Borg Warner overdrive solenoid

[Britcheflee]

Hello, I am a new member and whilst searching for help via google realized that there are a lot of very knowledgeable people here who may be able to help with an issue I have with my overdrive.
I have a 1953 Mercury with the BW overdrive which has been mentioned in previous posts I have the same issue as Fred in France had: I have re-wired everything and confirmed all works - however, since re-wiring and activating the solenoid both by grounding TH post on relay and by direct power to post on solenoid (both working) I cannot get it to ground and briefly stop the motor either stationary or whilst driving. The switch is new and I have confirmed that I get continuity across the two posts when it is pressed in - I have also used a wire to ground the wire from the coil on the switch posts and it briefly stops the motor. So, somehow what is supposed to ground in that solenoid is not grounding. Not sure what to do now. I would like to take that solenoid off the transmission whilst it is up on blocks but concerned about how difficult it is to re-install - does it just pop right back in?
Also at the back bottom of the separate section of the transmission where the OD system is I see a small thing which can only be described as a rubber bung - is this the drain hole for the OD section? I have posted a pic pointing at that bung/drain hole thing.
Finally, am I fussing over nothing - just how noticable is the overdrive when it is engaged/disengaged? I dont feel any change in power, rpm or anything when driving along but it might be so slight not to be aware of it.
LOTs of questions sorry hopefully some info from you guys can help me out.
Lee

[Ross F-1]

There should be a very noticeable change in RPM -- 30% -- when OD is engaged. I suspect you aren't getting it into OD.

[Dobie Gillis]

Not sure what the rubber bung is for, never seen one before. It's possible your trans came out of some other make since B-W sold them to several different manufacturers. To drain the trans and OD just remove the drain plug on the main trans; there is a passage between the OD section and the main box. Does it shift into OD when you lift off the gas above about 27 mph? The kickdown to direct drive should be noticeable but it's not the kick in the butt you get when hitting passing gear with an automatic.

[Britcheflee]

I agree, I dont think its going into overdrive. I checked the engage/disengage lever under the dash and its moving the lever back and forth as expected - however, is there a way to tell if its engaging or not? I can make the solenoid engage and disengage by grounding the system and I can hear the thing clicking when I slow down as I assume governer drops below 28 mph and it disengages. But, I just have this suspicion that its not working - Ill take it over to a guy who works on these old cars next week and take him for a drive see what he thinks. I read that the two compartments were separate and they need filling separately but good to hear that they are connected as I never checked oil in there.

[Dobie Gillis]

If it's working you should hear the solenoid click under the car when you reach 27 to 28 mph. Lift your foot off the gas and it should shift into OD, usually with a slight lurch. It should disengage automatically when your speed drops below about 21 mph, not 28. As long as you keep your foot off the gas it will freewheel down to 5 or so mph until the OD input and output shaft speeds match. You will need to hit the clutch at that point if you're stopping. If you can hear the solenoid clicking it means the governor is grounding or de-grounding the relay as it should. You do need to lift off the gas to make it shift up unlike the Laycock OD found in many older British cars. Those were hydraulic and would shift between OD and direct without lifting off just like an automatic trans.

On draining and refilling, you can drain through the main box but you should refill through the filler on the OD section since it's on a higher level than the main box filler. Also, don't use any oil in it marked "hypoid". That is differential oil even though many modern manual transmissions use it. Hypoid oil will attack the brass synchronizers in older transmissions.

Here's the official B-W OD manual. It explains a lot of the operation, troubleshooting and repair.

http://www.oldcarmanualproject.com/m...rive/index.htm

[rotorwrench]

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The solenoid can be removed by taking the two mount bolts out and rotating the housing about half a turn to disengage the pawl in the transmission. It may have dirty points or something inside the solenoid on the ground switch points for the ignition (there are two sets of points in there). You can test it but you need a diagram to know which terminal to attach to. The two terminals should be marked or at least have color coded wires on the late replacement types.

The the overdrives used to have a rail switch on the back of the housing where the plug you show in the photo is. The rail switch was discontinued in later 51 or early 52 so they may have needed to machine the bore there for the shift rail and just plugged the back of it with a rubber stopper or equivalent. I don't have a transmission that late so I don't know for sure. It could be plugged with a good quality sealant as long as the area to be sealed is good and clean. The rail switch was there to shut the electrics off when the cable was pulled out. I'm not sure why they discontinued its use but they did. All my earlier Mercury transmissions have the switch there but they have a boss and two screw holes for it and yours doesn't.

