51 merc transmission help please

[51mercconvertible]

My father and I just put in a newly rebuilt 3 speed transmission with overdrive in his 51 merc with rebuilt clutch. When we finished he backed it out of the shop, drove it about 3/4 of a mile everything seemed ok. Went to turn around and it won't go into reverse and the overdrive doesn't work. I'm afraid it's something I did installing the transmission but don't see how it could be. We are both stumped on what it could be Any ideas what could be wrong. It's the transmission that came out of the car. We just took it out to have it rebuilt and to rebuild the clutch. He doesn't use the internet so I'm trying to get some idea to help us. Thanks

[expavr]

Originally Posted by 51mercconvertible

My father and I just put in a newly rebuilt 3 speed transmission with overdrive in his 51 merc with rebuilt clutch. When we finished he backed it out of the shop, drove it about 3/4 of a mile everything seemed ok. Went to turn around and it won't go into reverse and the overdrive doesn't work. I'm afraid it's something I did installing the transmission but don't see how it could be. We are both stumped on what it could be Any ideas what could be wrong. It's the transmission that came out of the car. We just took it out to have it rebuilt and to rebuild the clutch. He doesn't use the internet so I'm trying to get some idea to help us. Thanks

Is the Overdrive linkage under the dash hooked up to the O/D lever on the transmission? When you pull out the handle does the lever on the O/D tailshaft rotate? This could be the reason you can't engage reverse.

[rotorwrench]

expavr has a point there. When selecting reverse, the short lever on the trans actuates the fork for 1st /reverse and also a small lever inside pushes the lock out rod back to disengage the OD. If the lockout rod is jammed for some reason, then it wouldn't be able to go in reverse.

When you pull the lock out control under the dash, it actuates another lever on the OD unit that also pushes the lock out rod. If the cable pull is also jammed then a further investigation will have to happen to find out why the lock out control won't move. There are several things that could cause that but the tail assembly may have to be pulled to find the trouble.

If this is an early 51 trans, there may be a problem with the lock out switch. Also check the little cable operated lock out lever on the tail housing. If it isn't in the correct position, it could jam up the works. I hope you have a 49 to 51 Lincoln Mercury Overhaul Manual. All the details are in there for these units.

[51mercconvertible]

This is indeed an early 51 model. I don't know much about these mercs, I just did the removal and installation for him. I do understand the lockout cable in the vehicle, and where it goes to the transmission. The lever the lockout cable goes to on the transmission is for sure all the way back where it's supposed to go. But I am wondering if that cable is where the problem is. Is there a way to systematically by-pass anything step by step to figure it out, or does the transmission need to be pulled again to check things?

[40 Deluxe]

On an O/D trans, engaging reverse moves an internal rod that locks out overdrive, same as the knob under the dash. If "overdrive" is engaged electrically you cannot shift into reverse nor pull out the lockout knob. This could be caused by the governor wire shorting to ground or the points in the governor being stuck closed. Can you shift into reverse with the ignition off? If "overdrive" is engaged, the car will not move backward, even in neutral. This could also be caused by the solenoid pawl being stuck. It engages overdrive electrically, but uses a spring to disengage. So something could be binding internally. With ignition on, ground the governor wire. You can do this at the relay so you don't have to crawl under. This should power up the solenoid and you should hear a definite 'thunk'.
With ignition on and governor wire grounded, floor the accelerator to activate the kickdown. You should hear the solenoid release, then engage again when you let up on the pedal. (You can pull the distributor cap and bump the starter until the points are open so they don't burn with the switch being on during these tests.)
Shift linkage should be OK since the car backed out of the garage at first (unless something fell off on the test drive). If these electrical tests are OK, it's probably time to talk to the rebuilder about internal problems.

[40 Deluxe]

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Looks like rotorwrench replied while I was typing. Hopefully the two of us gave you some insight!

[51mercconvertible]

Thanks so much for the responses. After reading them I believe it may be stuck in overdrive as when he came back we drove it up on ramps to look at it. Since it wouldn't go in reverse we tried to push it off the ramps. The two of us couldn't push it off the ramps backwards ( slightly up hill) and it seemed like it was in gear even though it was in neutral. We had to pull it off the ramps with the tractor. I watched the rear wheels and they did turn so I didn't think too much about it. Being locked in overdrive seems to make sense, now if we can figure out how or why. He is going to try the tests listed here. Thanks

[rotorwrench]

Definitely check all you can before going to the removal stage. 40 Deluxe has a point about the pawl position. It has to be out of overdrive before the lock out rod can move since there is a half moon cut in the side of it where the rod locks it. Cutting power to the system should let the main solenoid drop out which should pull the pawl with it. The solenoid has a ball shaped end on the actuator rod that engages the pawl so you can replace the solenoid easily. The only other thing I can think of would be if the sun gear is jammed up on the splines or gears so that it can't shift forward or aft far enough.

[expavr]

Originally Posted by 51mercconvertible

This is indeed an early 51 model. I don't know much about these mercs, I just did the removal and installation for him. I do understand the lockout cable in the vehicle, and where it goes to the transmission. The lever the lockout cable goes to on the transmission is for sure all the way back where it's supposed to go. But I am wondering if that cable is where the problem is. Is there a way to systematically by-pass anything step by step to figure it out, or does the transmission need to be pulled again to check things?

When you say"back" do you mean the orientation of the lever? When the O/D lockout is engaged the lever on the O/D tailshaft should be oriented towards the "front" of the transmission not the "back" of the transmission. Also, is the braided part of the cable anchored to the transmission housing with the anchor bracket that is located on the main housing between the shift arms?

[51mercconvertible]

I got a message that he found the problem but haven't heard what it was. I'll post what I find out. Thanks to all of you

[40 Deluxe]

Originally Posted by 51mercconvertible

Thanks so much for the responses. After reading them I believe it may be stuck in overdrive as when he came back we drove it up on ramps to look at it. Since it wouldn't go in reverse we tried to push it off the ramps. The two of us couldn't push it off the ramps backwards ( slightly up hill) and it seemed like it was in gear even though it was in neutral. We had to pull it off the ramps with the tractor. I watched the rear wheels and they did turn so I didn't think too much about it. Being locked in overdrive seems to make sense, now if we can figure out how or why. He is going to try the tests listed here. Thanks

Dragging it backward with a tractor can't be good!

[51mercconvertible]

It was the solenoid. All is working great now. Thanks for the help