t5-258 6

will the T5 transmission bolt to the 258 straight 6 or will I have to do a lot of modifying:? also were might I find the numbers to tell me what transfer case I have.

 

It will bolt up, but that will make for one long drivetrain in a CJ5.

What year is your Jeep???

High5

 

CJs came with T-5s for a few years.
http://www.jeeptech.com/trans/t5.html
One of those will bolt up to a 258. If you have a T-18, it came with a Dana 20. The Dana 20 will not bolt up to a T-5. I think it would be a huge mistake to replace the T-18 with a T-5, but if you did, the easiest route would be to swap the transfer case too.

There are pictures of transfer cases on that site. Only the Dana 20 and Dana 300 (D20 and D300) look similar. Look at the rear output housing of your transfer case. If it's cast iron, and it looks like a D20, it's a D20.

There are some more pictures here: http://www.novak-adapt.com/knowledge/transfer_case_gateway.htm

If you want better fuel economy, the easiest and most effective step is to reduce your highway speed. This will have a much bigger effect on economy than swapping the transmission. Wind resistance goes like the square of speed, and speed makes a big difference in fuel consumption on as un-aerodynamic a vehicle as a Jeep.

Fuel injection will also improve economy. The GM throttle body injection (TBI) and Mopar multiport injection (MPI) are both available as kits for the 258.

Another possibility is to swap in a 4.0L engine with MPI from a Wrangler or Cherokee. These engines are much more efficient than the carbureted 258.

Keep the T-18. Change your driving habits. Go Fuel Injection. Be proud of your CJ!

 

I have the T4/D300/258 set-up. Works great in my CJ5. No drive train problems at all. T5 is same as the T4 except extra gear! (From what I've been told)!

I have the 258 with the 4.0 Head and it's STILL carburated (kept the intake manifold) and I just went 101 miles in 4WD and topped off the gas tank with 5 gallons....not bad getting 20 mpg with a 258. BUT...going by what timgr said, I did NOT go over 50 mph (snow storm) and that saved my gas mpg BIG time!

You can read about my build HERE.

Near the end of the write up you will see the 4.0/258 Head swap.

R)