T-14 Swap To T-86

Hey guys I have a 1970 cj5 with the dauntless v6 and my t-14 decided to break on my way to the store earlier, I know the t-86 is a downgrade of a transmission but I have an extra one and don’t wanna spend the money to fix the t -14 the jeep has a dana 18 transfer case is there anything I should know before installing the 86? Thanks in advance for the help

 

The T86 is 3/8” shorter OAL but your crossmember should have slotted holes that allow for that length change.
However the T 86 front propeller shaft is approx 1” shorter than a T14 front propeller shaft.
Also the T86 rear propeller shaft is approximately 1” longer than the T14 propeller shaft.
Also the T86 (6 spline) and the T14 (10 spline) mainshaft ( output) gears are not interchangeable.

 

so I need a different output gear and propeller shafts to change it?

 

Other than that, it's a bolt-in!!

 

FYI getting a custom made front driveshaft for the Dauntless equipped Jeeps is not cheap. The small diameter tube and small u joints are not common. Unless you can locate used driveshafts for this conversion it might be cheaper in the end to fix your T14.

 

I would fix the t14 as well. Having the synchronized first gear is a huge plus.

 

The prop shafts may work “as is” but then again they may not ???????? Certainly not worth the effort to change them from a cost perspective.

Otherwise this should be close to a direct fit.
However there may be other small differences too like minor transmission cover fitment issues ?

I have no direct experience here, just thinking it through. The main difference being the 3/8” OAL.

I’m certainly with the “fix what you have” group.
You can likely sell the T86 to someone doing a proper vintage correct restoration.

 

I don't know about the earlier T86 equipped Jeeps, but the T14 Jeeps don't have slots on the crossframe or frame. Mine is apart right now:

Frame:


Crossframe:

 

What broke in the T-14? These Borg-Warner 3-speeds are easy to work on. The T-86 is basically a T-90 with helical sliding gears and main shaft - pretty significant downgrade IMO, plus the output gear and length issues.

 

I broke two T-14's before finally upgrading to the SM 420.. it doesn't take much..


edit.. I read that post wrong.. what broke in it.. not what broke it.. haha

 

Bizzarely, my 70, the frame wasn't slotted, the crossmember was. It's entirely possible that it wasn't the original crossmember, who knows. I ended up having to drill 2 new holes in the frame when I moved the crossmember back for my T98 swap

 

Slotted crossmember on my 67 with T14, no slots in frame.

 

Right I was referring to the late 1960’s to early 70’s crossmembers , many of which have multiple slotted hole patterns to accept various transmission insulators.

 

You can just cut the extra length off the splines of the front shaft just check how much travel it has before bottoming out. It doesnt move much with the shackles in front. At droop it gets longer. The rear will probably be fine as it is but you can check. it will probably pop the cap off or just show a little splines if it comes up short. But the extra 3/8" certainly wont make it not work.

 

The transmission difference is only 3/8” but the propeller shafts are near 1” difference.
One might expect that is due to the T86 shafts not being quite right.
The T86 propellers possibly did not compensate for the engine change ?
To date I have yet to study why Jeep was making so vary many subtle changes to the propeller shafts.

 

I was thinking of the wrong spot. Lots of holes and slots in the 71 crossframe where the transmission mount attaches.

 

No kidding, definitely the weak spot. Of course with the 420 swap, both shafts would need mods.