I agree with Dobie, GL-5 hypoid gear oil is not recommended for the trans or overdrive. I use Redline MT-85 which is a GL-4 intended for manual transmissions with brass synchros. Viscosity is comparable to the factory recommendation as well.

I can’t say whether the use of hypoid gear oil could be affecting overdrive engagement.



1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Hmmm, probably the wrong stuff. STP says it's for axles and non-synchro transmissions. It likely contains hypoid additives for axles. Hypoid additives aren't good for our transmissions because they attack the brass synchronizers. These transmissions want a straight mineral oil without hypoid additives. Tractor Supply has it under the brand name Traveller Ford Tractor Transmission Oil. NAPA  Auto Parts also has it but may need to order it from their warehouse.

I am using STP 80-90 weight gear oil.

Alan, I asked about the idle speed because for a while my car was hanging up slightly when I would back off the gas due to a minor linkage issue. When it did this, the engine would only slow to something like 800-1000 rpm, and I would not get an overdrive shift until I hooked my toe under the pedal and pulled it back to drop the rpms down to 650 or less. There has to be a certain amount of “drag” from the engine on the input side of the overdrive to get the blocker ring to move out of the pawl’s way. In your case, if the shift only happens when you mash the kickdown switch followed by pedal release, perhaps the momentary loss of ignition paired with throttle release is causing the engine to drop rpms very quickly and thus generate the needed “drag” to shift the blocker ring.

I need to look at the manual again but I think there was a comment about the amount of friction between the blocker ring and the sun gear plate.

What are you using for gearbox oil?

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Peeeot....I don't have a tachometer but I would estimate the idle speed at maybe 500-600 RPM.  I was having trouble with the accelerator linkage sticking and not quickly returning to slow idle.  I solved that problem last week when I fabricated a new longer adjustable rod which attaches to the carb.  The rod that was on the car was a little too short so the linkage would hang up without returning to slow idle.  Yes, when I engage the kickdown switch the engine momentarily cuts out. 

Alan, I’m glad to hear you have been able to get overdrive! Questions: how high is your idle speed set? Does your throttle linkage readily snap back to idle setting every time? And, when you engage your kickdown switch, does it interrupt the ignition briefly like it’s supposed to?

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Try swapping solenoids with the convertible.  Oil, low current, etc. can effect operation of the sometimes finicky devices.  If the police car issue continues, you can at least rule that out.
‘BTW: If the seal leaks at all, installing solenoid upside-down can inhibit draining.

6 VOLTS/POS. GRD. NW INDIANA

Don't ask me how or why but the OD is now working (sort of).   First, there is now freewheeling in first gear under 27 MPH.  Also, I can do easy clutchless shifting to second and third gears while driving.  Here is how I got it to engage the OD:  I took the car up to 55-60 MPH, let off but no shift into OD.  However, when I hit the kickdown switch and then let off the gas it does shift into OD!   I tried this several times and it worked each time.  Although the trans is not exactly working as it should, I will leave well enough alone as I can at least get the OD to engage.  My only problem now with the trans is an oil leak.  It is not leaking at the solenoid, the speedometer cable or the governor.  It is hard to see where the oil is coming from but the leak looks to be in the area where the OD section bolts to the rest of the transmission.  I tightened the four bolts which attach the OD to the transmission but the leak persists.  Does anyone have a solution short of pulling the transmission and resealing it?  Thanks

My experience with clutchless shifting matches Dobie’s. 1-2 is easier than 2-3. I usually just use the clutch pedal.

Sounds like you are familiar with normal overdrive behavior from your Mercury, so that definitely helps!

Let us know what you find regarding freewheeling. I think that is critical information in the diagnostic process.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Clutchless shifting is possible when the OD is enabled but not engaged. In other words the OD cable is pushed IN but your speed is below the governor cut-in speed. When you let off the gas below the cut-in speed the freewheeling clutch acts as the clutch, allowing you to shift gears. When I do it the stick feels a little stiff compared to a normal shift.