47-55.1 Overdrive Transmission Question(s)

[1project2many]

Are you sure it's ALWAYS in freewheeling mode? As in you are unable to reverse the truck? If reverse works then please see below (from a previous post).

Originally Posted by 1project2many

Lets see if we can answer a few questions by describing the original OD operation. The OD unit is a planetary gearset added to the back of a three speed transmission. Overdrive is electrically shifted using a combination of speed (governor switch) and throttle position (microswitch) based controls in combination with a freewheel clutch.

When starting from a stop, the driver accelerates normally. As the vehicle reaches the governor cut in speed, the governor contacts close applying power to the shift solenoid. The shift solenoid operates an engagement pawl which is also mechanically blocked from engaging overdrive. The overdrive shift is left in a state of "waiting" until throttle pressure is decreased slightly and the vehicle is not accelerating. When this condition is reached the freewheel clutch activates, the blocking mechanism releases the overdrive pawl, and overdrive engages.

When the driver needs additional acceleration the accelerator is pressed down. At some point the accelerator pedal will operate a switch which opens power to the shift solenoid. This removes spring pressure from the pawl but torque on the driveline due to acceleration prevents the shift from occurring. Again this sets up a "waiting" state. The completion of the shift is allowed by temporarily grounding the ignition coil and shutting off the engine. Once the shift is completed the ground circuit is opened and the engine will resume normal operation.

The freewheel clutch is required to allow shifting in and out of OD. Non-freewheeling operation is a special case. The freewheel clutch does not allow a reverse drive to be applied to the driveline, and it does not allow the rear axle to drive the engine. With normal operation and freewheel clutch operating, the engine and transmission are disconnected from the driveline when coasting, when reversing, and when going downhill. If you need engine braking you may pull the handle or cable to "lock out" the freewheel clutch. In the original configuration this opens a control switch and removes power from the shift solenoid which in turn disables the overdrive. When shifting into reverse the shift rail is designed to automatically move the freewheel clutch into lockout and will also open the lockout switch.

Your shift solenoid will have two terminals. One terminal connects to the solenoid winding to engage the solenoid. The other terminal connects to ground whenever the solenoid has engaged OD. Applying power to the windings will apply pressure to the overdrive pawl but it's possible that the shift will not complete unless transmission input and output shaft speeds are different.

Note that the BW overdrive was used in 6V and 12V vehicles. IMO you should do research to determine which solenoid is on your transmission before applying 12V for testing. This may help:
https://fifthaveinternetgarage.blogs...overdrive.html

Overdrive manual from Borg Warner in HTML covers most non-GM applications and has some test procedures:
http://www.oldcarmanualproject.com/m...rive/index.htm

Same manual in a single PDF:
http://www.oldwillysforum.com/forum/...riveManual.pdf

LOTS of BW overdrive tech:
https://fifthaveinternetgarage.blogs...tech-tips.html

https://fifthaveinternetgarage.blogs...overdrive.html

https://fifthaveinternetgarage.blogs...verdrives.html

Basic OD wiring diagram from BW:
https://fifthaveinternetgarage.blogs...ve-wiring.html

These days the transmissions are far more common than the electrical switches and controls originally used for semi-automatic operation of overdrive. In many cases people installing these transmissions opt not to duplicate OE wiring or to supplement OE wiring by providing full manual control of the OD solenoid. Full manual control allows engaging OD in all forward gears (never start out in 1st OD).

This paper talks about using OD in "split shift" mode:
http://www.potomacbird.com/pctc/Publ...s/bwwiring.pdf
Note that the wiring diagram is very hard to view in the above PDF.

Here is some discussion of "split shift" operation on an old F*rd site:
http://ford-mel-engine.com/viewtopic.php?t=1483

Additional information can be found by searching for BW R10, Borg Warner R10, Borg Warner R-10, Borg Warner R-11, and many other variations.