Overdrive transmission woes

matchbox_greg

Hello friends,
My 1948 Commodore came to me equipped with a 308 and overdrive transmission from a 1951 Hornet.  The transmission has never been a problem.  The last two times out I've had episodes where it either won't drop into overdrive when I let off on the accelerator, or it will drop out of gear while cruising along.  
I know enough to be dangerous with such things.  Could this be as simple as the fluid level being too low?  And if so, there is not a dip stick for the transmission fluid level, right?  I'm guessing there is a fill hole somewhere on the outside of the transmission. I would pull that plug and add fluid until it starts coming back out at me.  
Or is it more likely that there is a more significant problem that is going to require a more invasive diagnosis?
Thanks for any input you might be able to provide.
Thanks!

cchancel

With overdrive, it is often electrical.  I doubt fluid level is contributing to your problems.  The fluid level is controlled by filling even with the fill holes on the passenger side of the transmission and overdrive.  I would start by checking the O.D. kickdown switch opposite the accelerator pedal on the engine-side of the firewall. If it is jammed down or worn out, the overdrive won't engage or could drop out at times.  The O.D. solenoid could have issues, as could electrical connections (as a friend of mine experienced in a situation like yours).  Unfortunately, electrical problems are a lot like plumbing: you have to trace the lines until you find the problem.

The overdrive and transmission each have a fill plug on the same (passenger) side. The drain plug points down for each. 75-140W Royal Purple gear oil works great in both.

There is a lot of information here:  https://hudsonrestoration1948-54.com/Transmission.htm

Geoff

First thing to do is check the lock-out switch, and that the o/d lever is being moved fully rearward by the control cable.  If that is okay, then move to the  governor switch contacts.   the governor  energises the relay, which  in turn activates the solenoid, which activates the  overdrive mechanism.   It certainly won't be the transmission oil  causing the problem.

Jon B

Geoff, does Greg (?) need to be sure to use a GL-4 transmission oil so as not to corrode his "yellow metal" parts in the transmission?  Or are there any brass or bronze parts in the post-war transmissions / OD's?

Greg, if you look in the shop manual (which can be found in the online Hudson library, I believe), you'll probably find a troubleshooting section which may help pinpoint the problem.

As to the in-out control knob under the dash, just be sure that when it is fully pushed in, there is still about 1/8" of the rod (to which the knob is attached) showing, where it enters the hole in the bracket.   In other words, you want to be sure that the cable (controlled by the knob) has pushed the lever on the OD case, its entire travel.   If the knob hits the dashboard bracket when you push it in,  the bracket may prevent the cable from moving all the way.  And the cable won't have moved the lever (on the OD) its full travel. Thus the OD will be "halfway engaged".  So, you want to see a bit of that rod (to which the knob's attached) showing, when the knob is pushed in.

Likewise, you want to be sure (as Geoff says) that the lever on the OD is being pulled all the way to the end of its travel, when you have pulled the knob out.  Get under the car (with the knob pulled out) and observe where the cable connects to the OD lever.  You want to make sure that the cable sheathing has not moved on its bracket (to which it's clamped).  If it has moved, then when you pull the knob and the cable pulls the lever, the lever may actually bottom out on the sheathing before it moves its full travel.  In this case, the OD may not be completely locked out, and you will still be in free-wheeling.

(Have I confused you completely?)

matchbox_greg

Gentlemen, many thanks!  I think you've collectively given me some things to focus on initially.  I sincerely appreciate the help.

kamzack

Had a similar problem and was suggested I remove solenoid, remove top and if has gear oil in it, the gear oil may be disrupting connection between hold in contact  points. If so clean all oil residue and replace seal between solenoid and trans case. Small O ring. Solved the problem.

matchbox_greg

I spent time on the under the Commodore this morning.  The wire connecting to the solenoid was soaked in transmission fluid and the metal was exposed through the fabric casing.    
I cleaned that up and covered the end of the wire with a heat-shrink wrap.  


I played with the kick-down switch inside the car.  It seemed fully functional.  I sprayed the firewall side of the kickdown switch with some carburetor cleaner just to more fully assess that side.  I also used some electrical tape and shrink wrap on the two-wires connecting at the base of the coil.  I don't know which of these efforts had an impact but when I took it out on a test drive the overdrive behaved perfectly!  In the half hour I drove it, the overdrive never failed to engage and the kickdown performed flawlessly.  
That transmission and overdrive both seem to be dripping fluid.  I don't have fluid here at the house.  I'm going to have to check that level and get those leaks sorted.
I'm also thinking it may be time to think about a new wiring harness for this car!
Thanks to you all for your help!  It's working.... for now!

Park_W

Open up the governor and clean it up, and I think you'll be back in good shape.  The innards of the governor get crudded up, including the electrical contacts.   Those contacts have be closed for the system to engage.  Don't be afraid to remove the cover of the governor … the innards are very simple.