Borg warner overdrive troubleshooting

Automotive Stud

Automotive Stud

Well-known member
I have a 1950 Merc overdrive behind my flathead. For now I have it wired with a toggle switch, but I can't get it to work. Currently the lockout handle is connected and works as it should, I have a new 12v solenoid from a Studebaker hooked up via a relay to a toggle switch, bypassing the governor, which seems to be engaging when I hit the switch. When the lockout handle is pushed in it freewheels at all speeds and engaging the toggle switch doesn't seem to change anything. Also with the solenoid turned off and after coming to a stop it is difficult to pull the overdrive lockout handle back out. I have a lot of literature on these overdrives but it is a little overwhelming, especially when most of the troubleshooting focuses on the original style wiring and switches. What should I look for first?
 
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Does one side of your toggle switch go to ground? The governor completes the ground circuit for the relay when the car hits 28 MPH, which energizes the solenoid, allowing overdrive to engage when you let off the gas. So when you turn your toggle switch on, you are grounding the relay to turn it on. You should hear the relay click when you turn on the toggle switch. If the relay 'clicks' on, check for power to the solenoid. If no power, it's likely a bad relay but make sure the fuse on the relay is good. Which solenoid wire is the relay connected to? One wire (usually red, if I recall) energizes the solenoid, the other is the momentary ignition ground for the kickdown. Use a fused jumper wire direct to the solenoid to see if it clicks.
By the way, why are you bypassing the governor? There should not be any need to do this except for troubleshooting. And, do you have the kickdown switch installed and properly adjusted? Again, there is no reason to not have the kickdown feature. This instant 'passing gear' is one of the best things about this style overdrive.
 
Yes the switch grounds the relay, and I can hear the solenoid click when the car is not running. I would like to verify the overdrive works before I complicate it further with the governor, which visually looks to be in questionable condition. I plan to revisit it after I know the overdrive works as it should.
 
OK. I was stating the obvious, but I have been known to overlook the obvious on occasion! Try energizing the solenoid while holding your hand on it to see if you can feel the plunger moving. There should be a definite 'thunk'. Also, are you sure the solenoid plunger is hooked into its slot inside the trans? (again, stating the obvious).
 
I don't mind revisiting the basics, I'm pretty new to these overdrives. I'm sure the plunger is hooked up, I had to twist it to install it and it basically held itself against the case while I ran the bolts in.
 
Automotive Stud said:
I don't mind revisiting the basics, I'm pretty new to these overdrives. I'm sure the plunger is hooked up, I had to twist it to install it and it basically held itself against the case while I ran the bolts in.
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OK, I'm running out of ideas for easy fixes. One more, does the lockout cable push the arm back far enough to allow overdrive engagement? I assume it does because it freewheels. I can't remember if there is an "inbetween" that both lets it freewheel yet prevents engagement.
 
The lockout mechanism is called the shift rail. It is spring loaded at the rear and is actuated either by pulling the cable or selecting reverse gear. There can sometimes be problems with the rail spring that don't allow it to properly shift. There can be problems with the operating pawl that is shifted by the big solenoid. There can be problems with the balk ring & plate that the pawl locks into.

Borg Warner designed in the safety mechanisms for a good reason. The first time you forget to turn off the solenoid when you come to a stop, it might get tricky to get going again. The governor switch makes sure this doesn't happen. The solenoid actually has two coils in it for shift in operation. One has heavy windings for a good solid push when engaging OD and the other is a holding coil with lighter windings to keep it from dropping out after it engages. All this stuff has to work or the OD will be problematic. The solenoid needs a fair amount of current to get it to engage. If your switching doesn't allow for that then it may not engage all the way.
 
