R-10 Borg Warner Overdrive Custom Installation and Operation

"Hello Doug,

I just left a comment on your blog about the Nash OD unit in the 37 Chevy truck...well done BTW!!

I've been trying to find an original R10 OD unit from a early 50's Plymouth, but they are rare and expensive. I'm doing away with the fluid drive in my 48 Desoto for a dry clutch, 3 speed manual. I had been toying with an idea very similar to what you did on your 37 Chevy. I would appreciate a little more info about the R10 unit you used, and what was involved with making it a stand alone unit. My system would be an open drive shaft set-up, but I can have plates and yokes machined to work. Also I'm interested in how you set up your control system, mechanical, or electrical?

Thank you for your time, Brian"


The drive line coupler from the mid 1930's Ford works pretty well on one end and the front shaft can be cut down to accept the same. A flange plate had to be fabricated for both ends on mine but with yours, you would only need to do that on one end. And different applies for the yoke situation for the open drive line as well, opposed to the closed. The open drive-line overdrives are far more plentiful than the enclosed style that I used. I do have another one as well as extra parts, seals etc. most of which would interchange with all.

I eliminated the kick down switch and the mechanical shift lock out safety, on the unit itself. I ran the governor ground/switching circuit through a toggle switch on my dash, before the electric relay. This allows me to be more in control of shift timing. I can split gears with it set up this way.

The down side of removing the safety devices is that you can literally split gears if you operate it improperly.

First engaging the mechanical control with the cable is important. Secondly switching the toggle. The governor kicks in at 25mph which grounds the relay and sends current to the solenoid, which will then engage the mechanical, provided you have the cable pushed in. Engagement won't occur though, until you have no torque coast. This situation is normally achieved with releasing accelerator pressure, however I use the clutch as well in second over but not third over. When I shift to third from second over, I flip the switch down, release accelerator,clutch in, shift,accelerate, and then flip the switch back up, release accelerator to achieve third over.

Fast acceleration shift goes: first gear, second gear, second over, third, and third over.
It gets down the road!

Downshifting is where you can loose your gears easily. Most people won't attempt to mechanically shift out of overdrive while moving. The downshift must be performed as follows: Flip the toggle switch off, apply accelerator in order to gently take up all slack in the freewheeling mode and then pull the cable to achieve lock up again. If you pull the cable at the wrong time, it could mean it's time to replace gears.

I believe it is also critical to run synthetic oil in your Borg Warner R10 overdrive when it is a stand alone unit. It creates a tremendous amount of heat which is probably dissipated better when it is a part of the transmission.

Photo courtesy of Chris Shelton

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