important.

Wayne's method in gear may be easier. We usually didn't get to messing around with the gear selector in the junkyard because most trucks didn't have keys to unlock the columns.

Then the pick and pulls quit letting us disassemble their rear ends and only wanted to sell us entire rear axle assemblies. That put an end to the G80 hunting. I still have one of them from a 'burban in a good Monte Carlo rear end.