Friday, December 15, 2017 11:27:47 PM

overdrive intermittent

5 months ago
#2527 Quote
My 1950 Ford Custom club coupe 8BA has an intermittent overdrive problem that I cannot find a fix for. When driving the car after it has not been run for several hours the overdrive works like it should for about 3 or 4 miles, then quits engaging. It does this same thing every time I take it for a drive.

Have read all I can find about this problem and checked connections, etc. Contacts in the solenoid and relay have been cleaned. I have done the tests found on the internet and all checks okay, when grounding the THSW relay terminal I can hear the relay and solenoid working. Fuse is good and connections cleaned. The wire from the relay SOL terminal to O/D solenoid has been replaced with a 10 gauge wire. The 6 volt battery is almost new and holds a good charge.

Any possibility this is a bad kickdown switch?

Any help will be appreciated.
5 months ago
#2528 Quote
Hey Clint,

Welcome to the Shoebox Forum!  Well, my exposure to the on-again, off-again, early-1950s Fomoco overdrive is a long-time, haphazard one.  But I'll try to help anyhow.

I used to get an overdrive symptomology (?) like yours when a lack of sufficient lubricant in the overdrive portion of the transmission would cause to unit to seize up when hot due to excessive friction.  I learned after some incidents with this problem was that my overdrive compartment and main transmission gear compartment were connected by a small internal hole which allowed transmission lubricant to flow back and forth through the whole overdrive case as needed.

Well, you can guess what happened after many years of operation when the rear transmission to driveshaft seal failed, causing lubricant to get past the seal.  So for me, renewing that seal was part of the solution.  The other part proved to be making sure that I separately checked and filled the overdrive portion of the transmission case slowly until topped off, even though I already had filled the rest of the transmission through the larger main filler plug.

Voila!  That usually stopped the symptom of excess friction and heat in the overdrive unit and solved the problem for me.  I hope this is all that's wrong with your rig, and that you'll soon be breezing down the road with rpms just loafing along at highway speeds.  Be sure to post your results here on the Forum, whatever they are, so that we can learn right along with you as you go.  Thanks and good luck!

5 months ago
#2529 Quote
Thanks to mr50s for the possible fix. I removed transmission and overdrive fill plugs this afternoon and topped them off with gear lube but this did not take care of the problem. The o/d worked as it should for about five miles, then would not engage.

Any help will be appreciated.

Thanks,  Clint
5 months ago
#2530 Quote
Hey Clint,

Good for you for trying my "fix".  Before we go on to try something else, can you tell me approximately how much trans. fluid each compartment required in order to become completely filled?  Also, how many miles did you drive your car before the trouble came back?  Also also, did my "fix" work right up until the time of the first failure to engage?  

Thanks in advance for your reply and again, good luck!

4 months ago
#2605 Quote
Overdrive fixed!!!

After trying every known fix other than taking the o/d unit apart I bought a new relay as a last resort .... that did it. The relay tested good even immediately after the overdrive quit working. Perhaps the relay coil was opening up after a few minutes operation? The old relay was pretty rusty before I cleaned it up so maybe there was too much resistance in the rivet connections? Anyway, the overdrive is working! Thanks for the response to my post.