4 speed or 5 speed tranny?

[CJcountryboy]

I am looking to get my first cj soon, and I am unsure whether to get a 4 or 5 speed. Would a 4 speed run high RPM's on the highway or interstate? I will be mainly driving it to school and at the beach, but I will sometimes drive it on the interstate to our hunting camp. Thank you.

 

[BusaDave9]

The only 5 speeds to come in CJs were the T-5 from the '80s. These tranies were . Very light duty. Actually most manual transmissions from the '80s were . The T-176 was one exception. If you get a CJ from the '80s ask if it is a T-176 four speed.

If you get a CJ from the '70s they often came with good strong transmissions but a lot of them were 3 speeds.

The T-18 was the best tranny to come in a CJ. They were from the '70s.

Overall what I am saying is it's more important to get a good strong Transmission that a 5 speed.

For more info on CJ transmissions check out this link: http://www.jeep-cj.com/forums/f105/manual-cj-transmissions-12112/

 

[CJcountryboy]

So is a 4 speed ok for 65 mph speeds? Would that be pushing it, or is it more about gearing?

 

[BusaDave9]

So is a 4 speed ok for 65 mph speeds?

Yes

is it more about gearing?

Yes, It all depends on the gearing of the axles.
All 3 and 4 speeds have a top gear with 1 to 1 ratio.
5 speeds have Overdrive and for that reason will be running lower rpm on the highway IF the axle gearing is the same.

 

[BusaDave9]

When buying a used Jeep it is common for a PO to install bigger tires without regearing the axles. That has the affect of tall gearing.
When I bought my CJ5 a PO installed 35 inch tires without regearing. The CJ had a T-18 with Granny low first. Normally you would start out in 2nd but with the bigger tires it would be best to start out in 1st and then 4th was like an Overdrive . It all depends on the axle gears and tire size.

 

[BusaDave9]

You can use the above chart to see what rpm your engine would be at top gear at 65 mph. If you have a 5 speed the rpm will be lower yet.
Normally you would want to shoot for anything in the green but if you are buying a jeep just test drive it on the highway and see what rpm it is running.

 

[Saddle Tramp]

Check this out. It shows RPM in relation to tire size and gearing in the pumpkins.

http://4lo.com/calc/geartable.php