Gear oil should meet the GL4 rating and no more. They originally used GL3 low EP lube but that was replaced by GL4. GL5 is high EP and should not be used in any of the early Ford type transmissions and especially the Overdrives due to the freewheeling sprag in the back.

[40cpe]

It sounds as if your overdrive isn't engaging while driving. It is possible that the "click" you hear at 28 mph is the relay engaging. The relay can operate without the solenoid kicking in.

With the lock-out handle pushed in toward the dash, does the transmission "freewheel" (not provide engine braking) when you are off the accelerator?

[Frank Miller]

I've had Mobil 1 synthetic gear lube in my trans for over 40k. When will it destruct?
You should be able to feel the OD shift, more noticeably in second gear. If that is not happening there is your problem. If it is engaging make sure the switch is adjusted properly. I need to fully mash down my gas pedal. If you need to remove the solenoid you can take the cover off to inspect the points. One set switches between the pull in and hold coil. The other set completes a ground when solenoid is energized.

[Charlie ny]

Britch,
That rubber bung should be a small soft plug, the hole just happens to be close enough in size to tap out to 1/8 npt. The OD kick out shaft rides
in that hole, the shaft as you know is actuated when you shift the trans into reverse.
Charlie ny

[Ross F-1]

Originally Posted by 40cpe

....
With the lock-out handle pushed in toward the dash, does the transmission "freewheel" (not provide engine braking) when you are off the accelerator?

Excellent point! It isn't in the Overdrive position if it isn't freewheeling, despite whatever position the lever is in.

[40cpe]

Originally Posted by Ross F-1

It isn't in the Overdrive position if it isn't freewheeling, despite whatever position the lever is in.

Or maybe the overdrive section is frozen/locked up. Too many were ruined when the OD section got too low on gear oil.

[40cpe]

delete double post

[Britcheflee]

No it does not - going downhill on the freeway I am constantly on the brakes as it wants to run away on me - just like having the clutch in.

[flatheadmurre]

Originally Posted by Britcheflee

No it does not - going downhill on the freeway I am constantly on the brakes as it wants to run away on me - just like having the clutch in.

That means you´re in freewheeling mode.
Pull the handle out and see if it engine brakes.
If it does the lever mechanism works as it should.
If the internal wouldn´t shift reverse don´t work if i remember right.

[krackerjack1951]

ck your of cable at the trans..the cable has to be fastened there for the core to move the handle on side cover forward or rearward must, must must ck that...old school lesson...

[Mike51Merc]

Couple of things: The "engine killer" wire on the solenoid will only ground when the solenoid is fully engaged. There are a set of contact points inside the solenoid that will only touch when the solenoid is fully extended.

The engine killer circuit is run through the throttle switch before it goes to the coil (also remember the coil wire goes to the distributor side of the coil, not the power side).

The throttle switch is a DPST (double pole single throw) and does two things , it interrupts power to the solenoid and kills the engine. The moment that the solenoid retracts, the engine comes back to life.

So, to kill the engine, you have to first actually be upshifted into OD (not just enabled, but actually upshifted) and you have to press the throttle to the floor.

The sensation of OD upshift/downshift feels exactly like an automatic transmission shifting up or down.

As for your bunghole, can't say I know anything about that....

[Britcheflee]

Thank you all for your great comments and advice. As I am certain all the wiring is correct I have a feeling that Mike51 may have a good point - the solenoid is clicking/clacking however, either it is not fully engaging the system or there is something wrong with the points inside or possibly both - there is a pretty good ding on the side of the solenoid maybe from a rock or something which might be affecting it. I will try the lever in/out test (can you safely pull this in and out whilst the car is moving?) - also I had my buddy pull the OD cable in and out when I was under the car and I clearly see the lever moving fully back and forth. What is odd is that the engine did cut out when I had the old wiring in place but I have a feeling that might have been because the cloth wiring had chafed and there was bare spots on it allowing it to ground another way? Either that, or for the first time the solenoid was activated and it moved some crud in there. I am going to remove it and give it a clean and inspection. Thank you all for your help.

[Britcheflee]

Originally Posted by flatheadmurre

That means you´re in freewheeling mode.
Pull the handle out and see if it engine brakes.
If it does the lever mechanism works as it should.
If the internal wouldn´t shift reverse don´t work if i remember right.

I can do this when the car is moving?

[donald1950]

only under slight acceleration.. best done with car stopped.....

[40cpe]

You can move the lock-out cable while moving PROVIDED the overdrive is not engaged, AND the accelerator is applied enough that the engine is pulling the car.