[Snowboardmaniac]

I ran into quite a a mess of problems trying to change the gear ratio of my 2012 Z71 RWD. The truck came with a 3.73 and I was trying to install a 4.11 ring and pinion. The truck should have a 8.6 inch rear diff according to all ring and pinion manufacturers (Yukon, Motive Gear), however mine is 7.5 inch, no clue why.....

I reordered the a 7.5 inch ring and pinion (prior 09 Trucks) with the proper pinion bearings according to Motive Gear. The ring fits perfectly, however the race of the inner pinion bearing would not fit into the differential housing, the diameter is different....

The tech at Motive Gear was unable to help me out further, says that the differential my truck is wired, it should be a 8.0 or 8.6 inch. At least the parts of a 09 Model year and prior should fit since they had 7.5 inch diffs, but don't.

Anyone has a clue whats going on? Did GM throw a wrong axle on my truck when they manufactured it? Did anyone run into a similar issue before?

 

[Skizzo]

The only 7.5" differential I know of is the one from the front of the truck. Otherwise all trucks had either the 8.0" AAM800 or the 8.6" AAM860 (v8) in the rear.

 

[Snowboardmaniac]

That's why this is so wired. Below is a link to the ring and pinion I reordered. The ring fit perfectly, it's definitely 7.5".

Motive Gear G875410 | Buy Motive Gear Ring & Pinion Gears at JEGS

 

[WV NATIVE]

The only 7.5" differential I know of is the one from the front of the truck. Otherwise all trucks had either the 8.0" AAM800 or the 8.6" AAM860 (v8) in the rear.

I agree with the above statement.

I built a front differential not too long ago and it used the 7.5". I built my rear prior to that and used a carrier for a 8.6".

 

[Skizzo]

@snowboard maniac take a picture of your diff and post it. It may help someone identify if you have a swapped axle or what.

 

[Joe canyon]

The link to the ring and pinion from jeg is the wrong part # for a 2012 Colorado. Here is the correct parts https://www.yukongear.com/productdetails.aspx?ProdID=1355

I think 2004-05 was the last years gm put the 7.5-7.6 rearend into a vehicle.

 

[Snowboardmaniac]

Thanks for all your help!

Here is a picture of the differential. No clue why the pic is upside down..