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Both of the solenoid windings are in the same control circuit (there is only one power lead going to the solenoid). As soon as the solenoid armature (the plunger) moves toward engagement the pull-in coil's points open, leaving only the lower amperage holding coil hot. That feature should still operate no matter what electrical control device is used, the governor or a toggle switch. If the pull-in coil points are always open the holding coil must do the entire job (pull-in and holding) and may not be up to the task. One way to see this is to hook up an automotive clamp meter to the solenoid's power lead. The pull-in coil in good shape will pull in the neighborhood of 30 amps for an instant. If not then its points are likely always open. The holding coil operates at around 15 amps. Another and easier way is to remove the solenoid, remove the cap and pull the armature by hand while watching the pull-in points. They are about 1/2 way between the top of the solenoid and the base. They are normally closed until the solenoid is energized and the armature moves toward engagement. If you find them open you can adjust them. Conversely, if they remain closed all the time the continuous high amp draw will eventually burn out the windings and you'll be looking for a new solenoid.
 
rotorwrench said:
The lockout mechanism is called the shift rail. It is spring loaded at the rear and is actuated either by pulling the cable or selecting reverse gear. There can sometimes be problems with the rail spring that don't allow it to properly shift. There can be problems with the operating pawl that is shifted by the big solenoid. There can be problems with the balk ring & plate that the pawl locks into.
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I think we are getting somewhere here. I was reading and testing last night, it seems that perhaps the blocker ring has rotated. I found this from another thread on here.

Improper position of blocker ring:

1 - Occasionally, either in assembly at the factory or in service operation, the internal parts of the OD unit may have been rotated with the solenoid removed and the pawl withdrawn from its normal location. This may cause the blocker ring to rotate, so that its two lugs are not located with respect to the pawl. The solid portion of the blocker ring may be in alignement with the pawl, which will prevent full engagement of the pawl with the sun gear control plate.

2 - To test for this condition, remove solenoid cover, pull dash control knob out, roll the car 2 feet forward. Push dash control in, turn ignition switch on. Then, ground TH SW teminal of relay, and watch movement of center stem of solenoid. It should not move more than 1/8 in. when solenoid clicks.
Then, with the relay terminal still grounded, shift into low gear, and roll car forward by hand. Solenoid stem should then move an additional 3/8 in. as the pawl engages fully. These two tests indicate proper blocker action. Unless both tests are met, the blocker ring is probably not in the correct position.

3 - Rather than dissamble the entire OD unit, this condition may be corrected externally. With the transmission in neutral, and the dash control pulled out, move car forward one full turn of the propeller shaft. Then, loosen the two solenoid capscrews as far as possible, without removing and pull solenoid out as far as it will go, and hold it there while the propeller shaft is turned forward about 1/8 turn. Then push solenoid in and tighten capscrews.

When I did this it seems the solenoid pulls in about 1/4" but doesn't move when the driveshaft is rotated again. I tried step 3 several times but I didn't see any difference. I still have to road test it, I'm hoping I can fix it without dismantling the overdrive unit.
 
So I guess the question now is can I reposition the blocker ring without taking the overdrive off of the back of the transmission?
 
It should be possible to do this without disassembly but it might require pushing the vehicle around. The balk ring (blocker ring in previous post) is fitted to the gear plate by some sort of swaging method at manufacture. It has to have some resistance to rotation with the ring or it will always fall to its lowest position just by its own weight when you pull the pawl out. When this happens, the balk ring has to be moved back into position through the procedure that is in post 9 and this depends on the friction there as to whether it will stay with the gear plate as it rotates. If there is not enough friction then the transmission may have to come apart to replace the balk ring & gear plate assembly. The lack of friction will cause rough shifts and vehicle can not continue in service without experiencing more problems.

I've know two people over the years that have had a major lock up when driving down the road. Suffice it to say that this isn't an experience that either one of them ever wanted to repeat. One was due to a broken pawl and the other was a disintegration of the planet gears. The old Mercs are heavy and too many bang shifts will get to a person eventually.
 
I know it’s frustrating, but the o/d units are really worth the effort. I haven’t had one apart since the 70’s, but I got it back together as a 18 year who knew nothing. So stay after it, and if possible do the whole electrical set up. They work really well.

