regearing

josue · July 25, 2004

I just had my 03 2500hd lifted and put 315/75/16 BFGS A/T. Do I need to regear the rear, and if so to what. If I go with 4.56 will that be enough for the tires and tow my future 29ft toy box.

Shaners · July 26, 2004

We have a guy here that has done just what you need. He goes by "shotgun" . He just put 4.56's in his 1500 HD and loves it. He tows a travel trailer so he needed a little extra gear to go with his big tires.

JimWilson · July 26, 2004

What gears are you running now? If it's 4.10's, then maybe not. But if it's 3.73's then I think it would be a good idea. 315's (35's) aren't all that big, but a 29 foot trailer -- especially a toy hauler -- can get a bit heavy once you load all your stuff in it.

Mort · July 26, 2004

You have gone up roughly 14% in tire diameter. Therefore to maintain the towing capacity that your truck came with you will want to go up a similar amount in gears numerically. This will also help to reduce transmission and driveline loads required to turn those heavier and bigger tires.

My guess is that you have 4.10s now so an increase of 14% would add 0.574 to equal 4.67s . So yes 4.56 would be a good choice. If you load that trailer up close to your truck's towing capacity then you might even want to consider 4.88s. That choice will partially depend on your engine and transmission. The 4.88s would be a good selection to go with the 6000 Vortec and 4L80-E. If you have the 3.73 gears then a 14% increase is 0.522 to equal 4.25. So the 4.56 is still a good choice and it will give you a little extra to boot.

jelisfc · July 26, 2004

What engine do you have? A 6.0 I'd agree with the others. It sounds like 4.56's are the way to go. 8.1/3.73 if you're going to change might at well go all the way to 4.56. 8.1/4.10 try it and see how she pulls. Dmax/3.73 spend your money on a tuner.

I've got a Dmax/6 spd stock and it pulls my enclosed sled trailer (5K) fine in MN. Fine to me means it can get the job done but if your trailer is closer to 10K or you pull it all over the country you'll want to do something.

whitesnake01 · July 26, 2004

What gears are you running now? If it's 4.10's, then maybe not. But if it's 3.73's then I think it would be a good idea.

I do not think it matters what gear you started with. If you increase the diameter by 14%, it needs 14% more gears to drive in a similar manner. Sure, if you started with 4.10s, you'r truck could probably "handle it", but it'll still be like you lost power. And you will feel that when you tow, for sure. Regearing gives you back what the bigger diameter tires took away. Overgearing a little bit might not be a bad idea if you drive through mountains alot with your trailer. Undergearing in the same environment is not a good idea.

Shotgun · July 27, 2004

I just had my 03 2500hd lifted and put 315/75/16 BFGS A/T. Do I need to regear the rear, and if so to what. If I go with 4.56 will that be enough for the tires and tow my future 29ft toy box.

Your tires are 34.6"" tall so I would say yes,4.56's should be right in the wheel house.I am running 33" tires with the 4.56's and they are just about right. The change will amaze you and you will realize how much giddy up you lost with the big meats.

JimWilson · July 27, 2004

I do not think it matters what gear you started with. If you increase the diameter by 14%, it needs 14% more gears to drive in a similar manner. Sure, if you started with 4.10s, you'r truck could probably "handle it", but it'll still be like you lost power.

That's precisely why I included the caveat in my original post.

With 4.10's it would be more of a desirable thing to do, but with 3.73's it most likely be a necessity. There's a difference between the two, and since it's probably going to cost north of $1000 to get a 4x4 done that difference might be enough to make someone think twice about spending that amount of money.

I'm a big proponent of "try first, spend second". Well, at least my financial position (and wife!) dictate that anyway...

GlennRMK · July 27, 2004

What engine and tranny?

If you already have 4.10s with an 8.1, I wouldn't regear. But, if you have 3.73s, I would go to 4.56s.

If you have a diesel I would not regear.

If you have the 6.0, I would go to 4.56s for sure. You might get by with 4.10s, but the 4.56s would be nice.

If you have an auto, that is even more reason to upgrade, IMO.

tbyrne · July 27, 2004

I recently went from 4.10 to 4.56 gears in my HD. This was after bolting on a set of 37" tires. I would say that it was a night and day difference with the Allison at 65MPH but overall accelleration improved. I wanted to go with a set of 4.88 gears but there we no fronts avalable anywhere. The front 4.56s were also a project to locate.

2002 8.1 Silverado HD - Full Throttle lift, 37" tires, 4.56 gears, Comp Cam, TOG headers, Volant induction plus more! Whipple supercharger coming soon!

2002 8.1 Suburban -Intercooled Whipple supercharger, 22" wheels/tires + more - 407hp/558 ft-lb torque at the rear wheels - 13.93 @ 95.79 MPH

www.tbyrnemotorsports.com