3.73 To 4.10 Changes For An 08 2500hd 6.0 4x4

trucksnharleys · March 16, 2010

I have an '08 2500HD 4x4 with a stock 3.73 rear end in it and the standard 6.0. It's a crew cab and is only rated for 9800lbs towing. I'm looking at towing an 11K+ 5th wheel with it and was considering changing the rear end from 3.73 to 4.10. Per the owners manual, that puts me at 12K+ for towing capacity. Besides gears in the differential, I'm wondering what programming would be needed (speedo, shift points, etc.) and if I could accomodate that with an after-market computer add-on? I'm also wondering if anything has to be done mechanically because it's 4x4? Any thoughts besides "buy another truck" or "buy a smaller toy hauler" would be greatly appreciated! ;-)

plowking · March 17, 2010

One thing that I can think of is will this void your warranty? Is rear end only thing you need to change to get heavier gvw? Are tires rated for 12000 gvw? plowking

Stevens03 · March 17, 2010

Diablo could handle the gear update, and the 4.10's would make it a beast coupled with the 6-speed.

vettelovralexand · March 17, 2010

You would not only need to change your rear gear but also your front or else your drivetrain would bind while in 4wd. But electronically any number of companies have handheld programmers that would allow you to tune for the gear swap, but I would think that if you would be down for a few days to do the gear swap it would be an excellent time to send your stock ECM to be tuned by one of the custom tuners.

davzog · March 17, 2010

Yep, you need to change BOTH gear sets or everything will bind in 4 wheel drive.....I was going to do the exact same thing on an 03 Ram....they wanted $1200 for each gear set, so $2400 plus a programmer or custom tune to reset the speedometer, ABS, etc...another $300 or so.

I decided to go for a new truck to get what I needed....wanted an HD anyway....ha.

brims · March 17, 2010

Diablo could handle the gear update, and the 4.10's would make it a beast coupled with the 6-speed.

Don't lie to the man, the Diablo can't program the 4 speed trannys let alone the 6 speed, so you can change the engine parameters but you will be stuck with stock transmission programming.

rodram · March 18, 2010

just changing the gear ratio ..... (yes, you have to change BOTH front and rear in a 4x4) will not necessarily get you that towing capacity increase from 9800 to 12,000... or whatever..

.. and the so-called 'tow capacity' is a number set by the manufacturer (ie., GM) on the basis of many things including gear ratio, as well as the toughness and cooling capacity of your transmission, your engine power and cooling capacity, your springs, your tires, your axle differentials, and your brakes.... the limitations set by GM at 9800 lbs for whatever consideration could have been based on some limiting factor other than the 3.73 gear ratio....

.... I would check to make sure you have that Max Towing Capacity correct... the 9800 lbs seems low for a 2500HD, everyone I know has a 13,000 lb tow capacity in their 2500HD...

focijoe · March 18, 2010

just changing the gear ratio ..... (yes, you have to change BOTH front and rear in a 4x4) will not necessarily get you that towing capacity increase from 9800 to 12,000... or whatever..

.. and the so-called 'tow capacity' is a number set by the manufacturer (ie., GM) on the basis of many things including gear ratio, as well as the toughness and cooling capacity of your transmission, your engine power and cooling capacity, your springs, your tires, your axle differentials, and your brakes.... the limitations set by GM at 9800 lbs for whatever consideration could have been based on some limiting factor other than the 3.73 gear ratio....

.... I would check to make sure you have that Max Towing Capacity correct... the 9800 lbs seems low for a 2500HD, everyone I know has a 13,000 lb tow capacity in their 2500HD...

I have a '09 2500HD with the 3.73's and my max trailer weight is 9,900 lbs according to the manual. The same truck with 4.10's is rated at 12,400 in the manual. So going by the manual its just the gear ratio that gives you the extra towing capacity.

700 sportsman · March 19, 2010

Along with gears I would add air bags, and an larger trans. cooler

txdutt · March 19, 2010

only difference is the gear ratio-just about any programmer out there can reprogram the PCM for the change--but yeah your warranty goes poof!!

markw8 · March 19, 2010

The dealer could do the whole job and the warrenty would be good. It will cost more upfront, but might be cheaper down the road.

Mark.

trucksnharleys · March 19, 2010

The dealer could do the whole job and the warrenty would be good. It will cost more upfront, but might be cheaper down the road.

Mark.

I'm on my second dealer now. The first said "forget it" and the second said $4200 a quote. Both said that they've never heard of it being done before and neither wanted to touch it. The transmission shop I talked to said they'd do it for roughly $1500, but said they didn't touch ECMs. Didn't see on diablo site where their two systems could change shift points. Would have to ask the blackbear folks. My biggest worry is missing some setting and not being able to get it fixed. Wish there was someone who sold an "ECM browser" with latest description of the different bits/bytes. At least then I could play with it a bit. I'm feeling like this is a lost cause. It's hard to believe that given the simplicity of the computer and the availability of parts that this can't be done...Thanks for all the input so far.

Z'06 · March 19, 2010

Warranty, schmarranty. It never ceases to amaze me how many sheeple there are, particularly as a result of uninformed dealer service reps.

A simple gear change is NOT going to cause any problems that could void the warranty under the Magnuson-Moss Act (except the gears themselves and their installation, obviously), especially in the OP's 14-bolt, LOL. Besides, a lower gear ratio (higher numerical value) puts less stress on the transmission and engine under acceleration, so like the Vette servo, you are doing the warranty company a favor by prolonging the life of various components of your vehicle.

And yes, regearing requires a computer recalibration, which the dealers are fond of saying they can no longer do for us, so now you have an excuse to tell any dealer not to touch your PCM (for fear of reflashing it) because they would be on the hook for paying to have it RE-recalibrated.

brainpause · March 20, 2010

Small hijack here, but is relevant.

I talked to a guy today about changing my 3.42's to 4.10's. I am running stock size 265 tires.

He recommended I go to 4.56's and run 285's. I asked him why. He said "It's just a better setup." Couldn't give me rationale.

It was a primarily offroading shop, so maybe that was why.

Any thoughts?

Larry

Z'06 · March 20, 2010

Small hijack here, but is relevant.

I talked to a guy today about changing my 3.42's to 4.10's. I am running stock size 265 tires.

He recommended I go to 4.56's and run 285's. I asked him why. He said "It's just a better setup." Couldn't give me rationale.

It was a primarily offroading shop, so maybe that was why.

Any thoughts?

Larry

Very "torquey" setup on 285s. Popular combination (33" & 4.56) on FullSizeChevy.com. Good in-town MPG, but not so great on the highway because of high RPMs, but it's not the end of the world because LS engines like to rev.