overdrive issues

dave11 · May 2015

The overdrive in my 52 Hornet is not engaging. Pushing the dash lever in and pass 20 mph it is still is 1 - 1 ratio. Although when I back off on the accelerator it free wheels.

I suspect it may have something to do with the generator, as everything (overdrive) was working fine untill I changed the brushes on the generator as it quit charging. I learned that when the generator quits charging the OD unit will not engage. After new brushes the generator light does go out once the engine starts and it is charging 8.5 volts ??

Dave

Jon B · May 2015

I'm shooting in the dark here, but I think you have to go more like 35 MPH to engage OD. Were you up to that speed?

If so, then I would guess that the governor has something to do with it. In your OD, I believe the governor is electric. You might simply examine the OD from under the car, and make sure that all the wires to the governor are still attached.

I'm no expert on the "full electric" OD's, 'cause mine is a prehistoric OD that is mostly mechanical! But someone will jump in here soon and give you some good info.

Glowplug · May 2015

Go to my website and select transmissions at the left side. The transmissions page lists all the operations and trouble shooting information needed to review and repair your problem.
http://hudsonrestoration1948-54.com/

Park_W · May 2015

The original system is indeed wired so if the gen is not charging, the OD will not operate (done so as to preserve battery power if the gen's not working). So that explains why the OD quit working, but leaves the puzzle of why it didn't start working again after the gen was fixed. (by the way, you should adjust the Volt reg so as to get about 7.2 volts. 8.5 is going to overcharge your battery).

You can change the OD wiring arrangement by finding the wire from the OD relay that goes down to the ARM terminal on the voltage reg. Disconnect this wire at the voltage reg. and connect it instead to the accessory terminal on the ignition switch.

J Spencer · May 2015

Park is right on with his explanation of the wiring, etc. The O/D should work OK if you didn't disconnect the wire at the ARM post on the voltage regulator. Doesn't seem possible that the wire from VR to relay would go bad but ? Could it possibly be the fuse at the relay blew? or a bad connection at the plug on the relay? Both of those things happened to me on my 51 Pacemaker. Jon's comment is also good as when speed reaches about 30 MPH contacts in the governor close and ground the relay to complete the circuit. It just seems odd that it would do it after you fixed the generator.

Yeas ago my friends O/D didn't engage, traced it to the governor, removed it, took the cap of cleaned the oil, etc. out of it, checked it on the bench by spinning with an electric drill and an ohm meter. Checked

OK , reinstalled it and it worked fine.

Park_W · May 2015

Jim, the problem of oil on the governor contact points is still a quite common cause of "suddenly it quit working."

48Sed · May 2015

Just finished cleaning the points in my governor and now all is working again.

The points looked clean when inspected but must have had some oxidation on them to cause the open condition.

dave11 · May 2015

Turns out I had a loose wire at the govenor . At the least I now have a better understanding of the OD system. Thanks for the technical insite gentlemen.

Dave Eddie