3.73 to 4.10
 

In the near future I am planning on adding a 3" spindle lift with blocks in the back...I currently have 3.73...I have read that it is recommended to switch to 4.10 with 31" or bigger tires...is this true? And if I kept with the 3.73 what would happen? MPG go down? Huge powerloss??? Thanks

You speedo will be off more if you don't re-gear. MPG won't change much (if you compensate for the error in the odometer). You will have an apparent power loss.

I'm running 4.56 with my 35's -- I had 4.10 with my 31's.

You really wont notice much of a difference, only that your rpm's are higher on the highway.

If he keeps the 3.73 (as he is asking) and goes to 31's, his RPM's on the highway will go DOWN and he will have a noticeable powerloss on takeoff.

i have 3.73's and 31's and though i do fine on a flat freeway if i get on ANY type of slope or a wind my truck downshifts, doing about 65-70. i went from 19.5mpg to 16mpg and my speedo is off a ration of 15:1(at 60mph on the speedo i am actually doing 64)

I've got 32's and 4.10's. I have my speedo calibrated. and lost about 2-3 mpg.
I'm thinking of going with a 4.30 gear to get some of my low end back, and maybe I'll get some mpg back. I think 4.56 will be way to low. with the 4.30's my gearing should be back to about 3.80 with the 32's

so if i were to get 4.10, it would mean i would have to go to an 8.8 or is their something smaller? or is there some way to squeeze 4.10 into a 7.5? and if i were to switch would it be the whole axle or just the differential?

i am totally in the dark on this subject...

No you would put your 4.10 gears in your 7.5. No need for replacing the rear axle. here try this gears. Relatively easy install. plus its pretty cheap. might as well add a posi or ls while ur back there... jj.

yea was definitely goin to go with a LSD...need to get some money...so many mods I want to do...dont know where to start...
thanks for the link, that is awesome