[SEL] OT R-10 Borg Warner overdrive.

[Elden DuRand]

Curt:

You're now talkin' to a guy who's had several of the Borg Warner Overdrive units in various cars.

To answer your questions, when the Overdrive is locked out via the dash cable, it acts like a regular stick shift in all ways.

Definition of "lock-out":  When the Overdrive gearbox is locked out, the sun gear is locked to the outer ring gear by shifting the sun gear so teeth in it engage with inside teeth in the planetary gear carrier.

When the dash cable is pushed in, the transmission free-wheels in all three gears except reverse.  When the transmission is put into reverse, a pushrod from the reverse shift fork forces the Overdrive to lock-out, otherwise, the transmission would lock-up when you tried to reverse and could damage the sprag clutch or planetary gearset.

When the engagement solenoid is actuated, a pawl in conjunction with the sprag (one-way) clutch causes the sun gear to be held stationary while power from the engine is transmitted to the gear cage.  When the engagement solenoid is not actuated and the Overdrive is -not- locked out, power is transmitted from the sun gear and the cage to the ring gear, giving a 1:1 ratio.

THERE IS NO FREE-WHEELING WHEN EITHER THE O/D IS LOCKED OUT OR IS NOT LOCKED OUT AND THE SOLENOID IS ENGAGED.  Years ago, "free-wheeling" was touted by, I think, Chevrolet, as being an economy move.  It actually was a danger because the engine could not brake the car and, going down hills required riding the brakes, heating them up and causing them to fade.

There are a couple of other things that you should understand about the electrics of the Overdrive system.   There is a governor that actuates a relay which, in turn, powers the Overdrive solenoid.  The solenoid has two coils inside with a set of contacts that shifts beween a high-power coil when the plunger is in the disengaged state and a lower power coil which holds the solenoid plunger bottomed with less current when it is engaged.

There is also a "kick-down" button underneath the gas pedal that has a form-c contact arrangement.  The normally closed contact is in series with the ground line to the relay coil.  When you floor the accelerator, the pedal actuates the switch and releases the solenoid by interrupting ground to the relay coil.  

You will note that there is a second contact inside the governor which goes to the second solenoid wire.  This contact closes a circuit to ground when the solenoid is energized and grounds the ignition points to kill engine power for a very short interval to release the load on the Overdrive pawl, allowing it to retract.  Once the pawl has retracted, power is restored.  

If the system's working right, above about 30 mph (depending on the speed at which the governor powers the relay) and with the dash cable pushed in, the overdrive can be engaged by letting off the gas and allowing the higher gear to engage.  You can feel the shudder when the pawl engages and then can re-apply power.

When you need the lower (non-Overdrive) gear while cruising (and above governed speed), simply floor the accelerator and you will then be in "passing gear".  Once you've finished passing, simply let off the gas and let the Overdrive re-engage.

Rule:  Do NOT pull out the Overdrive dash knob while free-wheeling!  This will cause a very irritating and not-too healthy grind of the sun gear with the internal gear on the gear cage.  If you must lock out the Overdrive while moving, pull the dash knob out only after flooring the accelerator (kicking down the transmission) while power is applied.

In conclusion, I've driven several hundred thousand miles with Overdrive transmissions.  When used properly, they are reliable and long lasting.  In fact, Overdrive extensions were used on Chevys up to the 1960's.

Note that the Overdrive option was really nice when friends in the '50's went to the drags with their Detroit iron.  Most Overdrive cars had 4.11:1 rear axles and could really scat in a drag race and, with the Overdrive in the car, they were legal under stock rules.  Simply lock out the O/D and beat the competition.

I added a little feature in my '54 Ford.  I put a switch on the dash that allowed me to engage the O/D at a stop and pull out with an extra high set of three speed gears (like a two speed axle).  One of the things we did in my teens was to play "low gear chicken" (for the lack of a better term).  Two cars would line up and take off in low gear.  The point was not to get somewhere first but to see who had either the engine or the nerve to go fastest in low gear.  There were more than a couple of '55 (283) Chevy drivers that were embarrassed to be outclassed by a measly 239 Ford.  That thing would do almost 60 in low gear!  :-)

Take care - Elden
http://www.oldengine.org/members/durand 

> -----Original Message-----
> From: sel-bounces at lists.stationary-engine.com
> [mailto:sel-bounces at lists.stationary-engine.com]On
>  Behalf Of
> curt at rustyiron.com
> Sent: Monday, December 29, 2008 05:00 PM
> To: stationary-engine at oldengine.org; 
> sel at lists.stationary-engine.com
> Subject: [SEL] OT R-10 Borg Warner overdrive.
> 
> 
> Off topic, but hopefully a few mechanics out 
> there can confirm something
> for me.
> Working on the Willis transmissions. There is a 3 
> speed T-96 standard
> transmission with the Borg Warner 2 speed R10 
> electric operated
> transmission on the back. I've got it all back 
> together and am shifting it
> and checking out the OD functions on the bench.
> With the OD solenoid activated I am seeing that 
> the freewheeling action is
> disabled AND I am seeing that the output shaft 
> won't rotate in the
> backward direction. Does this all sound correct?
> 
> Freewheeling works with the solenoid off in all 3 
> forward gears. Since the
> OD tranny's purpose is to promote fuel economy, I 
> expected freewheeling in
> the OD mode as well. Imagine my surprise. So 
> that's why I'm checking to
> see if anyone knows.
> 
> The lack of rolling backwards was a bit of a 
> surprise too. The books all
> tell you that if the pawl hangs up and won't 
> release the OD, you'll not be
> able to get the vehicle in reverse, nor will you 
> be able to roll it
> backwards. With a little additional wiring, one 
> could configure the
> vehicle to be self holding on steep hills for 
> inexperienced clutch
> users/drivers.
> 
> Thanks for any guidance anyone has.
> Curt Holland