what is it.

[78C10BigTen]

Can anyone tell me by looking at it what rear i have and what gears it may have? Keep in mind its the stock rear.

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[Honky Kong jr]

12 bolt

 

[78C10BigTen]

I can count that thanks lol

 

[Honky Kong jr]

I can count that thanks lol

Lol you asked that's what it is a GM truck 12 bolt. I actually wasn't being a wise ass .........this time

 

[78C10BigTen]

Lol you asked that's what it is a GM truck 12 bolt. I actually wasn't being a wise ass .........this time

Lol well i know its a 12 bolt. Im not very knowledgeable in rears n gears, is that a good one or just a run of the mill?

 

[Honky Kong jr]

Lol well i know its a 12 bolt. Im not very knowledgeable in rears n gears, is that a good one or just a run of the mill?

It's what they used until the 10 bolt. It will have 30 spline axles and a marginally bigger ring gear then a 10 bolt but there are a few things a 10 bolt has ove the 12 bolt too.
12 bolt 8.875
10 bolt 8.5

 

[78C10BigTen]

It's what they used until the 10 bolt. It will have 30 spline axles and a marginally bigger ring gear then a 10 bolt but there are a few things a 10 bolt has ove the 12 bolt too.
12 bolt 8.875
10 bolt 8.5

Are they durable? Are they junk? Are they popularly looked for?

 

[Honky Kong jr]

I have a 12 bolt in my black truck, all be it it has a posi in it and it was cheap. If I would have found a posi for the 8.5 first I'd have a 30 spline 10 bolt in it. Strength differences are marginal between the 2. Carriers are what makes the 12 bolt a pain in the ass.

 

[1987 GMC Jimmy]

Assuming it the gearing hasn't been changed, the RPO sticker is what you need to look at. The code GU* should be the gearing it came with, and if it came with limited slip, it should have a G80 code. For example, mine is a GU6 (3.42) and a G80 (Eaton Gov-Lock).

 

[78C10BigTen]

Assuming it the gearing hasn't been changed, the RPO sticker is what you need to look at. The code GU* should be the gearing it came with, and if it came with limited slip, it should have a G80 code. For example, mine is a GU6 (3.42) and a G80 (Eaton Gov-Lock).

It does say G80 but thats all i see.

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[1987 GMC Jimmy]

You're right. I guess they didn't want to tell you. My sticker is the one with just the codes listed and not the definitions, though, so I don't know if that makes a difference. I guess you'd have to count the ring gear teeth and divide by the number of pinion gear teeth to get the ratio if you plan on servicing it anytime soon. I know you can also find it by turning the driveshaft turns compared to how many turns the wheel makes or something like that, but I can't remember the trick for the life of me. Hey, but welcome to the positraction club. That's pretty cool.

 

[78C10BigTen]

You're right. I guess they didn't want to tell you. My sticker is the one with just the codes listed and not the definitions, though, so I don't know if that makes a difference. I guess you'd have to count the ring gear teeth and divide by the number of pinion gear teeth to get the ratio if you plan on servicing it anytime soon. I know you can also find it by turning the driveshaft turns compared to how many turns the wheel makes or something like that, but I can't remember the trick for the life of me. Hey, but welcome to the positraction club. That's pretty cool.

That is the glove box sticker, i was told it had one on the inner fender but it doesnt. So that g80 means it shouldnt be a 1 wheel peeler? Lol

 

[Honky Kong jr]

I don't think the gov- bomb was in the 12 bolt that should be a clutch type posi. +1 for a good posi and + 1 for 30 spline axles.

 

[shiftpro]

I have a 12 bolt in my black truck, all be it it has a posi in it and it was cheap. If I would have found a posi for the 8.5 first I'd have a 30 spline 10 bolt in it. Strength differences are marginal between the 2. Carriers are what makes the 12 bolt a pain in the ass.

!
Wear good boots, you'll need them.

 

[Honky Kong jr]

!
Wear good boots, you'll need them.

Meh hes only got a small block it will be fine and mine is going in low traction mud. Lol