What differentials do I have
 

I am looking for diff rebuild kits for my 89 K2500 (7200GVWR)

I find a number of different kits for ring gear diameters from 10.50 down to 8.50. The RPO Code is GT4. The wheels are 6 bolt NOT 8 bolt and the diff cover is 10 bolts.

What size ring gear do I have front and rear?

As soon as I know, I will be calling Parts Geek and ordering the kits.

Thanks
Steve

Re: What differentials do I have
 

Should be 14 bolt semi float, 9.5" ring gear. Front is the same as a 1/2 ton, think they are 8.25?? Not 100% sure.....Randy's Ring and pinion can tell you what you have.

Re: What differentials do I have
 

My C2500LD had a 6 lug 14 bolt, but I swapped it out with a 10 bolt. That might be what happened with yours. See if it has a conversion u-joint. Two cups will have an inner c clip and two will have an outer clip, plus the cups are different diameters.

Re: What differentials do I have
 

Under further investigation, I found that the 10 bolt rearend that I got from a 1500 is WAY smaller than the 7200 lb rear under my truck. I am not sure if mine is 12 or 14 bolt, but will check after the snowstorm is over.

Thanks
Steve

Re: What differentials do I have
 

I found after the snow stopped that mine IS the 14 bolt 9.5 rearend.

The parts and ring gear are coming from E-Boy next week.

Next question:

I have a choice between 11 and 13 inch rear brake hardware kits. any guess which size the truck should have?

It is a bit frustrating that the truck is not the BIG full size and not the LITTLE full size but a mix of both with a few parts unique to the 7200 GVWR trucks.