Swap T90 Transmission Behind A Dauntless V6?

Hello and thanks for taking time to read this.

My 1970 CJ5 drivetrain has a leaky transmission, I've done the easy things, reseal the bottom plate where it was seeping and teflon taped the speedometer threads. Over the winter I'd like to address the leaks, my question is, if rebuilding the transmission (T14?) would it bet better to find a T15 to rebuild and swap in? Am I right in reading that the T15 is a more robust transmssion?

Thank you!

 

The T15 is a pretty strong transmission, likely the strongest 3 speed. I’ve never done a T15 in anything that it wasn’t available in (AMC intermediate). You need to know the input shaft stick-out length and trans bolt pattern, front and back.
-Donny

 

I'm in the same situation. My t86 has seen better days and is not worth rebuilding. Is there a T90 variant that would swap right in? Don't mean to hijack your thread.

 

I may be mis understanding your question but here goes anyway.
Your T14 doesn’t have a pan or speedo cable, both of those are on your D18 transfer case.
As for swapping a T15, I am clueless but I would guess that adapters would be involved.
Rebuilding a T14 is pretty straightforward, but based on my experience, I would read up on tolerances and min/max measurements on the pcs you will reuse. Mine is not sounding very healthy after 2 years and 2k easy miles.

 

Lots of transmission info Here
https://www.novak-adapt.com/knowledge/transmissions/manual

 

T14 is a 10 spline output, unique in the Jeep world. T90 or T15 would have a 6 spline output. So you're going to need a 6 spline gear for the transfer case.

 

Just my opinion. The T-14 will be the weakest trans. The t-15 will be likely be the strongest but it is longer overall and would likely be the most difficult to adapt. Especially since they were never offered behind the V-6 as far as I know. As Donny said above they were only offered by AMC behind the V-8 engines. Also I have found some of the parts for the T-15 are a bit hard to find. As far as the T-90,It would likely be about as strong as the T-15 and parts seem to be a somewhat easier to come by. Probably because they were so widely used and for lots more years. however adapting them to the v-6 is not my expertise,. I will say this about the T-90. Years back my brother had a friend with a 3B with the t-90/D18 and a hopped up Ford 289 4bbl.He was a hot rod kinda guy, every where he went he was spinning and leaving black marks on the pavement with it. He drove that jeep 10 years and finally sold it. Never did have the first problem with the T-90 or the D-18. But rear axles were another story.

 

https://www.novak-adapt.com/catalog...ransmission/gm/jeep-t18-bh-adapters/kit-1415/

 

The easiest way to put a T90 behind the V6 is to source the 71 one piece bell housing, drill and tap it for the T-90.

The input shaft for the T-90 has to be the long one as used in the trucks, so that has to be swapped. I just sold one of those bell housings which had been fitted for a T-90. Problem is that bell housing was only made for one year before Kaiser sold out to AMC, so they are a bit scarce, but they can be found.

 

Two straight forward ways to put a T90 behind the 225. 1: use the T86 case and replace all the internal parts with T90J pieces. 2: use a complete T90J with the 2 5/8" adapter plate. Equally good. The 68 CJ 5 I bought from Fireball has the adapter plate/T90J setup.

 

Thank you everyone for your replies, it sounds like my best bet then is to rebuild the T14, again thank you for your time taken to reply!

Dave

 

Rebuilding the T14 is easy. That said pay very close attention to the gasket on the front bearing retainer when rebuilding, none of them fit good and they tend to block or slow the oil flow to the front bearing causing premature wear. My T14 has way more than 180,000 miles on the original gear set. I have rebuilt it but have used all the original hard parts.

 

Id rebuild the t-14 for sure. Good match for the v6. but sounds like most of your leaks are from the t case which is always the case theres not much to leak on the transmission.

 

T15 is an easy swap with parts readily available. The only good thing about a t90 is that it fits in a garbage can with the shifter still installed and besides a t84 is the weakest transmission ever installed in a jeep. A rebuilt t14 can also be easily sourced if you are not handy with modifications and driveshaft alterations required with a t15 swap.

 

Great information, thank you all.

 

I don't have quite that level of disdain for the T90. It wasn't anywhere near as over-engineered as the D18 but still a decently solid transmission capable of handling considerably more power than either 134 could muster. The T84? If one actually has one of those in hand, they are TINY. Willys wasn't the only application of those either. My 41 Nash 600 coupe sports a side shift T84. Those wouldn't make a bad motorcycle trike transmission if they actually shifted worth crap

 

I blew up 2 or 3 T90's, but it was a heavier vehicle (IH Scout) with a decently strong Chevy 327 and perhaps most importantly, I was 17 years old
Years later I put my CJ together with a T90 and it lived for over 20 years behind a Dauntless. i drove it much more conservatively!