mikmaze

there is another way to get back to stock effective power levels, lets say you do run that taller tire, & it changes your drive ratio by at most 25 %, add a Quad race box to the equation and end up with more torque than you started with !

Mcmopar

That might be right, but the added stresses on the driveline would be that much more. The gear change is the way to go.

cquestad

Somebody needs to check there math. NO Cummins needs gears that big. They are most happy IMHO between "net" 3.5 and 3.7.

I like my Tuff lift. There are mixed opinions about them, but in my experience...4-5 lifts on several brands of trucks, if you (or somebody) installs them correctly, align it correctly, use better shocks....you will be happy. I was happy with the OEM spring rates...so I did not see the need to buy another set of springs...yet.

I may choose to do that at some point, but at 90k...I still couldn't be more happy.

0425004x4

Cquestad, what gears do you have in your truck? I am thinking of puttin a 4.5 inch lift on my truck with some 37's do yours rub? How does it do towing? Thanks.

cquestad

I have 4:10's...

If my power is turned down...I still have no issues towing. With it turned up...I would not have any issues with any gears! (see sig).

Any ways...37's with a 4.5 inch lift great as long as you have a wheel with close to facotry specys...within 1" of width and .5" of backspacing. I have no rubbing anywhere...even twisted up on the trail. I would not run 37's with 3.73's.

rockittboy

i run 37's with 3.73s and up until this week have had no power mods. i got 18 hand calc on the freeway and about 14-15 in town. more than enough power to pull my car trailer with a 65 caddy down the freeway. HOWEVER...i know this is stressing my tranny more than necessary. currently i am looking at 4.10's OR 4.56's so i can run 40's with about the same mpg. if you CAN...4.10's are great for 37's and 3.73's will work just fine for 99% of the ppl out there. this is just my opinion after running the 37" and 3.73 combo for 30k.

0425004x4

Thanks for the replies. I really wish my truck came with 4.10's. That is the only thing I hate about it.

Mcmopar

Yea that's right , go put some 38's or bigger on a truck with 3.54's and hit it with say 400++HP and see what happens. You will be buying a transmission, possibly a X-fer case and a good chance some u-joints. When the tires get huge you need to change the gears or upgrade everthing in between!!

cquestad

I am not saying 3.53's....

But since you feel like arguing...lets!

I beg to differ...3.50's will put less stress on a u-joint and a tranny than 4.10's. Plus...3.50's are stronger than 4.10's at the same ring gear size because the small gear is larger!

I have 90k on 37's (70k above 500 hp, 15 k above 400 hp) to prove otherwise. 4.54 or higher would be a huge waste of RPM's, top end speed, and money with zero benifit.

My truck was faster in the 1/4 (all things kept equal) when I switched from 35's to 37's. Turbo felt load quicker...spooled sooner...etc. My experience only...

Run 35's if you have 3.73's, and 37's if you have 4.10's.

It sounds like you have limited experience...with maybe "under axle'd" 1/2 tons.



There are probably 10 members on this forum with 500 plus hp, lots of miles...and "net" gearing of 3:53 or so. Ask them?????

Mcmopar

That's all I have to say.

cquestad

Um...no.

Look at it the other wise. Fix the load and the rate of acceleration and the "required" horsepower is the same. The only varience is the RPM. So lower the RPM, and the torque required is increased. Raise the RPM and required torque is decreased. So I will have to agree with you that in that situation, the force on the driveline (up to the axle shafts...they would not feel the difference) is increased. It is a linear function...so the simple change in gearing would describe the increase or decrease of torque. 3.53 to 3.73 is about a 6% increase (or decrease in torque).

But that is unrealistic...the engines output is the engine's output...

With out changing the engines output, fix the load, fix the horsepower, and the rate of acceleration decreases, due to the loss of torque (less torque multiplication).

The concern is not gearing...period. We may have a maximum of 10-20% possible change in gearing to be able to keep the truck drivable (reasonable top speed...reasonable bottom end). That is a 10-20% of torque increase or decrease that the driveline sees. With a few bucks...the engine's output can be increased 30%-100% (120% in my case). I think I would be more concerned with the power added with regards to driveline stress that the effect that gearing has.

Real world experience is the bottom line...and the driveline in these trucks have proved time and time again to support big big hp for many many miles. If you are going to run a 400 hp truck...I would not be worried about whether you have 3.5's, 3.7's, or 4.1's.

Mountain's out of Mole hills here...


Oh...btw...so do you agree with me that a 3.73 gear set is stronger than a 4.10 at the same ring gear size?

Mcmopar

Yes, the gears themselves are stronger, in part due to the thickness.

adamkn

So it sounds like the difference in U-joint stress is negligible, whether higher or lower gears. You're either applying additional torque, or less torque (arguably) but additional RPMs - both equal more wear & tear.

What about transmission wear? Just like it's bad to "lug" an engine, isn't it also bad to "lug" a tranny? Correct me if I'm wrong, as I dont know trannys too well. But anyway, if your RPMs are lower, the tranny fluid pump (I'm assuming it's similar to engine pump) wont be moving as much fluid, and thus the internal transmission parts wont be lubed as well, allowing them to get hotter and wear faster. True or false?

Thanks for any input!

lightening ram

i agree i had 4.10 in my 05 truck and now i have 3.73 in 06 truck, my stock rpm was equal to the 4.10 with a 34" tire, also ran 35s with 4.10 was ok but liked the 33 with 4.10 for pulling thebest, a 37 with 4.10 might be ok when cruising but hook something to the hitch and you will need the od button off to get optimum power 21-2200 rpm i found the truck just cruises effortlessly no matter what load i have behind it. just my experience.

Mcmopar

I think the real issue here is that at lower RPM's you have less pressure to keep things "doing their job".