Hi, I have problems with my 49 Mercury overdrive. When I start the car and go driving the overdrive works perfectly. I go in the 3rd gear lift the accelerator and the car changes in the overdrive. But when i drove for a while an the car gets on temperature the car didn't shift in the overdrive anymore. It is only free wheeling! I think its maybe a temperature problem. Any ideas??? Thanks Frank
Chances are the solenoid is going bad.....what you described is fairly common on old solenoids. A new one may be necessary. An NOS solenoid would be best (if you could find one) but reproduction units are available. Either way, they’re not cheap. Before you spend your money on one, try to make sure the wiring is up to snuff. Check every wire in the overdrive harness for tight connections. Clean and tighten every ground connection for the car including your firewall ground strap. I’ve also recommended that guys add a new ground wire down at the transmission.....connected to the body and a transmission bolt (preferably one of the solenoid mounting bolts). The factory ground for the overdrive system was through the tail housing casting to the gearbox, to the bell housing, to the engine block, etc. Unless every surface was clean and tight, your ground for the overdrive is degraded some, causing poor performance of the overdrive electrical system.
I have a '49 Merc with overdrive and it doesn't release all the time. Everyÿthing has been cleaned, solenoid checked. I onlyÿ show 0.6v at the relayÿ solenoid terminal with the ignition on.? Seems like if no traffic is behind me and I can slow down graduallÿ, all is good. Else the overdrive locks up and won't disengage. Suggestions?? Thanks!
I doubt .6 volts can activate that old solenoid, but that's just my guess. Let's see if @Crazy Steve can help with post above. Or maybe @Mac VP can help.
Don't be too quick to condemn the solenoid. First, is the gear oil level in the OD unit full? These don't fill through the transmission fill (even though they share a common drain), it has its own fill plug and MUST be filled there. The other thing I'd check is the operation of the governor. It contains a set of centrifugally controlled contacts that do the actual switching of engaging/disengaging the solenoid according to speed and if dirty/rusty/gummed-up it may not be working right. Removing the solenoid and disassembling it to make sure the contacts are clean and all moving parts move freely may be the fix. If you're checking the OD relay with the key on and the car is NOT moving, there shouldn't be ANY voltage at the solenoid terminal. So the relay is suspect, I'd try removing the cover and look for burned/sticky contacts. You may need a new relay. You can substitute a common Bosch relay, you'll just have to install an inline fuse in the power lead. But it again may be an issue with the governor. Check/clean as above.
I don't think that there should be any current to the relay solenoid terminal. The Governor is the gateway switch which sends the 12 volt (or 6V if a 6V car) at ~28 mph.
If you’re filing the transmission with gear oil for the first time, you can speed up the process by pre filling the overdrive section through its filler plug. However, since the ring gear sits practically at the filler opening, it’s difficult to put oil through the opening unless you turn the transmission on its side. So prefilling it with the trans in the car can end up with you oiling the garage floor as much as the transmission. We suggest prefilling the OD section with the transmission on the bench, and then finishing up the filling through the main filler plug in the side of the 3 speed gear box. Be sure to allow time for the oil level to equalize….. top off as needed. From this point on, all topping off and checking oil level should be done through the 3 speed main case filler plug. There are several openings/gaps between the 3 speed section and the overdrive section for the oil to pass. So the final gear oil level will be the same for both compartments. This is why any future oil level checking and topping off should be done with the 3 speed side plug. This is how Ford recommended dealing with the matter. It’s not that you can’t or shouldn’t utilize the overdrive fill plug….it’s just a difficult and messy job to do so with the transmission in the car. Lastly, it’s important to keep an eye on the gear oil level for this type transmission, especially if it’s not freshly rebuilt with new seals and gaskets. When the oil level drops a couple inches, there’s still plenty of it thrashing around in the 3 speed section. However, the sump part of the overdrive housing is not as deep and you run the risk of letting the planetary gear run dry, resulting in burning it up. This means nasty noises, no overdrive, and an expensive repair. I’ve seen plenty of examples of this failure in our shop over the years.
The above is faulty advice for this reason. Unless you have a spare driveshaft slip yoke in the output shaft, gear oil will pour out. Mounting a transmission is hard enough without the challenge of a gear oil spill. Instead, mount the transmission, install the driveshaft, fill the overdrive section with gear oil till it begins to weep then affix pipe plug, fill main transmission till it begins to weep then affix it's pipe plug.
It goes without saying that (whether it’s a regular 3 speed or overdrive type) gear oil can and will run out of the tail housing if one tilts the trans without closing off the opening where the output shaft protrudes. A special plastic plug or an old slip yoke is commonly used. A plastic bag and a zip tie will work in a pinch.
Is the voltage 0.60 volts? I have a friend with a similar Borg Warner O/D trans. Wouldn't shift into O/D. After some significant troubleshooting it was determined that the solenoid mounting surfaces were greasy and corroded, preventing an inadequate ground to pass enough voltage to the solenoid. Cleaned and sanded everything. Works great!
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