What Differentials Do I Have?

uniteam · June 16, 2008

Hello,

How can I know what kind of differential has my GMC Sierra 2002 1500 HD Crew Cab short bed 6.0L 4x4 Automatic.... ??

My last VIN 8 digits are 2F137113 and the first 3 are 1GTG

I'm running 37x12.50R17 Mud Tires and I want to change the axle ratio, I guess it has 3.73 now, but I need the axle model to find some 4.56 ...

What do you think ??

Thanks for your help...

Rensch100 · June 17, 2008

Look at the front of the diff right behind the yoke and u-joint, if there is a bearing cap with six bolts in it, its a 10 1/2 or larger. I would bet it is going to be a 9.5 semi floating. from 99-04 most gmt800 trucks 1500hd and 2500LD rant the 9.5 semi floating. 9.25 front axle.

Rensch100 · June 17, 2008

4.56 great choice, every truck that is going to pull or have 33+ inch tires it should be required.

uniteam · June 17, 2008

thanks for answer...

Here is a picture of my rear end....

according with this information, and your clues.... I guess it is 9.5..what do you think ?

"GM CORPORATE 14-BOLT

The "small" GM 14-bolt has a 9 1/2-inch ring gear diameter. It was used in the rear of 1964-and-later GM pickups, and in the rear of 1984-91 3/4-ton Suburbans.[/"

But, about the front axle.,.. are you sure it can be 9.25 IFS ??

What do you think?

Riverjet502 · June 18, 2008

I guess I didn't realize there was a 9.5 in 14 bolt. I always thought they were all 10.5 in. So there is a difference say between a 3/4 HD & 3500 in the rearends?

95Sierra2500 · June 18, 2008

I guess I didn't realize there was a 9.5 in 14 bolt. I always thought they were all 10.5 in. So there is a difference say between a 3/4 HD & 3500 in the rearends?

I don't know about the NBS trucks, or even the lower GVW older 3/4's, but the only difference between the rear axle on my '95 2500 (9200lb GVW) and my dad's '94 3500 dually is the length of the axle tubes...Otherwise they're identical, internally and externally.

Rensch100 · June 19, 2008

I guess I didn't realize there was a 9.5 in 14 bolt. I always thought they were all 10.5 in. So there is a difference say between a 3/4 HD & 3500 in the rearends?

I don't know about the NBS trucks, or even the lower GVW older 3/4's, but the only difference between the rear axle on my '95 2500 (9200lb GVW) and my dad's '94 3500 dually is the length of the axle tubes...Otherwise they're identical, internally and externally.

To answer 1 question You do have a 9.5 rear axle on your 1500HD.

99 and up only the 2500ld and 1500hd which are the same thing use the 9.5. The fram on the 2500hd's and up are heavyer after the rear wheel as well.

TO answer the second question alot of the older 3/4 tons came stock with the 9.5 semi floater. Alot of them were ordered as an option with the 10.5 full floating. In the 01 and UP GM's the 3/4's and 1 tons basically run the same axle. The ten and half is not being used anymore. THey went to and 11.5 and I think they will probally be going to 12.5 with the D-max. in the 88-2000 clasic style if all 8600lbs and up vehicals were full floating.

Full floating is nice, but don't be afraid of the 9.5 semi floater. I have one in mine with firestone air-bags (sense i'm the lead tech at a firestone) I have pulled a 35 ft horse trailer with a camper setup in the front end, It worked my 6.0l like never before. I took it across the scale and my gross weight was 22,880. On the pickup I had 12,800. Then I desided to weight the truck alone. 6000lbs So I had an xtra 5,800 lbs on the truck. I wouldn't recommend pulling that much 16,880 with out a 4.56 ratio if you are going threw hills. I am trying to deside if I want to upgrade trucks or no. I just rebuilt my transfer case and fixed the holes in it. If I deside to keep it and make it a play toy, I am going to swap the 4.10's with 4.58 or 4.88 havn't desided, and put a turbo on it. It's not always fun to play with your own vehicals when you fix the damn things all day.