Ok, first of all I have a 1997 Ram 1500 Laramie with a 5.9l, auto, 4x4, 33x12.5R20. Recently my LSD finally took a **** after 23 years of faithful service. I needed the truck back up and running quickly so I found a reman axle with 3:55 gears. After installing the new rear axle I realized the speedo was off about 5mph at 60mph. This got me a little concerned because I know if the axle gearing was the same I wouldn't have any changes. So I ended up pulling apart the old rear-end and found that they were originally 3:90s.

What has me a little confused is that the truck seems to stay in overdrive more often now and feels better on hills then before. This is confusing because with the oversized tires the 3:90s SHOULD have felt better. Has anyone else come across this issue? Or is it all in my head?

Since this new rear axle is different, I am planning on rebuilding the old axle with 4:56 so I SHOULD be able to run the 35s better (after the 33s are shot). I'm just curious as to why the truck feels better with the 3:55 instead of the 3:90s? Any advice or comments would be appreciated.

Thanks in advance.

 

Probably because the old axle was going bad and caused drag or didn't hook up as well. I'd say if it feels better, have fun!

 

If you can fine a DRB3 and reset the pinion factor with the new gear ratio. I believe you will find it in the ABS module.

 

Simple. According to calculator, at 60 mph your engine revs roughly 150 rpm's lower. So you kind of have more reserve on powerband w/3.55 gears.

 

I will see how it feels with the new AirGap intake install. Maybe then the 3:90s will feel better since the new intake is suppose to raise the powerband up more.