Are all Gt4 G80 differentials the same size and are they interchangeable?

 

Welcome to the forum!

As far as I know, all non ZR2 rear ends should be interchangeable. The Z rear ends are wider, and are the 8.5" ring gear.

 

There were a few non-Z 4x4 rear axles that were the 8.5/8.6 diffs, depending on options. So you'll need to watch whether the diff is the 7.5 or the 8.5/8.6 diff, and you'll want to watch widths too. 2wd are more narrow than non-Z 4x4, and the non-Z 4x4 is more narrow than the ZR2. All factory ZR2 rear axles are 8.5/8.6 ring with GT4 gears and G80.

 

Man, how could I forget the 2wd vs 4wd widths? My bad

 

The zr2's are not all 8.5 inch ring gear, cant remember if the 8.5" ended with the 99 or 00 m.y. Zr2, but i know for certain the 01/02 zr's all have an 8.6" ring gear in the rear and the front was changed from a 7.2 to a 7.25 and are not interchangable despite having only .05 and .1 of an inch difference. There was no change to the front ring gear size in the 03 zr2's, but the rear was enlarged slighty to 8.65 inches. Only one ring gear was installed in every zr2 after gm changed to the 8.6/7.25 ring gear size, and converting a 3.73 to a 4.10 can be done on the cheap If you reuse the ring gear(only possible when the ring gear shows zero signs of wear) and swapping out the 11 tooth pinion gear for one with 10 teeth. This will not work if you have a non zr2 with the gt3 option's 43 tooth ring gear so dont try it, applies to the 40 tooth ring gear inside every 7.25-8.6/8.65 zr2 only.

 

Breakpoint for 8.5 to 8.625 ring gear was mid-2000. Primary differences between 8.5 and 8.625 - This bigger ring gear 10-bolt went from 28 to 30 spline axles, the carrier spins on what amounts to 12 bolt bearings, the pinion seal rides on a slightly larger diameter yoke, and the gears were made with a modern 2-cut process that reduced the backlash used. When you build an 8.625 you use an aftermarket 8.5 ring and pinion. If you replace the differential carrier, the aftermarket (for example an Eaton clutch type Posi) 8.5 carriers are made to fit the 8.625 housings with standard 12 bolt carrier bearings (If you fit an 8.5 Eaton posi carrier in an actual 8.5 housing, you have to use special carrier bearings). Of course you have to specify the correct number of splines for the spider gears. You can use an 8.5 pinion in the 8.625 housing if you use the 8.5 pinion seal. There are no carrier bearings made that will allow you to use a factory GM 8.5 carrier in a 8.625 rear.