Re: Installation of an override gear from 1951 Mayfair 250 in 1936 One-Twenty

Posted by flackmaster On 2016/7/23 18:51:53

First, the input shaft collar, and the throwout bearing are different on a 36, so that would have to be changed to the later style throwout bearing. Not difficult.
Second, the output flange definitely is different on the 51-54 unit. Definitely would have to be changed, likely best to adapt to a modern flange for both the transmission and the driveshaft. Moderately difficult, mostly because of the reasonable level of research required to identify what would be available to you. If you need further consult on this, please reply as I have one of these 51-54 units here that I really should resolve this for. Modifying the driveshaft should be otherwise straightforward for a driveline shop...
Third, the frame on your car will definitely have to be opened up to accept the R11. I've seen it done many times. Moderately difficult, and then tight quarters to work in.
Fourth, and the biggest challenge is the 51-54 transmission case is not drilled and tapped to mount to your transmission mounts. Can be drilled and tapped, plenty of metal there to work with, and also I would suggest a custom crossmember to take advantage of the 51-54 bottom mount, in particular so we don't have to confuse you with discussions of the infamous snubber. This is definitely getting towards the difficult rating, but certainly can be done.
Fifth, it is strongly recommended to properly clean and service this transmission before installing - 60 year old gear oil is notorious for being too sticky by now, and without proper lubrication, these overdrive sections can turn on you in a bad way. Also maybe with the guts out (lighter being a relative term), you will be only slightly more comfortable assessing the required frame modifications.
Sixth, Electrical requirements are pretty straightforward and available, but you will still be fabricating a custom harness. The accelerator linkage does not have an accommodation for a kickdown switch - which is otherwise very easily wired, associated with the accelerator pedal, or dashboard mounted...its just a momentary interrupt switch.
Finally, a custom speedometer cable will be required, simply a BW overdrive on one end, and 36 speedo on the other, length as required. Speedometer will not be accurate, but GPS readings and tape on the face of the speedometer will suffice.
Oh, and adapting the shifter top falls into the moderately difficult strata only because extreme care and patience is required.

Welcome to the Church of the Holy Overdrive, amen to Autobahn speeds.

Guscha - please translate/assist as required, and by the way, I am awaiting further information on the Germany 2017 meet....need to make my chauffeuring reservations.