51 OD transmission question

Kdancy

 I have read that you need to put the OD out if you are going to back up.

If the cable is left in the "in" position, what can be damaged?

Jon B

Speaking only for myself, I never pull the knob out when backing up.  I think there's some sort of internal pushrod that does whatever needs to be done, whenever you throw the car into reverse. 

However, my OD is a 1940, which has a number of differences from the 1941 and up OD transmissions.

Toddh

The OD has both electrical and mechanical protection to keep the car from going into reverse while OD is engaged.  The internal mechanical linkage won’t allow you to shift into reverse and The governor won’t allow the OD to kick in until 22 mph. I’ve never had to pull the OD lever out to go in reverse.  I have both a R9-B1 and an R10 OD

Kdancy

ok, just found this-

https://vintageautogarage.com/blog/troubleshooting-the-borg-warner-overdrive-in-a-classic-car/

"The final thing to avoid that can immediately damage the overdrive is to reverse or start in first gear while overdrive is engaged. This will instantly crush the needle bearings inside the sun gear and require a several hundred dollar repair.

Fortunately, this mistake is only possible if you bypass electrical circuits by connecting the solenoid to the overdrive toggle switch, removing the kick down switch, relay, and governor from the circuit. This is not a factory installation, but some car owners have done this over the years, and most end up later paying the repair cost as a result."

Toddh

Well the website statement you posted may be true for first gear with those electrical conditions stated but It’s still impossible mechanically to engage reverse on the Hudson versions (I can only speak to the R9 and R10), even if you bypassed the electrical.  Not all versions of the BW OD’s are the same.  Take a look at the Packard version vs the Hudson version.  Both are R9’s but differently laid out.  They don’t interchange. 

Look. I’ve been driving my 46 R9-B1 for years and never once disengaged the OD with the cable. 

Toddh

So Mr. Dancy.  What prompts your inquiry?

cheyenne7271

You can leave the OD cable all the time. When you put the car in reverse the OD gets mechanically locked out. A caution though is when parking, if the car rolls forward in gear that will damage the OD unit. The car will hold if the car is uphill. Best practice is to disengage the OD when parking on an incline. 

Geoff

There are other factors to take into account.  My  '53 Hornet will engage reverse alright with the  knob pushed in, but the car will not do anything, because it has the wrong   selector shaft ( from a non o.d transmission,) so the overdrive is not disengaged.   When I let the clutch out  all that happens is the  free wheeling rollers turn.   So I have to manually pull the knob out if I want to go backwards.   Slightly inconvenient, but much easier than removing the transmission and overdrive and replacing the  shaft.   

Toddh

Cheyenne.  That makes no sense because the OD is only engaged when the solenoid pushes the pawl in.  And that only occurs when you reach 22 mph.  

Please explain how you determine this?

Toddh

It just goes to show you that modifying a working design will get you in trouble. 

cheyenne7271

Todd I meant when the OD knob is pushed in. 

cheyenne7271

Yiu can leave it push it all the time, even when parking, just set the brake so the car can’t roll forward. That will damage the OD unit. Otherwise when shifting to reverse mechanically the OD gets kicked out by design.