Is the trans up shifted by electrical servos or by hydraulic like the old 727? If elec then why not just use micro switches to up shift and down shift( full manual ). The speed sensor iis inside trans and works with the abs sensors plus main controller. Reason I know the mechanic next door spent two months with the help from the Dodge shop trying to find the problem with a 2011 Charger. The trans would go into limp mode, tried everything, two trans, new sensors, changed tires. Come to find out the previous owner had changed to an SRT8 rear(3.06 ratio) and main controller was programmed for a 2.65, so the sensors couldn't jive and kicked it into limp, even the main engineers from Chrysler couldn't figure this out. Changed back to an original rear and trans worked fine.But chrysler did say the tires had to be within 5% of stock size to work properly(same as changing gear ratio). We think the rear package came with a chip box but was lost with selling the car to dealer to used dealer. As far as using Jeep trans I think they are independent (bolted solid to frame) so no u-joint either, I didn't see the type of slip u-joint you used in your build up pics other than the aluminum piece.
Edit; got the original trans and going to pull it down to see if my idea would work.
I am NO expert ,in fact very novice, about exactly how transmissions work, particularly the new computer controlled ones but....I do know that Russell had us save a file of how the thing was working and send it, the computer itself, the rear gear, and the tire diameter when he re-programmed my unit. Obviously all of these components have to line up like the stars for everything to work properly. There was some discussion (mostly talking from Russell) about pressures and signals so I am pretty sure it is a combination of both that actually cause the transmission to shift when it does.
I should have this thing re-installed sometime next week so I can report on performance.....or not.
