The rear end on my '87 IROC is the only really rusty part of my car - it's REALLY bad. So, I want to replace it.
I can't find a posi disc rear end locally (Los Angeles, CA). I did find a 3.08 drum posi rear, so my question is - can I swap parts from my disc rear onto the drum to convert it to disc?

I apologize in advance if there is a sticky about this somewhere, I didn't see one...

 

Yes, but you'll have to modify the drum rear end's axel flanges. The following link will provide an idea of what is required:

https://www.thirdgen.org/tech/ls1reardisc.shtml

JamesC

 

You sure can do this. My dad Dyno Don has done it several times. It requires modification as described above; its not a direct bolt on.

 

For a direct bolt on - you could go 4th gen rear - but you'll either have to 1) get 4th gen rims and spacers for the front, or 2) deal with the extra width of the axles in the rear. I got a 4th gen LS1 rear with 3.42 posi and disc brakes for $175 here - and the extra 1.5inch width on each side doesn't bother me, especially for the price and getting a posi disc rear - but I also got the 4th gen wheels from same guy for $100 with tires, just in case I change my mind in the future and want the rear wheels tucked back in the fenders.

 

That sounds like a good deal. My car came from the factory with a posi disc brake rear end, but it's making noise and really badly rusted, so I just want to replace it. Since the 3rd gen one's are in somewhat short supply around here it seems, I think my best option is to take my hardware and bolt it onto a drum rear end.

However, you idea isn't bad, and if I weren't keeping my stock wheels, etc. I woud probably consider it. Thanks!

 

You'll also have to turn down the axle hub of the drum brake axles. By 'hub' I mean the flange where the wheel studs are.The OD of the hub on the drum axle is 6" while the OD of the disc brake hub is 5.850". Without turning them down the rotors don't fit. Found this out the hard way last weekend trying to put 28 spline axles from a drum rear into a rear that has disc brakes

 

Oh, I had no idea. Having Dyno Don do it for me is sounding better and better!

 

You can keep your stock wheels with the 4th gen rear - it's just that the rear wheels stick out of the fenderwells about 1.5 inches farther on each side - not 1.5 inches out of the car, just 1.5 inches farther out - which puts them right at the edge of the fender.

You need spacers only to put the 4th gen wheels on your third gen, and then only in the front - the rear axles are longer, but the 4th gen wheels have more backspacing, thus they end up farther inside the fender. But the increased backspacing on the 4th gen wheels puts them too far inside the front fenders, thus the need for spacers in the front only.

Maybe my last explaination was confusing - hope this better explains it.