[SEL] OT R-10 Borg Warner overdrive.

curt at rustyiron.com curt at rustyiron.com
Wed Dec 31 13:55:29 PST 2008


> 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.

Agree.
>
> 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.

Agree. The sun gear is shifted aft to engage with the outer ring. Same
thing happens when shifting into reverse with the front transmission.
>
> 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.

I'm not observing this. What I see is that the one way clutch with the 12
rollers aft of the planetary gears will not transfer reverse rotation. In
order to actually get reverse rotation of the output shaft, the sun gear
has to be locked to the ring gear. I'm not seeing any lock up conditions
you mention.

>
> 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.

Agree.
  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.

Agree.
>
> THERE IS NO FREE-WHEELING WHEN EITHER THE O/D IS LOCKED OUT OR IS NOT
> LOCKED OUT AND THE SOLENOID IS ENGAGED.

OK that answers one of my questions. There is not supposed to be free
wheeling when the O/D solenoid is engaged. Seems counter intuitive to the
fuel economics they were trying to achieve with O/D! Especially when you
consider that free-wheeling only existed from 0 thru about 27 mph before
the centrifugal switch pulled in.

 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.
But you had engine braking as long as you were in O/D, right? So it was
only dangerous at speeds under 27 mpg with the cable pushed in, right?
>
> 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.

Yup, got all that working.

 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.

Yup, got all this working too. Pulls 3 amps when 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.

Yup, got all this up to snuff too.
>
> You will note that there is a second contact inside the governor which
> goes to the second solenoid wire.

Got this working as well.

  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!

Thanks for the heads up. Had not thought of this!

 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.

This Willis has a 5.33 ratio rear end. Devin better not be drag racing
this vehicle! He won't stand much of a chance with a 4 cylinder making a
mere 73 HP! We are simply trying to get the O/D working so we might have a
chance of going more than 45 mph!
>
> 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

We've done the same with the O/D switch on the dash for now, as we are
simply testing things out. We used the hole the lighter was in originally
and I turned a nice brass washer to adapt an aviation style switch to the
larger hole in the dash. The little switch has a green LED in the end to
tell you it is on. Teen boys think that is really kewl. Actually Missy
picked the switch out at the auto parts store. Would you expect any
different of a EE?

No one has answered the second question. I've got this transmission on my
bench. With the O/D solenoid engaged, will the output shaft lock up when
attempting to rotate in reverse? I think this has to be the case, because
running down the road in O/D the output shaft would be overrunning the
main shaft (coming out of the 3 speed transmission). When I try and
reverse the output shaft, the overrun clutch locks up and prevents
rotation thru the dog .

Elden, thanks for the detailed explanation. I'm trying to confirm
everything is as it should be before tightening all the bolts and
committing paint to the assembled transmission assy. I hate to screw up
fresh paint taking something back apart!

Curt






 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
>
>
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