To be a bit more accurate, the NVG3550 has a 0.78 ratio for 5th and most
brands of 33" tires are actually around 32.8" when new. So, with a 4.56
diff, Troy's I6 would be turning 2550 rpm at 70 mph. Right now, with his
4.11 diff, it should turn 2300 rpm @ 70 mph. If he up-sizes to 35s,
he'll turn 2400 with 4.56 or 2570 with 4.88 (70 mph).

Steve
http://xjeep.dyndns.org

c wrote:
> "Troy" > wrote :
>
>>I have an 01 jeep tj 6 cyl. 5spd manual
>
> RPM = gear ratio x mph x 336 / tire diameter.
>
> So in your case 3250 RPM without overdrive and then multiply that by the
> overdrive ratio of the trans. It is usually about .7, so you should be about
> 2275 RPM
>
> Chris