Re: Replacing standard gearbox with an overdrive gearbox 1948 22nd Series

Posted by HH56 On 2010/8/3 8:18:47

Car is progressing nicely & like your color choice. Is that the new demister you found locally? It almost looks like it might have been there for 60 years.

There were two overdrives available. The cars would probably have had the R9 when new. Those had carried over from prewar and was replaced by the R11 in 49. There was a program where the R9s which were sometimes temperamental could be replaced with the newer units so it is possible the later is what you have offered. The entire trans and OD assy is changed as a unit. Driveshaft is shorter and there are some different and additional brackets for cable controls and switch mounting needed as well. There were also some gearing differences in the rear axle but I can't speak directly as to what kind of results you would have if that was not changed. If you have access to the parts car, and it is fairly complete would be a good idea to get as much as you can.

The R11 would be the easiest electrically as there was only 1 relay and a couple of switches as compared to the older unit. That one was much more complex electrically and mechanically. R9 electrical parts are starting to be hard to find and expensive. R11 components are being reproduced as they were used by lots of other cars in the 50's. The manuals for both units are available on site--look for econo-drive for the R9. The R11 is covered in the Borg-Warner OD book as well as a service counselor from 49.

As to the advantages, it seems to be a popular upgrade over here lately but will let those who have made the change answer that question.