Chaging rear end on gen 4 2015 ram 5.7 8 speed auto tranns from 321 to 355 or 392

[bfry10]

I would like to know the what must be done electronically to change rear end/ differential from 3:21 to 3:55 ,3:92

 

[chopperman1]

Absolutely nothing. If it's a 4x4 you need to change front diff too. They need to match.

 

[crash68]

^^^ what he said
Vehicle speed is determined from the ABS speed sensors at each wheel so the speedometer isn't effected by a gear ratio change

 

[danielmid]

While that's true for vehicle speed, I would still jump in to Alfa and change the ratio there. I remember reading a post here about the transmission being lost after a gear change that was fixed by the Alfa update, I'll see if I can find it.

 

[GTyankee]

LOL
just change to 3.92 ratio
change to a throttle commander
change your tighty whities

then all that is left is some LSD, oops limit slip differential

 

[Wild one]

LOL
just change to 3.92 ratio
change to a throttle commander
change your tighty whities

then all that is left is some LSD, oops limit slip differential

3.55's are easier to find and usually alot cheaper then 3.92's,and are a good middle of the road gear set between 3.21's and 3.92's.They create less oil temp ,get better gas milege then 3.92's will,and if you tune the truck and open up the limiter are noticably faster wide open,and not a hell'va lot slower on a light to light race

 

[co-pilot]

3.21 to 3.55 is not worth the money ....{ in my opinion}.....tire size comes in on this also.....

 

[Daw14]

No changes needed when going to a different ratio , it’s been 3 years since I swapped gears and all is still good.