Something that doesn’t often come up is that they had a spring loaded link from the the bell crank to the carb, at least my 55 bird’s did. This let you go to wide open throttle just as the pedal contacted the kickdown switch. Pushing harder, the spring loaded link let the pedal actuate the kick down switch without overstressing the carb linkage. I think they’re hard to come by now, but if you’ve got an odd looking link, that’s what it is.
 
rotorwrench said:
It should be possible to do this without disassembly but it might require pushing the vehicle around. The balk ring (blocker ring in previous post) is fitted to the gear plate by some sort of swaging method at manufacture. It has to have some resistance to rotation with the ring or it will always fall to its lowest position just by its own weight when you pull the pawl out. When this happens, the balk ring has to be moved back into position through the procedure that is in post 9 and this depends on the friction there as to whether it will stay with the gear plate as it rotates. If there is not enough friction then the transmission may have to come apart to replace the balk ring & gear plate assembly. The lack of friction will cause rough shifts and vehicle can not continue in service without experiencing more problems.
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Humm, the transmission shifts great, so that sounds promising. I spent about an hour with the rear jacked up, spinning the driveshaft by hand and pulling the solenoid as described with it locked out of overdrive with no luck. It doesn't feel like pulling the solenoid is really pulling the pawl any further out. I'm debating trying that one more time or just pulling the tailshaft with it in the car after work one night. Hopefully I have enough room to do it in the car without removing the transmission.
 
You will need a lot of room to remove and install the OD tail housing. There isn't enough on the older 49/51 Mercs that I'm more familiar with so I always pull the whole transmission to work on any internal stuff. The planetary and the freewheeling unit take up a lot of housing depth. The free wheeling outer race, ring gear, and the OD main shaft come out with the tail housing but the rest stays on the transmission. I find it much easier to reinstall with the whole transmission tail end straight up. A rubber band is used to hold the free wheeling sprag rollers in place for this. Doing it horizontally could be difficult.

I also noticed that you are using a solenoid from a Studebaker. Most of the Solenoids used are the same but there are some different length ones for different applications. If it has the same shaft length when engaged & disengaged as the Mercury did then you are OK. Fifth Avenue Internet Garage has new ones but I've purchased some good ones from the flea-pay without breaking the bank. Folks run the 6-volt ones on 12-volt and most say they work OK but I haven't tried it myself.
 
I just installed a overdrive in my 50 a few weeks ago so this is of interest to me, lucky for me my trans worked correct from the start. I refilled mine with GL1 mineral oil, thats what the Borg-Warner book recommends, NAPA has it in one gallons. As far as the solenoid the one I'm running right now is a Delco, I picked it up from eBay. Mine uses a one inch shaft length, it sounds like yours should be the same. Did your lock out lever feel like it was spring loaded? I have a 53 trans that does not but the trans I'm using does. I noticed this with both units on the work bench comparing the two. On the one that doesn't i feel that something is seized. The new pull cable I installed requires a slight counterclockwise twist to move it in or out, the first time I tried it I thought something was wrong or binding. Just a thought, I wonder if you keep trying it will it free up, mine shifted hard the first few times but now its smooth going in overdrive.
 
rotorwrench said:
You will need a lot of room to remove and install the OD tail housing. There isn't enough on the older 49/51 Mercs that I'm more familiar with so I always pull the whole transmission to work on any internal stuff. The planetary and the freewheeling unit take up a lot of housing depth. The free wheeling outer race, ring gear, and the OD main shaft come out with the tail housing but the rest stays on the transmission. I find it much easier to reinstall with the whole transmission tail end straight up. A rubber band is used to hold the free wheeling sprag rollers in place for this. Doing it horizontally could be difficult.

