1950 Car Transmission OD and Regular Length?

[leon bee]

I googled this and read my green book, can't figure it out for sure. Are they built so that an overdrive trans and a non-overdrive fit right in the same car without any modification? And use the same drive shaft? It looks to me like that was the plan.

I'm doing a 50 Coupe that I want to drive a lot, drive it from here on out. Two days ago went to the DMV, created paperwork and walked out with a tag! So we went for our first legal drive. I've put about 50 miles on it previously up and down the road out front of my shop, everything real good. Now I get a tag, and then the trans starts making racket. Seems like maybe TO bearing/clutch sort of noise. But now I really want a backup (spare) transmission. Thanks!

[Mac VP]

The regular 3 speed transmission and the overdrive transmission are both the same length for any specific Ford model year. The 1949-50 Ford passenger overdrive transmissions are identical. The 1951 Ford overdrive trans is nearly identical and is often swapped in on 49-50 Ford cars.....the main difference is a small move in location of the rear support pad (and a small change in the bolt hole spread of that mount). This can be fixed with a simple adapter plate.

The same features described above apply to the regular standard 3 speed transmissions.

Overdrive transmissions for 1949-50 Ford convertibles have special adapters for the mounting of the solenoid in order to clear the frame structure on the ‘verts.

[Frank Miller]

The transmission mount is put in backwards when going from one to the other.

[leon bee]

Thanks, guys.

[Ken Henry]

Here is a related question I have always wondered about: The 51 OD transmission does not have an electrical lockout switch on it for when the OD handle is pulled out, while the 49/50 design does. Consequently, on the 51, wouldn't the relay continue to energize at the cutoff speed and try to engage the OD solenoid? I realize the solenoid is prevented mechanically from engaging, but wouldn't the whole operation be hard on the electrical system? My understanding is that the solenoid draws the most amps when it tries to engage?


I have a 49/50 OD trans in my 51 presently (a leaker), and a spare 51 trans I'd like to rebuild and use, but have been hesitating due to the lack of the electrical lockout switch... Ken

[40cpe]

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I can't explain how it works like it does. Try running your speed to and above the engage speed but don't lift your foot to allow it to engage. Watch your ammeter dip as the solenoid is energized and then recover into charging territory. On the other hand, if the solenoid or wiring is faulty the ammeter will show a discharge and not recover until the relay is de-energized. I agree that the lock out switch is desirable, but as long as the solenoid operates correctly there doesn't seem to be a problem. Maybe switch your present OD housing to the rebuilt transmission.

[leon bee]

This is covered in that little overdrive booklet, which of course I don't have here. But I was thinking that lockout switch was something to do with reverse gear.

[Jersey Devil]

Lock out switch operated when in reverse. It opened the circuit so that the governor could not energize the solenoid while in reverse. Considering the governor only operated at or near 27 mph doing such while in reverse probably never happened. It was a safety device that was overkill.

Lockout switch was eliminated in 51 Fords. Switch became a source of trouble since normal operation of the circuit was thru normal closed contacts of the lockout switch.

Hope this helps,

Tom

[rotorwrench]

The lockout works not only in reverse but any time the lockout cable is pulled. When driving the car in the locked out position, the solenoid and relay are still active even if they can't function so it draws current for no reason. Borg Warner used the switch to prevent this but manufacturers likely felt it was redundant since most owners don't lock out the overdrive very often. Folks in Colorado for example, would lock there overdrive out to climb and descend mountain passes so it would be a good thing to have in that case but flatlander's likely only lock out the overdrive when towing a big trailer. In either case, I prefer to have the lock out switch so it doesn't tax the 30 to 35 amp electrical system if it doesn't have to. Both of my early 1951 Mercury cars still had the lock out switch but those switches are getting harder to source these days. A person could use an on/off switch if they want to be able to control the circuit with no lock out switch. You just have to remember it's there and when to use it.

[Ken Henry]

Thanks for the responses. My ammeter is a little lazy so it's hard to see how much current is drawn during OD engagement. Maybe some kind of external switch could be fitted to the 51 overdrive, that makes contact with the lockout lever and breaks the circuit when locked out... Ken

[40cpe]

Originally Posted by Ken Henry

Maybe some kind of external switch could be fitted to the 51 overdrive, that makes contact with the lockout lever and breaks the circuit when locked out... Ken

A simple toggle switch under the dash would suffice, as rotorwrench suggested. But a mechanical brake light switch adjusted to operate off the transmission end of the lock out cable should be simple enough to fab.

[Jersey Devil]

Ken

This is becoming “much about nothin”. The lockout switch in most cases was strapped out to provide circuit continuity because the switch was a source of trouble. If you gave a trans without the switch then the governor is wired directly to the kick down switch if you are using standard OD wiring.

Install the OD and enjoy.

Hope this helps,

Tom

[Jersey Devil]

Ken

This is becoming “much about nothin”. The lockout switch in most cases was strapped out to provide circuit continuity because the switch was a source of trouble. If you gave a trans without the switch then the governor is wired directly to the kick down switch if you are using standard OD wiring.

Install the OD and enjoy.

Hope this helps,

Tom

[Frank Miller]

There was never a replacement switch offered. Ford just said, It it does not work remove it from the circuit.