T5 Transmission Replacement Or Rebuild?

My friends Jeeps transmission took a crap and the transmission shop is saying it would probably be better/cheaper to find a new transmission rather then rebuild. Just curious on people’s thoughts and if there is a reasonable replacement that would mate up to the amc 258 I6 or is the T5 worth rebuilding?

 

Look at novak's website for ideas. They don't like the T5 at all.

https://www.novak-adapt.com/knowledge/transmissions/manual/

 

I'm stepping onto my soapbox for just a minute...
The decision for transmission model is the best place to start when fixing up or modifying an old Jeep IF it's a vehicle you plan to keep and drive. Always consider a HD truck 4 speed (or 5 speed if it will fit). Novak agrees.
A transmission swap can get expensive as driveshaft lengths may change. You may find that a new clutch and pressure plate are required. The hydraulic operated clutch makes sense for some. You may find the engine needs work if the flywheel comes off for a resurface. These are just the heavy hitters.
If your buddy just wants to get the vehicle running, find another T5 and have him drive it GENTLY.

 

I've always wondered if you can use the Jeep T-5 output shaft/case but swap in all the rest of the parts from a Fox body 5.0 Mustang World Class T-5 and have a much stronger setup? They aren't crazy strong in the Mustang application, but do take quite a bit of abuse.

There is some good T-5 info here, but they don't discuss the Jeep ones: https://www.motortrend.com/how-to/1506-everything-you-ever-wanted-to-know-about-the-t-5-five-speed/

 

Although the cases are the same, I don't believe that will work due to the difference between type of main shaft bears used in world class T-5's versus bushings used in non-world class T-5"s. Interestingly, years ago an aftermarket manufacture was making main shafts for the adaptive use of the world class transmission in jeeps believing the newer version would hold up to use of the more aggressive 4x4ers. That obviously didn't work out. The transmission just does not withstand the shock loads experienced in 4x4 use.

Others in the automotive world do like the T-5 transmission. You mention they were used in the 5.0 Mustangs with reasonable success and a member here (Dne007) in Texas has one in her '67 5.0 mustang. The street rod crowd from time to time, also use them. They like the aspect of the overdrive.

 

What year is the jeep and how many miles on it?

 

It’s an 83 cj7 with unknown mileage, probably less than 100,000, it is a hunting Jeep that sees mostly light off-road use, honestly rarely even needing 4wd. This last transmission has been in it since I was in high school, so about 30 years. I’m thinking for this jeep, rebuild is the way to go! I’m just not familiar with parts availability on this transmission.

 

NV3550 should work and keep the same 4:1 first gear. Plus you get hydraulic clutch with this swap.

 

I used to wheel with a guy who mixed/matched a mustang/jeep t5 to a D300 with great success, although he ran his behind a 5.0, so keeping the world class case was easy.

 

Your friends transmission is a non-world class (NWC) T5. If you decide to rebuild the transmission, I have attached instructions to do the repair. Parts are availability. For example, look up Motive Gear on the web and check their catalogue for the NWC parts listing. You should be able to find other sources for parts but pay attention to where the parts are being manufactured. The transmission lasted 30 years so with good parts it should continue to provide good service.

In addition to ITLKSEZ, I also know of a jeep with a Chevy v6, T5 and D300 that has been in use for a long time. It's not used for rock crawling but spends as much or more of it's time off road.

 

So the real question is what does he wan to spend and how much effort is he willing to put into it. The T5 has a bad reputation for being a weak transmission. Remember, street use isn't offroad use, where shock loads and unsprung weight are the norm. If the feeling is it will last, then a rebuild is the first option.

Since it pretty much never goes offroad, not needing a 5th gear gives you other options. A T150, T15, or T18 are popular. The will all require an adapter to the D300 T case, which along with driveline mods can get expensive.

The T176 is a good option. Strong and most came in front of the existing T case. They are fairly common and should adapt with a minimum of effort.