I also noticed that you are using a solenoid from a Studebaker. Most of the Solenoids used are the same but there are some different length ones for different applications. If it has the same shaft length when engaged & disengaged as the Mercury did then you are OK. Fifth Avenue Internet Garage has new ones but I've purchased some good ones from the flea-pay without breaking the bank. Folks run the 6-volt ones on 12-volt and most say they work OK but I haven't tried it myself.
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Thanks, if need be I think I have the room to get the tailshaft off. I really don't want to pull the transmission again if I can avoid it. My new solenoid is 1" shaft same as the original.

Greg58 said:
I just installed a overdrive in my 50 a few weeks ago so this is of interest to me, lucky for me my trans worked correct from the start. I refilled mine with GL1 mineral oil, thats what the Borg-Warner book recommends, NAPA has it in one gallons. As far as the solenoid the one I'm running right now is a Delco, I picked it up from eBay. Mine uses a one inch shaft length, it sounds like yours should be the same. Did your lock out lever feel like it was spring loaded? I have a 53 trans that does not but the trans I'm using does. I noticed this with both units on the work bench comparing the two. On the one that doesn't i feel that something is seized. The new pull cable I installed requires a slight counterclockwise twist to move it in or out, the first time I tried it I thought something was wrong or binding. Just a thought, I wonder if you keep trying it will it free up, mine shifted hard the first few times but now its smooth going in overdrive.
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I put in Stalub I picked up locally that still meets the early specs. Yes, my control cable seems to assist itself to push it into overdrive, it just takes a light push of the cable and it goes right into the dash.
 
I haven't had a overdrive transmission apart but on all the others standing it with the input shaft down works well. In my younger day I kept a front case to use as a stand, I also had a hole in a wood table at a former job to stand a trans vertical.
 
Okay I was able to get it working without disassembly. Just turning the driveshaft while playing with the solenoid got it to go in. Now I have another problem, after a longer drive the overdrive would not disengage. Could someone explain the holding circuit in the solenoid to me? It seems my solenoid was stuck on, I had to pull it out of the transmission just to get it back into reverse. Also, it blew the fuse to the relay it is powered by.
 
The solenoid circuit is divided into 2 circuits inside the solenoid, the high amperage pull-in coil (30 amps) and the low amperage hold in coil (15 amps). Sounds like the pull-in points are out of adjustment, not opening to break the pull-in circuit. The pull-in points are normally held closed by spring pressure until the governor grounds the relay. At that point the high amperage overcomes the spring and "urges' the plunger toward the pawl. As soon as this movement starts the pull-in points should open, leaving only the lower amp hold-in points live. When you lift off the gas and the notch in the drive plate aligns with the pawl the plunger completes it's travel and the OD is engaged. The easiest way to test this is to remove the solenoid, remove the cap and pull the plunger by hand while watching the pull-in points, located about halfway down on the side. They should open as soon as the plunger begins to move. If not then you have the full 30 amps going to the solenoid all the time, blowing the fuse. Over time this can burn the windings inside the lower half of the solenoid, an unrepairable situation. You can adjust the points by shimming with small washers until you get the action correct.

I attached a file describing the adjustment. There are several different approaches, bending, shimming or whatever gets you there.
 

Attachments

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When the solenoid initially pushes the pawl, it stops against one of the steps in the balk ring. When you let off the throttle, the free wheeling action allows the balk ring to move into the engage position and the solenoid pushes the pawl on in to lock the ring plate for overdrive function. The solenoid has to be all the way engaged in order to change to the hold coil function. If it doesn't engage the pawl all the way into the ring plate slot, it will not change over to the hold coil.


The 49 thru early 51 Mercury transmissions have an interlock spring that acts on the pawl. There may be a problem with that spring set up. There are two different lengths for that part. It sort of sounds like something is still blocking the pawl movement so I'm wondering about that possibility.


In any case, the solenoid should drop out when the power is cut to it. Generally, the power is cut by the governor when you decrease speed below 26 MPH. It will also drop out when you hit the kick down switch. If it isn't dropping out in off mode then it's either a solenoid problem or a pawl problem. A stuck relay might not let the solenoid drop out so add that to the list too.
 
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