T 86 trans question

Hey everybody so had a rough Monday because I found out my transmission is blown and I have a couple questions.


Is the T 86 worth rebuilding? And if it is how much would it cost? Or is my money better spent by doing an SM 465 or SM 420 swap?

The Jeep it's in is a 1968 CJ5 with a Buick 225 V6. I'm only 18 and this is my daily driver/toy with that said the Jeep will be playing in the mud and some light trails so any advice and opinions are welcome!

 

Eh ... define what you mean by "playing in the mud" and "light trails." The T86 wasn't really known to be an especially strong transmission, given that it took Kaiser-Willys all of a year or two to stop using the T86 in favor of the T14.

A quick look around suggests that parts for the T86 are available, and it's supposedly no harder to rebuild than a T90 ... but it doesn't appear to enjoy near the support of some other Borg-Warner gearboxes, or the Muncie gearboxes you're thinking about.

 

The T-86 is essentially a T-90 with a different case and some internal refinements. The main shaft splines of a T-86 spiral, and the 1st and reverse gears are beveled. The T-90 has stright splines and straight cut gears.

This means that none of the gears will interchange between the transmissions. However, you can take T-90 gears and put them in a T-86 case, if you use all the T-90 gears. Reuse the T-86 case and it will bolt up to your existing transmission-to-bellhousing adapter. This is the usual fix for a broken T-86. If you search old posts, you'll find a lot of discussion of this topic.

 

To add to what Timgr said, one shift fork in the top needs changed as well. I want to say the first-reverse fork but would need to double check.


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How did you blow the t86? I'm asking cause depending on what you where doing might give you an idea on whether to keep it or swap.

Depending on what is broken will determine how much it cost to fix, rebuild kits start at 100$ and go up depending on extra parts needed. Like gears and such..

I had a 65 Chevy when I was 18 and the 66 jeep, I kept the jeep as toy. The truck was my daily driver so I could do upgrades and still have a car. Sometime later I got rid of the truck, and I walked a lot. I still do, too many good upgrades to do to the old girl. With that being said that sm420 in the 65 Chevy was bullet proof. Was never afraid to break that transmission with that Chevy 350. Almost parted the truck so the jeep could get the transmission.


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If money is an issue (I'm guessing it is, since you're 18 ) I'd go the T90 route. As Warloch posted, a 4 speed swap is gonna get expensive.
One other thing to consider....when I was a teenager, I blew up several T90's, because I drove like a teenager!
None of the early Jeep 3 speeds (except maybe the T15) are up to speed shifting or hard abuse. Take it easy on the trans, especially when shifting, and it should give you good service. I've been running my current T90 behind a :v6: for over a decade now.

 

Now this brings up a fascinating question on my part and that's ... if the T86 is a refined T90, then why is it that I hear that the T90 is okay to slap behind even modern V6s and small-block V8s, whereas the T86 isn't retained in motor upgrades?

 

Well, the only difference I can think of is that straight cut gears are somewhat stronger than bevel cut gears. Bevel gears are quieter though. But that should not mean a substantial difference in strength.

I think it all depends on the perspective of the poster. When you swap a V8 into a Jeep with a F134, you have some understanding that you are stressing the drivetrain components more than they were originally designed to be stressed. When you buy a CJ-5 with a V6 and T-86, it's a factory setup, and heck - it's a tough, rugged, unstoppable Jeep! Which scenario is more likely to lead to abuse?

You can blow up any drivetrain component if you apply the proper abuse. Is the T-86 adequate for the 225? Sure, as long as you don't fit huge tires and pound on it in the rocks and don't speed-shift or burnout on the street and so forth. Will it break if you do? Yes. Will the T-90 break if you do? Yes. Do some people get long life from a T-90 behind a V8? Yes. Same with the T-86 if you treat it right.

I think the problem with this combo is that some (most?) drivers don't have the skill, knowledge or experience to understand what maneuvers are ok and what are not. Or maybe they lack the willingness to hold back when they should. And you never know when you've gone too far until it breaks. If you have stock sized tires and only putt along on forest service roads it's clear that the T-86 or the T-90 will be fine. From there, you have to use your judgement re what is appropriate use and what is abuse. If you abuse it, it will break.

 

Well I'm assuming the reason it blew is because. This was my first car and also my first stick shift which I got the hang of after grinding some gears and not knowing what I was doing. As far as speed shifting goes I never did that in my Jeep my family is a drag racing family and has been for ever but I knew Jeeps weren't meant to drag race. Now I did go and abuse it in the mud and the snow we had this year. Also I might add it does sit on 33's which the PO had put on and when I got the Jeep I had no idea what I had as far as transmissions go. So now I just want to know should I rebuild it as a T 90 or save and swap something else in.

 

Depends on you and what you expect from the transmission.

Consider the odds, place your bets and take your chances.

 

Simple. Parts are readily available for the T-90. Not so for the T-86. It's really not a strength difference between the two.


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I am currently rebuilding my T-86. I needed a reverse idler gear, cluster shaft and first/reverse slider gear. An overhaul kit, cluster shaft and reverse gear were easy to find. The first/reverse slider gear was a pain to find. There is no repro for one so you have to find a NOS gear. I finally found one after weeks of searching. I thought about putting the T-90 gears in but after I figured the cost of doing that it was the same as the T86 parts I needed so I stayed original. If I didn't find that first/reverse gear I wouldn't oh had a choice.

 

FWIW I replaced my working T86 with a T14 that I had on hand just because I like to have syncro 1st gear and have a easy foot on throttle and clutch.I donated the T86 to Herm.He may still have it complete or parts. mike