Well why do they? Is it due to the turbo needing something to push against with all the boost?

Thanks!

 

You dont need a low ratio due to all the torque available and low first gear in the Ally. But if you want to, gears are now ready to install for the 11.5 rear. Took them over a year to make them, but, better late than never. Up to 4.56's. Can you imagine the low end with 4.56 rear and the torque of the D-max? WOW!!!!

 

Well I figure if I tossed on some larger tires instead of those tiny weight rated ones, I would hurt the fuel economy as well as performance...sorta like what happened to your truck BADHD. Speaking of which have you tried running down the freeway at 60MPH in D? That may help out your fuel economy until you decide on gears/converter.

The stock tire height is ~30.5" and I would probably go to around a 33" tire so the truck looks normal. That would put me needing about a 4.10:1 gear set, BUT I really would like to go to a 4.30:1 gear set but it seems no one makes that low of a gear.

Here is what I came up with...

3.73:1 + 30.5" tires @ 70mph = ~2025rpms
3.73:1 + 33" tires @ 70mph = ~1850rpms
4.10:1 + 33" tires @ 70mph = ~2050rpms
4.30:1 + 33" tires @ 70mph = ~2150rpms
4.56:1 + 35" tires @ 70mph = ~2150rpms

Can 35" tires be on a stock ride height? Is an Eaton Posi avaiable for that gigantic 11.5"?

 

They only offer 3.73's because GM is afraid they would lose Kodiak/Topkick sales if 4.10 or 4.56 gears were available.

 

I have 33s on my Dmax and have 0 problems with bottom end torque.I would'nt even consider a swap unless going bigger than 35s.You cant compare a 6.0 to the torque of a Dmax.A gear deeper than a 3.73 is unnecessary with an Ally Dmax combo.I've pulled 23,000 lbs with my truck no problems whatsoever with acceleration.A 4.10-4.56 would be more gear than the brakes and suspension could ever stop or hold(towing wise).See sig for performance in the 1320 with 33s spinning half way down the track.

 

Yeah, but did your fuel economy decrease with the larger tires?

 

Yes fuel economy did drop about 1-1.5 mpg.IMHO if someone didnt like the very small decrease in performance JUICE IT.Upping the power is alot cheaper and more fun than a gear swap,especially with a 4x4.The small decrease in economy is well worth it for the look,those little donuts Chevy puts on these trucks look goofy.

 

Well yeah, but seeing as how I would stick an Eaton E-Locker up front and a REAL limited slip out back, a few $100's more for the gears wouldn't be too bad.

Oh yeah, those 245/75R16 are weight rated hence them being on those trucks. I'd never tow anything that would need that sort of tire so, I would off them too. Probably a 305/70R16 or something comparable.