1983 Z/28 with a disc brake rear end. I dont know if its original to the car. 5PQ C0831 is stamped on foward right axel tube. I looked all over for rear end data and came up blank. Help. Also a rear end identification site would be appriciated.

 

There aren't many rears that will fit these cars. If it's all bolted up and all that, then that narrows it down quite a bit.

Count the cover bolts. Tell us how many, there'll be either 9 or 10. Post a pic of the brakes. Since the fluid needs changed, while you're changing it, get a pic of the carrier through its "window", and look on the edge of the ring gear for some numbers like 42:13 for example, which would be the ratio. (42/13 = 3.230769230769230769230769... aka 3.23)

 

Its a 10 bolt and I counted the teeth on ring and then pinion gear(old school way) and came up with 3.07 posi. I just would like to know if its original to the car. The calipers were the type for the lever and spring type e brake attached by a stud coming from rear center of caliper. A po had taken them off and e brake cables for some reason. One side the caliper is in front of rotor and the other side its in back of rotor. Thats why Im thinking maybe it had a drum brake rear and someone swaped this one in. Dont have rpo code sheet or broadcast build sheet.5PQ C0831 is stamped on front passenger side axle tube. Just would like that translated

 

Sounds like a completely normal (and worthless) 10 bolt F body rear. It is normal for the calipers to be front/back like that.

GD

 

GM called it a 3.08...

 

Can anyone decipher the code on the axle tube for me? Or shoot me a link to a site for codes. I find them for 67 up to 81 but not third gen. I know its not hi performance by any means but considering its never been hot rodded and in good shape Im in the process of checking it for originality. I dont have build sheet or the rpo codes sheet.

 

Yup... 82-88 10-bolt. 3.08 gear if it's 13 & 40. The little weenie early-model 26-spline axles.

If it was really a posi when new it's probably an Auburn. If it looks like these, especially the one on the left which is a 2 series such as a 3.08 would come with, that's what it is.



Impossible to know whether it's original to the car, codes or no codes. Wouldn't too much matter one way or another; there's nothing particularly "desirable" about it.

The Auburn is total junk. It fills the fluid with metal dust as it wears, and once it's gone, it can't be rebuilt. They rarely work for more than 50k miles or so, but who knows, you might be lucky.

The cast-iron Saginaw brake system is arguably one of the worst ever made. I'd rather have drums. And yes, it came from the factory with one caliper ahead and one behind; that way they can both be the same, instead of having to be mirror images. Yeah I know, pretty weeeeek, butt hay, it wasn't my idea. I guess at the time it seemed like A Good Idea.

But all that's of little or no consequence. If you had the RPO codes for the car then maybe you could tell if that's what it originally came with, or at least, if it's one of the same that it came with. But rears aren't serialized so "The" "Original" has no meaning.

 

A lot of those early cars, because they had such low-power engines, came with shorter gears in the 3's. So yeah it probably did come with a 3.08 gearset it in. It's still a really weak rear end and the Auburn posi is likely garbage if it has more than 50k on it as Sofa mentioned. It's got weak 26 spline axles, terrible cone-type Auburn limited slip, it's a 2 series carrier, and it has the completely undesirable iron caliper rear discs . So I highly doubt anyone would have *elected* to put that rear in the car for reasons other than simply "repair". Because that's about as far from "performance" or desirability as you can get. You would likely have to pay to have it hauled off if it weren't attached to a car with value.

GD