Swapping A T-15 For The T90

FWIW, I put a T18 behind the L134 in Ted. I did a bunch of machining and customizing, but it is by far the best thing I have ever done.

To make the swap as easy as possible, I made the front of the T18 look like a T90 so the stock clutch components would work. I bored out the stock T90 clutch release bearing sleeve (cast iron part the T/O is pressed on) and I used this bearing with it. I cut the rear flange off so I just had the thin OD and I pressed that into the cast iron sleeve. I made sure it was the same length as the stock T90 T/O bearing assembly. Then for the input shaft, I cut the splines off the T18 on, and the splines off a spare T90 one. I made the T90 one longer than what I needed so I could account for the adapter thickness and the alignment nub that was machined on the end of the T90 splines. The face of the T18 shaft had a hole bored in and the two halves were pressed together and TIG welded. I had a machinist do this and he said it was dead nuts straight. I also made a little adapter that moved the pivot ball up for the clutch fork. As far the adapter goes for between the transmission and bell housing, I had a 7/8" thick one that was used in a Jeep trucks that had the I6 and a T18. I drilled new holes that matched up to the ones in the T90 bell housing and just bolted them together seeing how the hols in the bell housing were tapped. I also put two alignment pins to keep the bell housing and adapter centered. I also moved the clutch linkage back and used a cable from a Willys truck that had the T98 in it.

And before anyone cries about the input shaft being welded, I have wheeled Ted like crazy and have had both lockers engaged and have towed some pretty heavy things with him and it has been fine.

So in short, it can be done. Just takes careful measuring and a little bit of ingenuity.

I also made a bracket that moved the transfer case and shifters up so they would come out of the original hole in the floor. The shifter for the transmission came out in the original hole too.

I used a front driveshaft from and intermediate CJ5 that had a 304 and a 3 speed and it was the right length. I had to make a super short rear one. The crossmember had to be moved back and I made an adapter plate to bolt the transmission on it and keep the D18 mounted in its original spot.

 

WOW, Nate, you have way too much time on your hands. I will put that tag out on the wood shed tomorrow morning.

 

OK guys, although I have the T-15, what would be an alternative 4 speed that would work behind the F-134 and not change the OAL of the driveline to dramatically ? If I'm going to a 4 speed, I would be looking for a low first gear and hopefully a syncro first gear, or would that be out of the question. I will continue to work out the necessary blueprint of an attempted T-15 swap, but thought I would ask about a 4 speed anyways, to weigh the positives and negatives.

 

Novak has a kit to swap in an NP435, but I think the trans to D18/20 adapter is long. Just looked - 3.5" long... not too bad.
Adapting the Willys Jeep L & F 134 Engines to the Dodge NP435 Transmission
Adapting the New Process 435 Transmission to the Dana Spicer Models 18 & 20 Transfer Cases

Otherwise, without going as custom as you would have had to go with the t15, the t98 is your only option. First gear isn't synchronized, but second gear is, and second is similar in gearing to the t15's first.

Are you looking for a bolt-in swap? Or just transmissions in general for you to adapt yourself?

The "3-ring" (3 grooves cut into the input shaft, as opposed to 1 or 2) Saginaw car 4-speed is a great jeep transmission in my opinion. 3.5:1 first gear, and a smooth, fast shifter. I'd love to drive a 134 with one in it. The trans is short, the adapter from Advance is short, and it is plenty strong enough for even a v-6. The only possible drawback is shifter location. it is a side-shifter, so the shifter comes out just in front of the corner of the gas tank. But as far as adapting it to the 134, you'd be on your own.
50-1000 : GM Saginaw 3 & 4 speed transmission to Jeep Dana 18/20 transfer case (with 6 spline drive gear),adapter kit. | Advance Adapters

 

In order to determine the ideal transmission I'd say the 3 Speed vs 4 speed is the sensible place to start.

A good Jeep 3 speed has several obvious advantages.
Lighter weight, smaller size, shorter OAL.
Generally it's easier (meaning quicker/smoother) to shift the 3 speeds plus the 1st to Reverse shifting is more direct.
The 3 speed should be a tad easier to rebuild.
They have a lower intiial cost.

The only real advantage to a 4 speed is the fact that the gearing range (torque vs speed) is notably increased.
The shortest possible 4 speed for use with a Dana 18 or Dana 20 is the Borg Warner T98 or T18.

The choice mainly comes down to ones real need for an expanded gear range.
For true crawling the 4 speed is a must.

I simply don't feel that car type 4 speeds supply a sufficient range.

 

I have looked at the NP435 as a choice and it fits better than most. I think the ford version is easier to adapt that the Dodge, if not mistaken. The OAL is pretty close. Its in the thought process.

 

I don't know if it would be easier/harder to adapt than the Ford or Dodge version, but International used that trans too. Just another option if you come across a cheap one.

I found an old, wrecked, low-mile school bus in a junk yard. We took the engine for my dad's dump truck and I put the NP435 in my Scout with a divorced NP202 behind it. I LOVED that transmission. Favorite granny 4spd I've ever owned.

 

I will probably head out to the bone yards after the holidays to see whats out there. Never thought about an International .