Quick question, my mechanic is asking for my help. I'm shocked to say the least so I'm gonna try my best to help him but I can't find a answer. So maybe someone here will know.

He's got a Eaton G80 unit. It was too big for my 7.5 gm axle. And wouldn't fit the spline on the axle shafts on my buddies 1994 k1500 pickup 4wd which I think is the 8.5 inch 6 lug axle. He has a guy that wants it but he doesn't want to tear the truck apart and find out it doesn't work. What size or make and model truck is this unit for?

Maybe the 2wd fullsize axle is a tad smaller then the 4wd axle. Maybe it for the zr2 blazers since they have a bigger axle. Just wondering if someone knows. Thanks!

 

they changed their diff's from 8.5 to 8.625 in '99 (or was it 2000?). is this what you mean when you saying they have "bigger" axles? 'cause that's the ring gear size you've been quoting, but i know what you're getting @.

have either of you guys thought about just googling the # on the unit to see what application(s) it fits?

 

What I was getting at was that they ran a bigger diff than my 7.5/7.65. Yet wasn't sure if it was the same 8.5 that the fullsize trucks ran or I it was built diffrent.

My mechanic, Jason, is kinda a weirdo. He hates searching the web and reading instructions and things like that. When we did my bodylift he had me read the directions to him as we went along, he's just odd like that. But his work and talent amazes me.

He was going to give me a couple of numbers off the unit so I could do some snoopin' online for him but he got a call and never called me back. I'll get those numbers off him tomarrow and see what I could find out. Since the unit wouldn't fit in my diff or in the 8.5 inch 6 lug in my buddies K1500. I thought it may be for a ZR2.

But he was wondering if the Differential was diffrent between the 4wd and 2wd 8.5 fullsize truck axles. Cause my buddy had a G80 that gave out on him, and this unit he has wouldn't fit his housing or mine. Just thought I'd post it up and see if anyone had any thing like this happen before and maybe knew something I didn't.

BTW, how did I know either you or Swartlkk would be the one to reapond to this post? ha ha.

 

You really have to run the numbers like suggested, GM has many different housings with the same # designations, Depending on the makes or models they're used in.
Example:
As far as the GM 10 bolt 7 1/5-7 5/8 goes, the gear sets in the S-series trucks are the same as the intermediate G-body car line, but differ from the Monza/Vega 7.5 gear sets, all because they changed one of the pinion bearing and race sizes. They do make a special pinion baring and race to make them interchange.
The carriers in all are the same and do interchange as long as it's the same carrier series, and have the same spline count. If the series is different it doesn't mean it won't work in a given differential, it will fit but may require a different ring and pinion to mach that carrier series. If the spline count is different you just need the axles that match that count, then you have to look at the axle length. Somewhere along the line GM put shorter axles in some of the S-series models!!
Everything may look the same but until you know exactly what you have you don't know. And that's true for all GM rear-ends!!!

 

I seem to remember there being a spline count difference between the s-series 8.5" and the fullsize 8.5/8.625 rear diff. Only a few regular s-series trucks outside of the ZR2 got it. If memory serves me, the s-series axles are 28 spline while the fullsize are 30...

What is the spline count on the G80 you have?