A while back my family and I took a trip over one of the local passes. On the way back we were following a JKU towing a day boat. As we went over the pass the JKU pretty much left me in the dust. My 2DR 3.6 w/ 4:10s (in 5th/6th gear) was incredibly hard-pressed to keep up with the 4DR JKU towing a boat. We were doing about 70MPH. This has been nagging me for some time. Is this because of my gears or the engine or both?

I don't have any plans to swap the gears out but am curious to know why this might be the case.

Thanks.

 

What was you tire size compared to theirs? Maybe he regeared or maybe had a supercharger or hemi upgrade. Hell, I sometimes have 18 wheelers pass me uphill lol.

 

All good info. Thanks.

I have 295s w/ stock rims on my rig. His looked pretty stock. The 295s did hit my acceleration a tad bit but not really that much.

I had thought that it could be due to the fact that the older 3.8s didn't have to rev as high to hit the HP peak but wasn't sure. If I dropped down to 4th gear and revved to 5k RPMs, I was able to gain pretty steadily but the gas mileage was dramatically impacted. As an example climbing one of the last passes, I stayed in 4th/5th to keep pace. My RPMs were between 4k-5K+. I was about 120 Mi into the trip and had an average of 17.2 MPG (via the in-dash computer) around the base of the pass. After climbing that single pass in the lower gears, my avg MPG dropped almost 4MPG to 14.5MPG. I just don't understand how the 120 Mi AVG can be impacted so dramatically over the course of, say, 5-7 Mi...

 

Had to have Hemi or LS-1 conversion.

 

^^ There is your answer. The guy in the JKU was likely doing 5k rpms in a lower gear. If he were in higher gear, he most likely wouldn't be able to maintain 70mph going up, or would severely strain his engine/tranny. If you don't want to run 5k rpm, then slow down over the pass. There is no other way around it. Also, this has little to do with gearing, but the actual rpm.