Customs Merc rear end

The 4:11 gears with with normal size tires and the overdrive functioning properly, should be great! That is what I have behind a 200 cubic inch six! And love it!
If you think you are winding too tight at 55 with it in overdrive……some thing wrong!






Bones

 

Learn how to work that overdrive to your advantage. You have, effectively, 6 speeds forward to play with. Always use the overdrive on the highway. That's what it's there for. About 2800 RPM at 65 - 70 MPH. Using higher gears will kill your performance and gas mileage. I used to use the overdrive to split the gears when street racing. Wind it tight in first gear and hit the overdrive. You'll be surprised how quick the little flatty can get up to speed. OD shift down in second, wind 'er up, shift the OD up and you can get up to 70 MPH pretty quick once you learn to use it. Same with 3rd gear. Shift the OD down on steep inclines or whenever it starts to lug down. If I remember right I used to amaze people when I'd wind the thing up in reverse and kick in the OD. "How did you do that???"

 

Lol damn how did you do that????

 

Trying again-
The OD is comprised of 2 systems to make it work, mechanical and electrical.
Mechanical- the pull handle (in for OD use, out to lock the OD out), and the OD unit itself. The planetary gear in the unit could be stuck, or the pull handle cable bad. Either one is not likely if the unit is not noisy, and the issue is most likely electrical.
Electrical- consists of 2 major circuits- a power circuit of supply power through a fuse and relay to the solenoid, and a control circuit. The control circuit has a governor switch and kickdown switch which controls the grounding contacts of the solenoid and ignition distributor points. The governor switch disables the OD below 21 MPH, and allows it over 27 MPH. The kickdown switch disables the OD under full throttle, and momentarily shorts out the ignition to allow the planetary gear to release into direct drive.
A shop manual can be helpful.
Another option is regular 3 speed with rear axle gearing change.

 

Pretty much everything you need to know about the BW overdrive. Don’t be put off by Willys, it’s Ford too.

http://www.oldwillysforum.com/forum/TechData/BWOverdriveManual.pdf

For parts.
http://www.vanpeltsales.com/

 

It could easily be something else.... Here's the wiring diagram.




First thing to check is the overdrive relay; this should be mounted on the firewall. Make sure it has power to it when the key is 'on', and also make sure the fuse is present and good. Grounding the terminal for the wire from the kickdown switch will check operation of the relay. If the relay checks good, start tracing wires to the kickdown switch and governor to make sure they haven't broken. Make sure the switch has good internal connection. The governor may need some service as they're known for burned contacts over time, and it should be noted that this is what actually engages/disengages the OD under normal conditions (OD cable pushed 'in'). These can usually be disassembled and the contacts filed to restore operation. The governor will enable OD once vehicle speed reaches about 28 MPH, and will disengage OD when speed drops to about 21 MPH.

The kickdown circuit for passing or hill-climbing works like this... When in OD and you mash the gas the A/B contacts in the kickdown switch open, interrupting power to the OD solenoid. The C/D contacts in the switch close, grounding the ignition via the solenoid and stopping spark for about 1/2 revolution. This unloads the transmission, allowing the solenoid to shift out of OD. As soon as the solenoid shifts, the grounding contact inside the solenoid opens, restoring power to the ignition. There will be a noticeable hesitation while all this occurs. If you want to disable OD, pull out the cable before lifting off the gas. Otherwise, when you lift OD will re-engage.

When the OD cable is pulled 'out', the OD is mechanically locked out and none of this functions. DO NOT pull the cable out when the car is moving except as noted above. Failure to heed this can damage the solenoid/OD shift pawl.

Most of this wiring is under the car and takes a beating over the years, add in advanced age and probably brittle insulation on the wires and broken wires/poor connections aren't uncommon.

I'll note this is a '56 diagram so the wire colors/sizes may not match but operation will be the same.

 

Wow, great literature. Where do I send my 50 cents to get a copy?

 

Sorry, it’s going to cost more than that to run it thru your printer. But yeah, covers it pretty well doesn’t it. BW was kind of at the top of the pile for engineering in those days.