I just finally got the 6in lift on and have 33's left over from my level kit.

I want to move on up to 36's or 37's and regear but 1 problem.... I run stock tires in the winter (because of salt) and am wondering if while i have the stock tires on if I will have an issue of going down the expressway at like 5 grand because its not pulling that "extra weight" (the tires) BTW thinking 4.88 since I pull things quite often

 

Not sure if it'll be at 5 grand but it will be turning more RPM's. Not so much because of the extra weight but because the smaller tire turns more than the bigger tires which will cause you to be running at a higher RPM.

 

stick with 35s for a 6". Anything more and they rub and just look out of proportion. 35s with 4.56s is my vote.

 

Here's the RPM's with the 37's at 2500 RPM's:


Here it is with stock tires at 3500 RPMs.


See, with the stock tires you'll be turning 1000 more RPM's to do the same speed.

 

it could be lower then that chart by about 300rpm. I dont think that chart factors in the torque converter locking.

 

Not sure if it does or not. At least it give ya an idea of what it'll be turning.

 

Don't forget we have od in our trucks so 456 is like 373 when in OD. 488 is like 390 when in od.

 

Im going to have to play the newb card here because im getting into things ive never delt with i played with that chart above on angelfire and after the comment "rus" said I figure 4.88 is good for me if what he is saying it true about it becoming a 3.90 in OD so im going to assume that when I do the rear diff I will have to do the 4WD diff also? And why is it that most people choose a 4.56 if they have 35's? i supose its personal preferance to a point but what about wear and tear? is what im looking at

 

Yes , need to do front diff also. 4.56 gives enough grunt with 5.4 up to 35's as most trucks come with either 3.55 or 3.73s. Wear and tear not higher for me as many times I was always driving with od off with my 373's. I also have an FTVB in my tranny.

Rus

 

To determine rpm at any speed, look at rpm at speed now. If you change gears. multiply current rpm by new ratio divided by old ratio.

for example, if your truck now turns 2150rpm at 80 with 3.55 gears, multiply rpm by 4.88 and divide by 3.55 to determine rpm with 4.88 gears.
Same thing with tires. Multiply present rpm by new tire diameter and divide by old tire diameter. simple

 

Well I have a 4.6 with that being said do you think i should step up a little extra to the 4.88?

 

Here is an awesome gear ratio calculator. I have uesd it on all my gear cahnges and it is spot on.

http://www.f-body.org/gears/