Join Date: May 2000
Location: Raleigh, NC
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cruising rpm and gearing
I'm in the middle of a frame-up rebuild on my '76 CJ-7. It has the 258, and a TH400 slushbox with the quadratrac system. I was surprised to find that according the letter code (L) on the rear axle, the axles are geared at 4.10. This seems a bit high for the TH400 with stock P235 tires. Supposedly this Jeep was used on a farm, so it probably never saw the highway.
I'm considering going to college 5+ hours away in the mountains, so highway speed will be important to me. On my '83 CJ-7 that I drive everyday, my cruising rpm is about 2100 at 65mph. With these 4.10 gears, the '76 CJ-7 would have to be running around 3100 RPM to hold 65 with 30" stockish tires. I would like to go to 33"s, which would bring the RPMs down to about 2700.
What RPM is everyone running their inline 6 at on the highway? what is the ideal RPM for highway cruising?
any input would be appreciated! thanks
83 CJ-7 and 76 CJ-7 with stuff