3 spd tranys

3 spd tranys

Jack Tupp

Northern California
I've been looking at getting a jeep and their a lot of three speed tranies out there. What's the top end limitations of those. I want to be able to drive it on the roads and highways. Getting to and from off road locations. Will it cruise at 55 or will it be winding out.
my dads has a 3 speed and it runs down the highway just fine. my has a 4 speed and its not any different for rpm vs cruising speed. it all depends on the gear ratio in the differentials. ours are 3.54. dads is a 258 inline 6 and mine is the 4cyl iron duke.
cass has it right. Top gear for any 3 speed is the same as any 4 speed. They are all 1 to 1 in top gear. The only overdrive to go into a CJ has been the T5 and you would want to avoid that POS tranny.
As Cass said the gearing in the axle and the tire size will dictate how it drives on the highway (RPMs).
The big difference in driving a 3 speed is their is a bigger separation between each gear. In other words if you are on the highway and want to downshift to pass someone and you have a 3 speed then when you downshift your engine will SCREAM! You really won't be able to downshift a 3 speed on the highway. You could redline.
In the '70s a lot of CJs came with very strong transmissions but they were often 3 speeds.
In the '80s a lot of CJs came with 4 or 5 speeds but they were often very weak transmissions.

All in all I would prefer a strong tranny from the '70s over what they had in the '80s.
The best transmission to go into a CJ is the T18.
When shopping for a CJ ask what tranny it has then check out this link to see if it is any good: http://www.jeep-cj.com/forums/f105/manual-cj-transmissions-12112/
As the others have stated the top gear in a Jeep 3 speed or 4 speed is 1:1 regardless of flavor and the main factor becomes the gearing in the axles. My stock 1972 CJ5 with an AMC 304, 3 speed T-15 transmission, and what I suspect were 3.73 axle gears, would dance down the freeway at 80 mph without strain. (Of course the speed limit in my then neck of the woods use to be 75 mph.) This jeep was my daily driver at the time.
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