Swapping A T-15 For The T90

I should start a poll, asking which would be the best replacement for the T-90. So which if any, transmission would you put in place of the T-90 with the stock F-134 ??

 

The t-98 is the easiest and most practical, since it was available as an option, but availability is slim so you'll pay dearly.

Beyond that option, whatever you choose will be a custom fabrication, so take your pick. Your T-15 would be as good an option as any I guess.

 

A T90 is well suited behind the F134, and the D18 has a better low range, plus allows for optional overdrive and pto devices. For the cost of adapters to make something else fit, why not just do a proper overhaul of the original trans/transfer case? No driveshaft changes, no floor cutting, no linkage modifications if you just keep the T90. Seems like a no-brainer to me.
-Donny

 

X2, that's what I was thinking the whole time I was reading this thread. The T15 swap would be a lot of work and expense for little gain.

 

I have a Dana 20 with twin sticks in my 47 right now, with the guts of a Dana 18 and Saturn overdrive . I also have a spare big hole Dana 18 out of my 66 cj5 with Dauntless. I have two 1 1/4 shaft Dana 18's in the sugar house for parts. The difference with the Dana 20 in my 47 2a, is the rear exit is passenger side for the offset Dana 44. I'm getting the feeling you guys are mostly against this. I'm looking for some encouragement......................

 

That makes it an 18, regardless of which case you used.

 

Encouragement ? Really ?
O. K. I won't mention any of the drawbacks. Ha Ha Ha

The Borg Warner T15 is a really truely nice Jeep 3 speed.
In fact I consider it to be the best Jeep 3 speed ever.
Strong and it feels real good when it shifts.
The ratios are fairly near optimum for a 3 speed although T14 ratios are a tad better.
Easy to rebuild and good parts are still out there if you look.
Great strength to weight ratio and size is fairly compact for its strength.
Solid cast iron.
The untapped side shift lugs can be cut off if you wanna save a little weight.
Simply the best transmission around that bolts direct without an adapter to a Dana 18 or 20 transfer case.

 

Thanks oldtime, Thanks, I feel a little better now. I'm thinking about using those side lugs on my T-15 in the 47 2a , as a mounting point for my hydraulic clutch cylinder. I have to drill and tap the lugs as mounting points for a bracket. colojeepguy, its still 18 gears, but a stronger 20 case and retains the lower gear ratio of the 18, win, win , right ?

 

I'm guessing not. From Novak: "The T15 is synchronized in all forward gears..."

 

No.

AFAIK transmissions with a synchromesh reverse do not exist. Having done this maneuver a few times, you need to use your judgement about where the limit between effective use and abuse is. The main advantage is the straight-line shifting between the two gears. Synchro in first helps, but you have to curb your enthusiasm shifting into reverse.

Also a T-15 is strong enough to put up with this for a while.

 

I'm not talking about slamming between first and reverse, but I have used it in my 47 and its a pretty easy shift between 1 and R and there is no grinding when done with common sense. Sometimes a gentle rocking can get you out of a semi stuck spot. Of course and before anyone mentions the winch, I know when to use that as well. You cannot do that with a T-90. A complete stop is necessary, between 1 and R.

So have we come to a consensus about trying this or not or option B, have we decided on a better tranny to replace the T-90 ? Some of the main reasons I wanted to attempt this is, as mentioned in the prior posts, the T-15 is a much stronger option that the T-90, its not a lot more to ad in length to the drive line and it offers a usable 1st gear on the street and better to rocks the crap out of the cj5 when I feel like beating the heck out of it. (only kidding guys) I thought those were good enough reasons to think about it. I figured, with all the great minds here, we could come up with a game plan. Besides, don't you want to be part of the first ever attempted application ;-)

So maybe I have to admit that it cannot be done, but that has never stopped me before, but maybe this time. Admit, it got you all to think about it, right ?

 

I'm not really sure what it means to say, is it synchronized between reverse and first gear. I can tell you that sometimes moving forward at a little crawl, its possible to put the t15 into reverse and not even feel it go in, same going the other way. Not sure if that qualifies as synchronized between them, but possible. We all have done it, intentionally or not, but the clutch is all the way in.

List transmission you would use instead and I will start a poll to see who comes out on top in a week or so. Remember, overall driveline length is pretty important. At least 3 forward synchronized gears, not excluding a four speed with a non syncro 1st.

 

First poll started in very first posting

 

Anything is possible with time and money...
So if I read your post, the only reason for doing this swap is so you can "rock" the Jeep back and forth without grinding into gear ?
That's gonna happen with any manual transmission.
So, don't get stuck would be my answer here.
One more comment: T90s are a dime a dozen, T15s... not so much.
Guess how I'm gonna vote in your poll ????

 

It's nearly impossible to break a healthy T-90 behind a 134. "If you can't find'em, grind'em!"

But... I despise unsynchronized gears. I can see the appeal that you see. Personally, if I was going to do the amount of work that is ahead of you, I'd fit a more practical 4- or 5-spd rather than a 3-spd. The less power you have, the more gears you need to keep an engine happy.

I adapted a J-series pickup t-18 to my F-head with minimal money and good results.

I believe NV4500s, 3550s and 3500s are fully synchronized, including reverse, aren't they? But adapting any of them to a D18 is lotsa money.

 

I see how it is.......... I can tell how you two voted. But that's part of the fun of this post......jpflat2a, you missed a few of my other reasons for doing it, but I guess I couldn't break a Dana 18 behind the f134 anyways, or could I And I would never place my early 5 in a predicament to ever get stuck anywhere, after all, its meant for the street right I'm starting to feel a sense of , well maybe, this isn't going to happen. I was looking for the Jeep guy in all of us to come out and push me forward, but maybe, your pushing me straight instead.

 

You have not seen my 47 yet, if you had, you would know, I'm not afraid of a little pain or maybe in the case of the 47, a lot of pain in my #@* . But I love every minute of it, after I figure out how and then get it done. Got to love Jeep people. I would love to do a T-18 some day, but in a longer series of CJ. My Scrambler is already set up for the 327 and mechanical 700R4 with a Dana 300. Only thing I'm going to do, is install a Terra Low kit in the 300. But that's after the early 5.