Thread: GM rear diff.

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I am trying to ID a rear end in my 89 GMC 2500. It has 14 bolts and no id tags/stamps. I really don't want to open it up yet if I don't have to. I was wondering if anyone knew what was the factory ratio and diameter. Worst case is breaking down and getting direct measurements, but it was worth a try.
anyone got the ratios for a 700r4? electric controlled?

First of all, you are more than due to tear this cover off and inspect the assembly. Cheap insurance for down the road. Not understanding the question, I would advise to count the teeth on both ring and pinion gears. Cross check the VIN and research through means of dealer or internet whether it matches OEM. As far as 700ra ratios, it is the same as non-electric programmed. There was a couple of changes because of planetary mods to slighty affect each gear multiplication through the growth of this tranny The changes are so slight that it really is the same. As I always believe, research the tranny on the internet (Google or ??????) it's best you know waht's under your feet than guess or listen to a bunch of BS from to many "Experts" that heard from their barber's nephew's cousin married to Austin Coil's cousin twice removed who went to Magic Moutain with a friend of somebody's neice.

The 14 bolt gm rear is a full floater of choice for 4x4's. I have one in Frankenbolt, my 4x4 project truck. WWW.pirate4x4.com has a wealth of info on these creatures.

you are right. this truck is new to me and the best way for me to know it is to put my hands on it! I can check the condition of the diff and find out exactly what is there. I am learning that my eyes are better than the barber's cousin's hard of hearing memory.

Try looking here (click bottom right pic.) ---> http://www.700r4.com/faq/faq.shtml

Hope it helps you out.

Pat