1951 Mercury Overdrive

Tommy Gun

Tommy Gun

Member
Hello,

I've read some threads on here and revisited Randy Rundle's Overdrive book and website, but am still having an issue I can't figure out.

My issue occurs after driving and using the overdrive. When I then try to shift into reverse, it won't go into gear. The Overdrive dash lever also gets stuck in (pushed in).

If I shut off the car and rock it back and forth it seems to temporarily fix the problem.

It seams like the problem happens after things warm up, but that may just be an illusion.

Reverse always works after a cold start and backing out of the garage.

Does anyone have any thoughts?

Thanks!
 
Hmm, when it won’t go into reverse, is the overdrive still engaged? For example if you put in first gear and try to pull away does it feel like second gear?
 
In which case you might have a sticking governor. You might try disconnecting the governor at the relay (Th SW terminal) next time this happens and see if you can then access reverse. Ken


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The transmission has a reverse lockout feature. It's internal to the trans and part of the shift cover. It has a little lever that pushes back on the shift rail to lock it out, Someone may have taken the cover off and replaced it with a standard transmission shift cover or it's missing some mechanical parts. The parts may be sticky or damaged as well. DO NOT try to use reverse until this problem is fixed. If you spray enough penetrant on the lock out cable then you can lock it out that way and run like a standard transmission till fixed. If the cable is fried then a person would have to get under the car and disconnect the cable then hard wire the lock out lever to the locked out position.

The Ford-BW OD transmissions will not work in reverse unless the OD is locked out. The free wheeling unit is in play anytime the transmission is in overdrive mode so it just free wheels in reverse but another thing that happens is that the balk ring gets out of place and pushing the car is the easiest way to get it back in place but sometimes it's tricky to get it working again.
 
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OK here we go. The pawl or dog or plunger( I've heard it called all three) that the solenoid pushes in is not retracting. Until it does no revers. Reasons for this, weak spring in the solenoid, worn pawl or lack of oil in the transmission. I hope its your solenoid, it's the easiest. Tim
 
Ok, thanks guys! That's a lot of good info. I'll start trying and see what happens.

One other thing, When I drive in standard 3 speed (no overdrive and dash lever pulled out) the handle will gradually pull itself all the way in to where in puts itself into overdrive mode. I will routinely pull it out at stops if I just want to stay in normal 3 speed mode. Hope that makes sense.

Could that be related to my issue?

Also, my car is converted to 12 volt with a '56 Ford solenoid. I followed all the Randy Rundle advise.
 
It's spring loaded but usually not that much tension. It usually stays where you put it. Some cables will lock with a half turn of the handle but there's usually enough friction in the cable to hold it.

A person can make a tool with tip like the tip of the solenoid rod to put into the pawl and manually pull it in and out. It should move smoothly. The pawl will not go all the way in until the balk ring turns enough to align the notch. A person has to let off the throttle to get that function when moving down the road at any speed above governor on speed.
 
Ok, here's a quick update: I tested the solenoid on the car and it sounded like it engaged. I took it out to make sure the seal was good and that there was no fluid inside.....All good there. Also, the trans and overdrive unit have plenty of fluid in them.

My problem is as Ken Henry describes above. It won't go into revers gear when the OD is engaged. Also, if I put in 1st gear, it definitely feels like it is 2nd gear. The OD dash lever will also be stuck in at this time. If I shut the car off and manually rock the car back and forth from the outside, it seems to reset and fixes the problem.

I hope to put in more time Sunday with some testing on the governor.
 
Sad to say but since you have to rock it to get it to drop out and the return spring is good on the noid it's not electrical. Something is physically binding the pawl in the OD unit. It's time to pull and inspect it before something really bad happens. Tim
 
The switch was used to open the solenoid circuit while the lock out rail is all the way back and locked out. It saves the electrical load on the system when the cable is pulled out. Ford considered it redundant in early 1951 and it was obsoleted. The lock out switch was vulnerable to the elements and it could be problematic. A lot of folks bypassed the switch rather than repair or replace it.
 
When you turn the ignition on do you hear a click from the trans? Cus it sounds like the solenoid is (in overdrive engaged state) from your description. You could whip the fuse out of the overdrive relay to cut power to the solenoid and test drive with the overdrive cable pulled out and see if it works like a standard three speed.
Martin.
 
Easter test.
Sorry been on the cyder. Turn ignition on and pull the fuse. You may hear the solenoid click out. If it does, looks like we're getting it. Could be as simple as a stuck or shorted relay. Fingers crossed.
Can't spell solenoid? Solinoid? Whitch won?
Martin.
 
rotorwrench said:
The switch was used to open the solenoid circuit while the lock out rail is all the way back and locked out. It saves the electrical load on the system when the cable is pulled out. Ford considered it redundant in early 1951 and it was obsoleted. The lock out switch was vulnerable to the elements and it could be problematic. A lot of folks bypassed the switch rather than repair or replace it.
Click to expand...

Yes, I bypassed the switch on my '50 Ford coupe. Didn't realize it was obsoleted by '51. Thanks for setting the record straight.
 
My unmolested, stock early '51 Mercury has the lock out switch, and it is still working. It also has the early ( '49-'50 style trans )
 
My 51s are both prior to the change over to the new transmission and bell housing so they have the switch. I have spares so I still run them. The new transmission looked a lot like the Ford car units but it had the new diamond cut gears and the big cast iron bell. I think the change was in February of 51. My cars are both November 1950 cars from the St Louis plant.

I'd test the solenoid function on the bench and make sure there are no wire to wire cross shorts. The wiring couldn't be in a worse place for weather contamination. The problem with a welded relay contactor is that it can't be dropped out of overdrive and the solenoid would be energized all the time. The relay is farely easy to test.

If that solenoid is engaging when the key is turned on then there is a problem with it, the governor, the relay, or the wiring. It shouldn't be able to do that. When the pawl loads against the balk ring then it may not allow the shift rail to move. The solenoid has to drop out of overdrive to pull the handle and lock it out when on the move. A person has to floor the throttle pedal to drop it out. The kick down switch provides that function.
 
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Scooder might be on to something....I started with turning the ignition on and off and nothing happened with the solenoid. A short time later, I would turn the ignition on and off and the solenoid engaged/disengaged with the ignition. Huh?

I checked the relay and all is good. It clicks and has continuity when engaged. All connections looks good.

Now, the solenoid won't engage/disengage with the ignition.

I do notice that the shifter knob and arms move smoother after that solenoid manipulation. Perhaps something was still partially engaged causing the shifting to be less smooth....now it's smooth?

Note: I was just messing with the shifter in the garage while the car's on jacks. I haven't driven it.
 
Governor has weights and a central plunger that moves in and out. I have never seen this but it could be jamming/sticking in ‘on’ position
 
If the relay checks good then that leaves the kick down switch and the governor to check. I'd look at the wiring on that kick down switch real close. The power wiring for the solenoid could cross short if the wires are close together anywhere and insulation is on the deteriorated side.
 
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