Originally Posted by ckalogris
what setup do you currently run? will I be able to go on highway with 4.88, or I will see 3,000rpm at 60mph?
Why do you keep thinking the 4.88 rpms I recommend will be causing screaming high engine rpms?
I would not be repetitively recommending 4.88 to you if they would do that.
You would only be turning over 2400 rpms with your particular 4-speed automatic transmission at 70 mph with 33" tires and 4.88. Your 4-speed's overdrive has an extremely steep .69 overdrive ratio which is why I keep telling you that you need that 4.88 axle ratio to overcome it.
At 60 mph, as you asked about, you'd only be turning over 2057 rpms with 4.88.
One last comment that might help. After my '97 TJ was stolen, I bought my present '04 from a friend and it came with the same transmission you have, 35" tires, and 4.88 gearing. The engine lugs (rpms are too low) so I keep having to turn the overdrive off. With my 35" tires and 4-speed automatic, I'd be much happier with 5.13 or 5.38... 4.88 is not enough gear for 35" tires with this particular transmission. My present 4.88 would be ideal for 33" tires however. The previous owner admitted he screwed up by only installing 4.88 gearing with 35" tires, 5.13 or, and likely better, 5.38 would have been ideal.