Transmission swap?

Doe's anyone know if a T15 transmission can be swapped in place of a T14 transmission? I am using a T14 and a Dana 20 from a 69 Jeep with the factory T14 adapter to Buick/Chevy bolt pattern on the bell housing. Is the T15 a lot better transmission and is the out put shaft 6 splines or 10 splines like the T14? I would like to get lower gears in my Dana 20 and there are no 10 spline gear sets from the after market kit builders for this set-up. I do not want to put in a truck four speed as this Jeep is mainly a street Jeep, but the transfer case is too high geared with the 4:27 axle gears I have in it now.

 

The T-15 Can be swapped in very easily. Minor mods only. The T-15 is 6 spline output and T-14 is 10 spline. T-15 is much stronger. Gear ratios are a little different but I don't remember which is lower or what the individual split is of each tranny. JPFlat2a might know that off the top of his head. Nickmil

 

T-15 is 3.0, 1.7, 1.0, 3.0R approximately. T-14 is 3.1, 2.4, 1.0, 3.1R also approximate.

Main difference is that the T-14 has a somewhat lower 1st, (by 3 or 4% IIRC) and the T-14 second is much lower. The T-15 2nd works better as a passing gear, but some like the small separation between 1 & 2 with the T-14.

Go T-15!