I need some help,

I've been searching for some info on this and I can't find the answer that I need. I want to get my rear gears switched from 3.55 to 4.11s and I can'tfind info on the 2wd as faras changing the speedometer to match.

On the 4wd there's a gear in the transfer case that can be swapped, but obviouslythere's no transfer case on the 2wd.So the speedometer is getting it's speedfroma sensor in the transmission. But the tranny will be pushing a new gear in the rear and the speed won't match what the speedometer states, so how do you go about reprogramming it? I thought aboutusing a superchips but the website states it can't accomodate gear ratio changes in the Dodges. It will adjust for tire size though.

Stock for my truck was 245x75x16 tires with a rear diff of 3.55 at 70 MPH the RPM's should be 1889. To get close to that RPM at 70MPH with 4.11 gears could I just tell the programmer I have 35.5" tires which would net me 1879 RPMs? Is that a valid way to do it, or am I way overthinking this and there's a much easier way?

Thanks for any input!

 

The gear in the TC you were talking about is a 97 and down thing....the newer trucks get their speed off a tone ring on the carrier, so changing gears, provided you have not changed tire sizes, won't have changed the speedometer a bit. should you change the tires, you have to go to a dealer (at least that's the only places i've found around here that have the required programmer) and pay them a ridiculous amount of money for 5 mins of work. how do you like the TruTrack?

 

Love it! Compared to the crummy corporate trac-lok, it's unbelieveable. The trac-lok used to kind of sputter when it engaged, it would quickly catch, release,catch, releaseand the tires wouldchirp a bit, especially when it was wet outside. It eventually failed completely and bits of the clutch pack were lying in the bottom of my diff case when I changed the fluid in June. I did some research here and found it was a common problem and the factory unit was basically junk. Went with the Trutrac because it doesn't have any clutches to ever wear out, and Detriot Lockers are known for their durability.

I don't even notice the Trutrac is there. If it weren't for the fact thatI haven't ever peeled out regardless of road, gravel or dirt since I've had it, I'd think it wasn't working, but that's exactly waht it's supposed to do. I even pulled off the edge of the road onto the gravel side with half the truck on pavement and the other on gravel and floored it, and couldn't peelout. Plus you don't have to worry about whether or not you need a friction modifier in the gear oil, as there are no clutches, just gears.