Rear Diff

vertikal · May 27, 2009

I'm not really sure what differential is in my truck(2004 chev,6.0,auto,lt quadrasteer towing package) but seems as I was told it maybe an 3:88? It came w/265/16 tires but replaced w/285/16's and I'd like to find out if I could place a lower gear in rear diff. and it not affect front diff. Not sure if enough room in quadrasteer rearend to make a lower gear swap...I heard to determine what you need divide the # of tire size you have to tire size you changed, then multiply that by differential size and theororetically it gives you the diff. size you need for larger tires, given this I may need to go to a 4:88 instead of 4:10 ratio, or place the smaller tires back on truck cause I tow a fifdthwheel and need all the power I can get.....plan on k& n air filter sys., the transmission coolerw/fan and thermostat (175 degrees), then possibly a power chip...as Ive heard by doing this you can increase h.p. by up to maybe 20% or more...any of this make sense to anyone?

vertikal · May 27, 2009

also the tow rating Ive came up with on my 2004,4x4,2500lt crew cab w/6.6 in. bed (short box) is 9440lbs., if anyone knows of a more correct number please respond, thanks

Zembonez · May 27, 2009

also the tow rating Ive came up with on my 2004,4x4,2500lt crew cab w/6.6 in. bed (short box) is 9900lbs., if anyone knows of a more correct number please respond, thanks

Changing diff gears is not necessary for such a small difference in tire size. You would have to change front and rear gears to do it. Can't do just one.

If you're worried about speedo being slightly off, you can have that reprogrammed.

Stevens03 · May 27, 2009

No... You can't put different gear ratios in the front/rear diff. You can look in the glove box for the RPO code for what gears you have. GU6 = 3.42, GT4 = 3.73, and GT5 = 4.10

You can get a good increase in power by simply getting a custom tune, as much as 35hp. For towing power, gears would be your best choice. DO not put difference gear sets in front/rear diffs. If you want more power for towing, then drop to 4.56's and you'll have more than you need.

vertikal · May 27, 2009

No... You can't put different gear ratios in the front/rear diff. You can look in the glove box for the RPO code for what gears you have. GU6 = 3.42, GT4 = 3.73, and GT5 = 4.10

You can get a good increase in power by simply getting a custom tune, as much as 35hp. For towing power, gears would be your best choice. DO not put difference gear sets in front/rear diffs. If you want more power for towing, then drop to 4.56's and you'll have more than you need.

Thanks, this is a great site...people seem to be of great quality too.

vertikal · May 28, 2009

No... You can't put different gear ratios in the front/rear diff. You can look in the glove box for the RPO code for what gears you have. GU6 = 3.42, GT4 = 3.73, and GT5 = 4.10

You can get a good increase in power by simply getting a custom tune, as much as 35hp. For towing power, gears would be your best choice. DO not put difference gear sets in front/rear diffs. If you want more power for towing, then drop to 4.56's and you'll have more than you need.

Thanks, this is a great site...people seem to be of great quality too.

Ballpark the cost for 4.56 gears please...I'll call tommorow to see...but what would you think gears and labor would run?

Stevens03 · May 28, 2009

Every area seems to be a little different, but in my area a gear swap will cost you about $1200 for both front and rear. That includes labor, master rebuild kit and gears.

Worth every penny in my book if you've changed tire size or want more grunt.

vertikal · May 28, 2009

Every area seems to be a little different, but in my area a gear swap will cost you about $1200 for both front and rear. That includes labor, master rebuild kit and gears.

Worth every penny in my book if you've changed tire size or want more grunt.

it's a gt4 which is a 3.73....it towed ffithwheel well over Memorial day however I did notice it was straining upon acceleration at red lights and generally in traffic...did fine on interstate, I just hope since it is quadrasteer, they can insert 4.56 gears...may have to take to dealership where their knowledgable about these quad set ups(4 wheel steering), but I'd rather take it to this 4 wheel drive warehouse parts place down the road....with 4.56's it'll pull like a tractor huh? And gas wont last as long, well worst things have happened....just trying to pull this 9440 lb. camper(5th wheel) ugh!