Which tranny behind a 225 v6, T86 or a T90

Hey guys, which tranny do you think would be a better tranny behind an odd fire. a T86 out of my 66 cj5 or the stock T90 that came in my 47 cj2a ? I'm building the 47 and installing the dauntless from the 66 and wondering which way to go. I also am using the TC out of the 66 to get the desired 1 1/4 cross shaft. I have a T-18 from a cj, but thinking I may want to hold that for another v8 build later on down the road. I'm running 538 gears. Let me know what you all think, Thanks

 

The T-90 from the cj2a (4 cyl) will not adapt to the 225v6 without re-drilling the tranny to bell adaptor from the 225v6. Also the T-90 will require the install of the longer "J" input shaft to work with the v6 and also a pilot bushing change. Transfer the complete running gear from the 66 to the cj2a.

 

As Walt said, "Transfer the complete running gear from the 66 to the cj2a". The T-90 adaption is not worth the effort. To go through all that get a sm465 or sm 420 and have less trouble.

 

I'm gonna disagree with the 2 above. The T86 has a very poor durability record (in fact, Jeep onlt used them for a couple years behind the V6 before switching to the T14. I've been running a T90 behind my dauntless for a dozen years with no trouble...it's certainly not the ideal trans, but it'll last if you don't beat up on it.
Walt is correct on the steps needed to adapt it to your 225.

 

A T-86 is basically a warmed-over T-90. The only differences are the front case pattern, the angle of the sliding gear teeth, and the spiral in the mainshaft splines. Theoretically gears with helical teeth (T-86) are not as strong as gears with straight teeth (spur gears, T-90) but they are quieter. Unless you are breaking 1st or reverse of a T-86, I think it's hard to attribute superior characteristics to either transmission based on their design.

My feeling is that Jeep replaced the T-86 mostly to get the "modern" all synchro 3-speed in the CJ. A non-synchro 1st was pretty old fashioned by 1966.

My main concern about a T-86 is lack of replacement parts. There are lots of T-86s out there that have busted and are now T-90s with a T-86 case. Replacing all the gears with T-90 gears is the usual cure for these broken transmissions. The T-90 gears drop right in, but you cannot mix T-86 and T-90 gears.

If you want a 3-speed, go with a T-15, which is stronger than any of them.

 

Any non synchro 1st gear 3 speed transmission is an absolute waste of time for driving in any traffic. Unless you are doing a museum restoration there are so many better options out there. Most times the statement " I already have the parts" is one of the most expensive that you can make. If you have a T-18 4 speed transmission that will work with a Buick bell, that is by far your best bet.

 

I've driven mine with the T90 for over a decade....I live in a medium large city with lots of traffic.
Is it ideal? No. But it was what was on the budget when I put the Jeep together. The 225 has enough torque, especially with 5.38's, that you don't need to use 1st unless you're at a complete stop.
If I was the OP, & I didn't have a ton of money for the T18 swap, I'd get a long T90 input shaft and a small parts kit, Rebuild the T86 case with the T90 internals, & be done with it.

 

I ran an adapted T90 for 29 years behind my V6, never had any troubles, trails or city driving.
With that being said, the concern for me nowadays would be replacement parts for the T90.
The offshore junk is just that...junk.
If you can locate original OEM parts, shafts, gears etc, then do it.
The adapter can be had for almost nothing nowadays, just gotta look for one.

The 4 speeds are a lot of work and effort.....and some costly components.

Ditch the T86 idea...junk transmission from the very beginning.

 

It's a very tough decision to make indeed !
Because once you decide... then everything that comes afterwards depends on your previous choices.

You need to take a good hard look at the complete project and decide how the jeep will actually be used in the real world.
Remember the jeep should always be envisioned as a complete and synchronous system.

The stock 2A frame is not a great candidate for use with low FDR like 5.38 compounded by a T18 and the extra HP.

The V-6 can be strong running and it will match very nicely to the strength of a Borg Warner T15.
You really wont need to "BABY" the T15 nor the V-6.
Besides that the T15 fits the D18 like its made for it (TEXAS pattern) and you could install a T15 without relocating the D18.
Oh by the way you will need to swap in a big hole D18 for the T15.

