Inliners International Forums General Discussion Engines 4 banger guys,anyone ever use two transmissions for overdrive?

I'm looking for period correct late 1930's -early 40s overdrive ideas for an early hot rod I'm building.

I know a fellow out in CA by the name of Dave Kruger mated two model A transmissions together successfully,...this gave him overdrive,...spoke to a friend of his and he tells me they were cruising at 85 comftorably going to Paso Robles in a Ford 4 banger! it can be done successfully,....I'm just hoping someone has done this n here and can tell me how, etc.

Thanks in advance.
J.

the second tranny would have to be mounted backwards. it could be done but you would have to make some adaptors and couplers. tom

yes I believe this is exactly the way Kruger has his set up,...backwards to the one in front....

I'm a member of the www.67-72chevytrucks.com forum and IIRC, a guy did this with a diesel engine and there was a post on it about 2 years ago. You could ask the same question over there -folks are very knowledgeable and friendly and I'm certain you could find an answer to your question!

60 or 70 years ago a lot of guys used to hook two transmissions together to get more power to pull very heavy loads and that worked well when you turn the rear trans around to make an over drive the main problem you had was the input shaft was designed to be held centered by the clutch and pilot bearing so if you didn't make an extra bearing suport for it the bearings in the center of the transmission were short lived. so you will need to pick a trans with a large enough input shaft to be able to machine it for a support bearing or build an intermediate shaft that will accept the clutch spline on one end and the driveshaft yoke on the other and mount it with two heavy duty high speed pillow block bearings with lock collars to prevent the shaft from moving forward and back. The new shaft must be mounted in perfect alignment with the output shaft, and so that if the transmission moves under load the shaft will stay in line. When you over drive a transmission you are creating continous loads that the old trans was not designed for. Once you was under way and shifted to high gear it was a direct drive with no loads on the gears but when you start to over drive you will be running in second gear on the back transmission mile after mile. This was the problem that had to be solved with modern O D transmissions and that is why many tell you not to tow a trailer in OD

The intermediate shaft can be made from an old output shaft for the rear splines then Guys made the connection for the trans input shaft by machining a tube and that slid over the end of the output shaft and allowed the input shaft to slide inside then they took a clutch hub and set it up in a lathe turned a small shoulder to hold it square in the end of the tube and welded it and the intermediate shaft to the tube with multiple pass welds then chucked it back up and machined the weld just enough to make it even so they were near balance.

Sorry for the long post but I hope this helps.

To add to the above I have never done the twin trans conversions for power or OD but this is the way dad and Grandad did it. You seen more of this in states where guys raced top end. I knew a fellow from Ill. that had a flathad merc with OD and a 2 speed rear end that was able to lay modern cars to rest in the 60s if they wanted to race top end. If you want to think of a scary thought , think of the tires we were running back then. Then think about the 20s & 30s cars with mechanical brakes. Its a wonder anyone is still alive.

Does anyone know of any pictures? I would love to see this!