ShutterBug

I recently swapped my 3.21 open diff housings with a set of Rubicon housings that were geared to 4.88. I have a 3.6l automatic transmission. I've used an AEV Procal to "reprogram" the Jeep for the final drive ratio - the speedometer tracks perfectly.

HOWEVER - it just feels weird at slow speeds. I can feel the transmission downshift when slowing to a stop. Sometimes, it's not very smooth, at least not what I am used to.

Is this normal? What should I have expected? I'd like to hear from others that have made this jump.

ronjenx

Lower gears will accentuate the downshift. That is normal. Engine braking is more effective.
Try it in 4lo and you will find it much more noticeable.
It's just like pressing and releasing the gas pedal in 4th gear, then trying it in 1st gear.

Canvas

I went from 3.73 to 5.13 and it was like my Jeep was a race car. Then again I have a 6sp.

Drive it a while and you will get used to it.

BrowniesJK

That's very normal. Not sure what the AEV programmer does but my super chips corrects shift points as well. Helped out a lot with this same issue.

mhockey9090

Normal for me as well.

ShutterBug

I'm not exactly sure what the ProCal does outside of just recalibrating the speedometer. I understand that the shift points are all triggered by speed and RPM.

The gears have been in for about a month or so and I still haven't gotten used to it. It feels like something is wrong.

AirJordan613

I'm sure it's just a matter of getting used to. I went from 3.73 to 4.88 as well. I have the 4-speed auto though. Perhaps you're feeling more downshifts because you're actually getting up into higher gears at a given speed. I think you're biggest issue now is just learning to enjoy the newly found power!

ShutterBug

Went out for a few hours at a local OHV park. Lockers and gears make such a difference. Many things were effortless. Other things were just more fun!

I'm heading to the Tennessee Mountain Jeep Jamboree in a couple weeks. This will be the first REAL test of the axle swap, plus the 8 hour drive will give me a good idea of real gas mileage now. It looks to be averaging between 14 and 15.

After that, I'll be hitting Rausch Creek in May for the JK Freak Fest.

I hope y'all are right about this. It still feels really weird. I may reset the ProCal back to stock and see if that makes any difference at all.