Stay at 87 octane. While in altitude stay with an 85 octane. This lower octane is due to less oxygen, less air density, less burning and lower compression. We have become friend of one of the Jeep Ohio Plant guys due to my profession. He pointed out that the tranny on the Jeep 4.0L has some setbacks.
Second gear slips or bucks due to an internal transmission solenoid problem.
The new one holds up well. My shifts are up there high. One thing we d recommend is a external transmission cooler and a gauge giving you accurate temps. We re in the process of performing an install on ours as we type. Any help would be appreciated.