Disengaging OverDrive

[ThriftyT]

‘40 Chrysler C25.  No matter what I try, I cannot pull the car out of overdrive while the car is moving, without it grinding.     Are you able to? Or am I doing something wrong?    Thank you in advance 

[Dodgeb4ya]

Have you tried it at 23 MPH or less with foot lightly on the throttle....not coasting?

Have you also tried pulling it out of OD with it kicked down...throttle to the

floor ?

But probably reading the owners manual or shop manual would be a good place to look first.

[ThriftyT]

No I haven’t.   Will give it a try

[greg g]

Are you talking about actual of engage, disengage through the relay governor circuit, or when pushing in the control cable?

[ThriftyT]

Pushing in the cable.   , I  did it once today.  Tried 2 more times and couldn’t.  Need to figure out what I did the 1st time. 

[martybose]

It sounds to me that you are trying to shift the mechanical control (not sure if it is a lever or a control cable in your case).  If so, that is a definite no-no.  On the later ones the manual specifically states that you shouldn't pull the control cable out unless you are at a complete stop.  This engages a pawl into a square cut gear, and doesn't go in well if it is moving.  You need to find out how to do an electrical downshift, which is very different.

 

Marty

[ThriftyT]

Thanks.  I will do some more research 

[Dodgeb4ya]

If there is any grinding....you better stop.

Read the book...as that trans will be very hard to find parts for and costly!

For the time being...I'd pull it out...push it in at stops only until you know for sure how/ and when the lockout cable can be moved.

That's typically how they were operated anyway.

1953 and later  R10 OD's can be pulled in and out easily with out harm doing it right.

The owners manuals describe how to do it.

 

[greg g]

I have mine wired through a push pull switch. The switch controls the OD relay switch side from the ACC terminal of the ign switch. So if 

I am just bombing around town, I leave to cable out and switch off. If I decide to extend the jaunt I will push in the control cable at a stop light. Then when on the open road, pull out the switch to engage the OD through the relay according to the governor's operating perimeters.just be aware the with the cable in the OD freewheels below 30 mph so compression braking goes away. Kinda like driving an old 2 stroke SAAB...

[Go Fleiter]

I have a type 2 OD and provided a toggle switch to unpower the OD Relais.

to engage the OD engine should be uncoupled, pushing the clutch

to disengage the engine should be pulling thus pushing the gas pedal a moment.

(warning: sorry, I didn´t drive for a coulpe of weeks, I hope my memory doesn´t fool me...)

At first,  I had left the appropriate cable and handle off,

but the free wheeling at lower speed disturbed me too much.

btw. I didn´t install the kick- down switch. It´s crude function does not seem appropriate for

such an old car.

 

(all speeds are speedometer radings! GPS: take 10% off)

Edited May 24, 2020 by Go Fleiter

[Loren]

My experience is with the B-W R 10 Overdrive from the 1950s & 60s.

The cable is used to block out the Overdrive from engaging. It should only be moved while the car is stationary. And the only reason for its existence is the freewheel sprag clutch in the Overdrive. Without locking the Overdrive in direct drive (pulling the cable) parking the car in gear does not prevent it from rolling. Best to use the parking brake when you have an Overdrive.

Next one of my pet peeves is not using the Overdrive wiring as designed. The Throttle Switch and Relay are vital to keeping your (now days) very expensive Overdrive in good shape. The governor is wired to signal the solenoid to shift the Overdrive (both up and down) the relay connects not only the throttle switch (for kick down) but (and this is the important part) the ignition coil to momentarily interrupt it thus releasing torque on the driveline. The interruption is so slight that the driver never notices it, but the Overdrive does and that keeps it happy.

The Laycock de Normanville Overdrives on foreign cars had a switch which engaged it but no ignition interruption feature. So you had to use the clutch or endure one hell of a clunk with the attendant mechanical anguish. They were not "automatic" like the B-W.

When wired and used as designed the B-W R 10 is a real joy to drive.

First gear in a three speed is just to get you moving, second was intended for town driving 25-30 mph. High gear was for the open road around 55 mph. Final drive gear ratios were chosen based on this type of operation. When the Interstate Highway System was being built during the Eisenhower Administration the days of the 3 speed transmission and 4.11 gears were numbered. To reduce engine speeds and still provide good performance meant either a 4 speed with a lower numerical final drive ratio or an Automatic Overdrive. 4 speed transmissions were more commonly seen in trucks and they had a reputation for being awful. It was thought drivers would not buy them. An Automatic Overdrive didn't require shifting one more time and the same final drive ratio could be used. In a 3 speed or a 4 speed of the time high gear was direct drive. An overdrive top gear had to wait for the 5 speed transmission.

Unfortunately for us in the 21st century the Overdrive transmission is still connected to non-synchro first gear three speeds. 70 mph highway speeds are just not obtainable with 4.1 gears even with an Overdrive. So we change the final drive ratio to something like a 3.73 or even lower (with an axle swap). Now first gear becomes a lot more important because you've got a real mountain to climb. That's why the B-W T-5 has become so popular, they are cheap and readily available. However, I can't bring myself to cut a hole in the floor of my car for a shifter, so I have an Overdrive.

[Young Ed]

16 hours ago, Loren said:

My experience is with the B-W R 10 Overdrive from the 1950s & 60s.

The cable is used to block out the Overdrive from engaging. It should only be moved while the car is stationary. 

 

Only pulled (disengaged) while stationary. You can engage at speed.

[Dodgeb4ya]

You can also easily pull the cable out above  cut in speed on a R10 by a full throttle kick down....as soon as the trans kicks out of OD pull the handle out.

This on only factory installations.

I cannot recommend this on non stock as I don't know how owners have controls set up.

Push the handle in at any speed...just don't be coasting....foot lightly on the gas pedal.

Edited May 25, 2020 by Dodgeb4ya

[Loren]

Yes you CAN do just about anything.

The question always is SHOULD you do it?

The answer is not in my car.

[Dodgeb4ya]

Better read the factory OD instructions.

The handle pulls out very smooth done right.

Did it for years of daily driving and still do when I get my 52 Belvedere out.

Don't be scared....

An Imperial Airflow....no way.