3.21 to 3.9x cost

[Hoythews71]

Have a ‘19 Laramie Sport and want to lift with 35’s. Also don’t want to completely destroy gas mileage...

Would like 4.11’s, but can’t seem to find them online front and rear. Anyone made the switch to Mopar 3.92? Is the MPG difference noticeable for a mostly highway driver? And what did it cost to make the switch front and rear?

Thanks in advance!


Sent from my iPhone using Tapatalk

 

[clazer]

If you are mostly highway, you definitely do not want 4.11s- 3.92s will already be making your engine turn ~10% faster for the same speed after going to 35s.
This question pops up occasionally and I think the answer is normally that the front gears are hard to find. Hopefully that has changed.
Yes you are going to see a significant drop in mpg when lifting, bigger (probably wider too) tires, and making your engine run at higher rpm.

That all being said, do it. It’s fun. I’d recommend the lift and tires first, then evaluate if you want to start messing with the gears.

 

[Firebird]

It is my understanding that the front gears are welded in and cannot be changed. You would have to acquire a complete front end from a donor truck

 

[Rob5589]

Expect labor to be 400-800 per diff, plus parts. The rear (9.25) has been around a long time so sourcing parts is easy. According to the shop I was associated with, the front is something all new. They hadn't seen one when I spoke to them so they had no idea what it is.