2004 GMC 3500 rear end size question
 

Pulled my Vin number and decoded the options. I know I have a 3:73 rear-end ratio. How do I tell what size rear-end I have? 9.5, 10.5 or 11.5? I'm getting ready to replace the parking brake pads and a axle seal. Tia

Re: 2004 GMC 3500 rear end size question
 

Won't be a 9.5 in a 3500 You can tell right away if you have one of these by looking. The other two axles are full floating so the hubs extend out from the wheel with the bolts holding in the axle shaft. The 9.5 is a C Clip axle like the 10 bolt and 12bolt.

LQ4 gasoline will have the 10.5

The dirtymax will have the 11.5

Not sure about the 8.1L They came with the Allison so it might have an 11.5 out back.

Re: 2004 GMC 3500 rear end size question
 

An easy tell for an 11.5 is that the pinion will have a damper on it. Looks like a harmonic balancer. I know the 11.5 came in 2500HD's I have seen. My swap rear end is from one. I would wager an 11.5.

Re: 2004 GMC 3500 rear end size question
 

You have an 11.5". The only way it could be a 10.5 is if the truck was a SRW with a 6.0. But the 6.0 trucks had 4.10 ratio. So, since your truck has 3.73, we can tell you have an 8.1 or 6.6. So you have an 11.5".

Re: 2004 GMC 3500 rear end size question
 

Thanks for the help! 11.5" it is. Just replaced inner and outer bearings, seals, parking brake pads and changed rear diff fluid. I seem to have a "bounce" coming from somewhere. Shocks are new all the way around. Wondering if the carrier bearing is starting to go out? The best way to describe the "bounce" is after going over a rough road, it seems like the truck suspension feels like I'm driving over washboard. Probably will replace the u-joints and the carrier bearing to see if that helps. Any other suggestions are appreciated.