My 78 258/3spd hits 55mph around 2200rpm. 65 is up around 2800-3k..

It all depends on the axle gearing. I have no idea what I have in mine- been too lazy to climb under and look..

 

Top speed depends on three things outside of wind resistance and road grade.....engine RPM , transmission gear (if 1 to 1 or overdrive) axle gearing and tire size. These all combine to give you the results. IF engine RPM is a constant AND the transmissions top gear is a 1 to 1 like in a 3 or 4 speed unit, the deciding factors are your tire size and axle gearing. Due to the wide range of each, CJs are very different in how they feel with gearing. My 75 has 3.73 gears and 29 inch tires....first is only used from a dead stop....any foward rolling, its second and third up to about 65 MPH...thats really it. My 83 has 2.27 gears and with the same tires, its a pig to drive, but goes faster top end. The best combo for a DD for me, had been my 86 with 3.31 gears, same tires, and overdrive 5 speed. Goo pickup, top end of about 85 to 90mph...

 

My CJ5 with a 3spd, 5.38s, on 33 inch tires turns about 3000rpm at 50mph.

 

4 speed will not increase your top speed since the gears are the same in 3rd on the 3 speed and 4th on the 4 speed. Probably obvious but make sure you are not in 4 low. 3 speeds are fairly wide ratio trannys and you shouldn't really be rowing through the gears all that fast.

 

I'm running 3.54 axle gearing, T150 tranny, 33x12.50in tires and I average around 2200-2300 at 55mph. I've had mine up to 75 on the interstate before, running that fast for about 3 hrs.

 

You need a 5 speed or modded T85 (I think that's the number. It's a T15 with reverse replaced with an O/D and reverse moved to the tailstock) to get higher speed. I don't know if there is a 4x4 version, but I had one in my Ford pickup and installed one in my '66 Fairlane.

 

My 75 has 3:73 gears and I typically don't go over 45/50 mph. But I've had it up to about 55/60 mph for about 45 minutes straight with no problems.

 

I'm with Cherokeester, make sure you aren't in 4LO, or the mysterious 2LO position. I also have the T150, and that sounds like exactly what mine would be like in LO.

 

I have a 79 CJ7 with the t150, stock gearing and 31" tall tires, I can do 55-60 no problem, you might mistake being in 4 lo as steering problems, as it will bind up and do all kinds of weird things while trying to turn, also the 2 lo issue is very likely, I'm with anyone who has mentioned this as being the most likely cause. Good Luck!

 

79 with a T150, 3.73 gears, 33" swampers.

Ran it for the 1st time at speed yesterday, 55mpg, turning right about 2100 rpm. If I can do 60 or 65 as smooth as it did yesterday, I will be super stoked.

 

I'd make sure you aren't in 4 lo. That could cause the steering issues and the winding out at 45.