 

Thanks for all the input guys. I do have a big hole D18 already. The t-18 was my first choice for the swap and thats why I bought it. Its a lot of tranny for the 2a and over kill, but I would never have to worry about it once in the build. I have never found a T 15 anywhere around my area in Mass. Sounds like it would be a good fit for what I'm doing, with the parts I have on hand. May have to start looking for one around here or local enough to pick it up. The frame for the 2a is coming home tomorrow from the blaster. Have to repair the normal spot up front on the right horn/frame area and then box the frame. Then I have new springs coming that are a bit longer. I wanted the frame in por 15 by next week and then begin to align my new drive train, but I can wait as I only want to do this build once and not worry about it. The barn will be busy this winter for sure. To take my mind off it today, I stripped my 93 YJ interior to the floor today, (including seats and belts) in hopes of getting it cleaned and sanded for bed liner later this week. I was pleasantly surprised to see the floors are 100 % rust free. Makes the rest of that job much more pleasant. I will begin to see if I can find a 15 around. Keep the ideas coming. Thanks again.

 

If you are considering the T-15, realize that you'll need an adapter to the GM BOP bell that the 225 uses. Novak sells an adapter, and it's not wildly expensive: http://www.novak-adapt.com/catalog/adapters/engine_to_transmission/kit_1415.htm

The T-15 was the only transmission for Jeep CJs 1972-1975 with the 304 V8, and was the standard transmission the 72-73 Commando with a 304. It was also the standard transmission for J-trucks, Wagoneers and Cherokees (FSJs) in the late 60s and 70s. However, the only FSJ application that will work in a CJ is with the 258 inline 6, 1975-1979. The V8 T-15s have a very long input shaft and adapter that is not suitable for use in a CJ.

Note that the T-15 was fine with 2V Buick 350 or the 2V or 4V AMC 360 in a Wagoneer or low-GVWR J-truck. No problem. And it's a much easier shifter than a T-18 or other truck 4-speed.

 

Yeah like Tim said the correct adapter is a must.
It will be 1-5/8" thick.

One good thing about the T15 is that it uses the standard floor shift pattern.
That makes it really easy to "rock" the jeep back and forth when it is stuck in mud.
We have all types of mud in my area.

 

Anyone know where there is a T15 fo sale?

 

Put an ad in the Classifieds?

 

In my area they show up on CL about 1 per year.

 

oldtime, that does not make me feel any better. But its about the same up here. But I'll start digging.

 

Well good news. I have found a T 15 here locally, thanks to Endangered Species Jeep. It has the adapter 1 5/8 thick, mated to a GM bell housing and a Dana 20. TC. So it looks like I have most of what I needed in a single lucky purchase. Separated the tranny and tc today and opened the top cover. Looks ok, but I think I will do a rebuild with Novak kit. Any good links for a T15 rebuild here or anywhere? Been looking but doesn't seem to be much out there. I have been looking and reading about the t15 and it seems to be a good choice for my build and motor combo and I like the fact that I can rock it. There is no way to rock a t18 without grinding off a lot of metal. So if you guys knows a good site for a rebuild info, let me know.
PS, the frame is in the barn and going together nicely. Put on 4 new rear springs on all corners.

 

The T-15 is a good transmission. Jeep used it as the standard transmission with the 2V V8s in the J-trucks and Wagons, and it held up just fine. Plenty strong enough for a CJ.

So basically you just want to freshen up your T-15? If it were mine, I'd probably run it before I thought about going through it. That would tell me more about what it might need. If it were quiet and shifts ok, I'd leave it alone. And if it needs some work, it's not that hard to pull a B-W 3-speed transmission from a Jeep - I've done it in my driveway in an afternoon with muscles and the factory jack.

 

Yeh, I went through it last week and decided to just get a new gasket set, seal it up as tight as I can and paint with por15. I'll use it as is and it looked like the previous owner may have gone through it already, all the needles look really good and I see no pitting on any bearing surfaces. The gears look good and they shift back and forth with little effort. So I will button it up and use it.