2005 Ring Gear Size

GM Dude · March 25, 2007

I posted this in another area with no responses. I figured I may have just posted in the wrong area so I have reposted it here. Don't flame me too bad for reposting.

I have decided to get brave and change out my differential gears from 3.23 to 3.73 in my 2005 GMC Crew Cab because with 20" tires and towing a boat, the final ratio of 3.08 +- is just horrible.

After researching web sites to buy the ring & pinion, they show 8.5 or 8.6 and some show both together as one group. It's confusing because it looks like they are saying 8.5 and 8.6 are the same on some sites. One site states that the 8.6 will always have disc brakes (which mine does not) but do not list the 2005 for the 8.5

Now the question I have for the experts on this site - what size ring gear does the 05 GMC Crew have or how can I comfirm it? It's my only mode of transportation and really would like to order the parts before I tear it down for confirmation. Afterwards I will get a wait4me tune to compensate for the gear & tire changes as well as performance mods. This leads me to my next question, do I have to get something else programmed for the ABS system? If so, will they be able to do that without touching the new wait4me tune?

Thanks

Turnintires · March 26, 2007

first what kind of truck is it 1500 2500 etc and are you talking about the front Diff?

GM Dude · March 26, 2007

first what kind of truck is it 1500 2500 etc and are you talking about the front Diff?

Sorry about that....it's a 2WD 1500 crew cab

TBLAZER · March 27, 2007

I posted this in another area with no responses. I figured I may have just posted in the wrong area so I have reposted it here. Don't flame me too bad for reposting.

I have decided to get brave and change out my differential gears from 3.23 to 3.73 in my 2005 GMC Crew Cab because with 20" tires and towing a boat, the final ratio of 3.08 +- is just horrible.

After researching web sites to buy the ring & pinion, they show 8.5 or 8.6 and some show both together as one group. It's confusing because it looks like they are saying 8.5 and 8.6 are the same on some sites. One site states that the 8.6 will always have disc brakes (which mine does not) but do not list the 2005 for the 8.5

Now the question I have for the experts on this site - what size ring gear does the 05 GMC Crew have or how can I comfirm it? It's my only mode of transportation and really would like to order the parts before I tear it down for confirmation. Afterwards I will get a wait4me tune to compensate for the gear & tire changes as well as performance mods. This leads me to my next question, do I have to get something else programmed for the ABS system? If so, will they be able to do that without touching the new wait4me tune?

Thanks

You should have the 8.6 diff,this replaced the 8.5 severall years ago,3.23 use a different diff case then the 3.73,GM has a case for the 2.73,3.08 and 3.23 a different case is use for the 3.42,3.73 and 4.10,so make shure you are getting the right gears for your truck,some of the aftermarket gear manufactures make two different gears designs to fit either differential case.

The programer should take care of the ABS calibration once you select the right gear ratio and tire size.

GM Dude · March 27, 2007

Thanks TBLAZER....go figure, different axle assemblies for different gearing. I would have thought they would all be the same to make it cheaper for GM.

ZZebes · March 27, 2007

Actually the difference is in the Carrier not the case and i think the split is at 2.73 cause i'm swappin my 3.23's for 3.73's next week and its the same rear just a new carrier

GM Dude · March 27, 2007

Actually the difference is in the Carrier not the case and i think the split is at 2.73 cause i'm swappin my 3.23's for 3.73's next week and its the same rear just a new carrier

Correct me if I'm misunderstanding, are you saying I would have to get a new carrier also? OR are you saying 2.73 and numerically higher (3.42 , 3.73 & 4.10's) all use the same carrier? Have you already purchased your parts and if so, what all did you get?

Thanks

TBLAZER · March 29, 2007

Actually the difference is in the Carrier not the case and i think the split is at 2.73 cause i'm swappin my 3.23's for 3.73's next week and its the same rear just a new carrier

Correct me if I'm misunderstanding, are you saying I would have to get a new carrier also? OR are you saying 2.73 and numerically higher (3.42 , 3.73 & 4.10's) all use the same carrier? Have you already purchased your parts and if so, what all did you get?

Thanks

The case is what GM calls the part the ring gear bolts to,it it's also known as the carrier,not to be confuse with the housing,you don't have to buy a new case/carrier as the aftermarket manufactures make 2 different ring & pinions of the same gear ratio to prevent you from having to buy a new case,just make shure you tell them what gear ratio you have so they now what to give you.