Fellow truckers, I have a problem that I need help with. I have a 06 GMC 3500 diesel 4x4 crew cab LB with a 7"lift 36" tires. Running 3.73 stock gears. I have only a hypertech programmer as a mod. The truck does fine. The thing is that I am getting a 26 ft. toy hauler this week end. Fully loaded it will weigh around 10,000 lbs. Should I leave the gears stock and down size to a 35" tire or gear 4.10 or even 4.56? Anyone have delt with this issue?

Is it bumper hitch or fifth wheel? If it's fifth wheel you might have trouble pulling it with the lift and tires.

I wouldn't regear for 35's. If it was a 2 wheel drive I might consider it but too expensive on a 4x4. You can always drop it down a gear if needed but I think you will find it will pull just fine.

I tow 10,000lbs+ with 35.5" tires and I would never consider regearing. If anything I would like to see it geared a bit higher especially unloaded.

Just my opinion ;)

its a bumper tow hitch. As of now running down the highway at 75 mph my rpm is 12-1400. That is with 6 th gear engaged. I wonder if I can just put in manual mode and run 4th and 5 th gear.

Specifically what size and kind of tires do you have?

In my opinion you need a exhaust system with a programmer,big tires,stock gears,and towing that kind of a load.but, thats just my opinion.i would have a 4" exhaust with at least a free flow muffler on it before i ever pulled that kind of a load with your combo just from a EGT standpoint alone.

You will not "need" to re-gear. the truck will pull it just fine.however if you were to re-gear to 4.10's it would pull it that much better. 4.56's would be way too much. try it with the stock gears.

with a stock truck i dont think it is safe to pull that kind of weight in 6th gear but im sure the LBZ/6 speed guys will chime in who know more about that than i do.i have the lowly 5 speed

Stock gears will be fine for that weight and tire size. If you go to 37's I would regear to 4.11's for your weight.

I didn't change to 4.11's till I got the 16,000pd 5er. I tow in 5th (od) always, the truck normally doesn't come out of OD unless the hill is large. If I didn't have the heavy trailer I would have stock gears.

I tried 4.56's and it was way to high, the truck would never shift out of OD even on large hills and if I slowed down and got it to shift to 4th before the hill it would hit 3200rpm's and speed topped at about 50 or so, so it was miserable.

Specifically what size and kind of tires do you have?

In my opinion you need a exhaust system with a programmer,big tires,stock gears,and towing that kind of a load.but, thats just my opinion.i would have a 4" exhaust with at least a free flow muffler on it before i ever pulled that kind of a load with your combo just from a EGT standpoint alone.

You will not "need" to re-gear. the truck will pull it just fine.however if you were to re-gear to 4.10's it would pull it that much better. 4.56's would be way too much. try it with the stock gears.

with a stock truck i dont think it is safe to pull that kind of weight in 6th gear but im sure the LBZ/6 speed guys will chime in who know more about that than i do.i have the lowly 5 speed
B rad i am running 36x14.50 Parnelli Jones Dirt Grips E rated on a 16x10 pro comp wheel. This is why I thought I could down grade to 315/75/r16 if the tires were to much. I am running a Cognito lift set at 7" so the tires will not look bad. As for exhausts, there is a ton of choices. I wanted the AEM oil free in take with a BRP exhaust. Any recommendations? I thought since GM offers a 4.10 option I could have them put them in. This way I do not void warranty. What do you think?

you will not see enough of a difference with the 315's from what you have. plus it will not look as good :)

exhaust: mbrp, magnaflow are good choices.never heard of BRP, maybe you mean RBP which is rolling big power. i have a no name brand 5" that i got off of ebay for $270.00 and its awesome.

if you re-gear to 4.10 you will not be disappointed.thats about a 11% increase and it will make a huge difference.you just have to do both front and rear. it was not a question for me when i did the lift. i re-geared

RBP that's what I meant. Brain Fart! I just do not know about diesel exhausts. This is my first oil burner. I have seen so many advertized. What about the AEM oil less intake? What about banks complete exhaust/intake? As for the gearing What about having GM do it? any help is much appreciated. Your truck looks pretty stout by the way. I like red. Mine is black but I would have gotten red in a minute.

Well RadVans I guess all I can do is try it? I will have to get an exhaust. I guess I will take a trip to Glammis and find out! I was thinking of going to 37's after these tires wear out. The 14.50 with is to much. They rub. I guess I will do 4.11 before the tire change. Thanks man!

if you look in my garage the pic of me hauling hay is with 35" and the stock gears it will pull just fine i wouldn't put your money into gears till you get the taller tires and i was able to keep up with the guy that was helping me he was only pulling a 16ft flat bed so the stock gears are still fine with 35" tires

thanks :ro) you need to post up some pics of your rig.

honestly on intakes they are a waste of money unless you want more turbo whistle. there has been much discussion/dyno numbers/etc. about this. some will actually lose power. just drill some holes in the bottom of your stock air box just beneath the filter and you can take it another step further and cut holes in the bottom plate under your airbox like i did.i just notched a square with the dremel under where i drilled holes.and get a good hi flow filter. i have a k&n and some dont like those. amsoil and a few others make good replacement filters and you'll save some money and have better than cold air or aftermarket intake you can buy

as far as who does the gears is up to you. im sure there are many qualified gm mechanics that can do it. i do all my own stuff so i really cant help you there.

the banks exhaust is the quietest i have ever heard. so if that is your thing i would recommend it. if you want some "racket" try something else such as what i listed in above posts

Thanks for the info. As for the pics I have tried but the computer says the pics resolution is to big. I will try again.

I ran 37's (355/60R20) on my 03' Dmax and loved the empty cruising RPM's, but as soon as I hooked up to my 28' Toyhauler (bumper pull) I wished I had done the gears. The truck pulled the trailer fine, but would lug alot or I would have to pull in 4th all the time, got poor MPG's, EGT's were higher than I would have liked and the trans would get hot. Then I got my 06' and pulled the trailer with it stock and loved all the extra power it had and made me never want to pull the hauler with the 03' again. Doing gears would definitely help your situation, and I would do them if I were to ever lift another truck again. It just sucks it cost's so much to get them done

I run 4.10's,NOT worth the extra $$$.A Box or Programmer will more than make up for it.Does help crawling around in the mountains though.

I put 4.10 in and it helped a lot, with 33 inch tires the spedo is 3% fast. With your 35" tires it should be about right. Paid 2300 for both axels using factory parts. I tow a 15000 pound fifth and it made all the difference in the world.

I would put in 4.10's or 4.56's for those tires. Less strain on the trans and u-joints when towing and when empty. You may find its a fuel guzzler compared to stock because it is working so much harder turning those tires when loaded.

35 inch tires and 4.10 is very close to the same as 31 inch tires and 3.73. There is a reason the Duramax is only offered with 3.73 gears, and that is because it is the best choice for multiple uses. Adding 4.10's will make your truck perform like it did stock. Stay away from 4.56's too low.:cool:

Well everyone I hauled the toyhauler and the truck did fine. From Vegas to Dumont. There is a few steep climbs. 4,000 ft The tire pressure set at 60 psi It climbed fine. I had to check myself cause it wanted to hit 70 mph quick! the tranny never got near hot, the temp of the truck was never over 210. I figure with the exaust changed and maybe a cold air intake. We will be fine. The Allison spent it's time between 4th and 5th. gear. 1,900-2,000 rpm. So I guess 3.73 gears and 36" tires are not to bad. Thanks for all the advice everyone, truck on!!!!!!!!