2800 RPM at 75 mph.

 

Mileage must suck

 

Definitely 5.13 on the auto trans.

 

We run 2600rpm @ 70. Mileage on the highway is about the same as stock. Wife driving to work everyday mileage has decreased about 1mpg.
I didn't like the gearing stock, now it is acceptable.

 

Actually, gas mileage went UP two mpg from what it had been with 4.10 gears. Typical gas mileage was about 16.5 mpg.

 

Must be running 5.13's?

 

So I have one guy running 2800 rpm @ 75 mph with 5.38's and another running 2600 rpm @ 70 mph presumably with 5.13's. Now I'm really confused

Probably go with 5.13's, but now I have to consider 5.38's while at the same time not ruling out 4.88's.

 

Ours is 5.38 with 315/70-17 Duratracs. Still have to turn off OD to come up the hills from San Diego, but it's way better than stock. With stock Rubicon tires and 4.10s, it would somtimes go down to 2nd to get up the same hills.
One reason we went with 5.38 is my wife previously worked in Yellowstone, and wants to move back there when the kids are grown, already geared for it.

 

Nice. I'm real close to Yellowstone and Glacier here in Montana. That would be a great top off drive. I'm convinced it will either be 5.13 or 5.38. I don't think 4.88 will yield enough of a noticeable change to justify the expense of a gear change. Besides, 2600 rpm @ 70 isn't too bad.

Thanks for the info, I appreciate the insight.

 

There is only a hundred RPM difference at highway speed between 4.88 and 5.13, and another hundred RPM diffference between 5.13 and 5.38 gears. Its not like there is that big of a difference.

2600 RPM at 70 mph with 5.13s: Add a hundred RPM for the extra 5 mph, then add another 100 RPM for the 5.38 gears, and your looking at 2800 RPM at 75 mph.