Hi, I've got a '66 1/2 ton with a 352 3 speed w/overdrive. When I push the overdrive handle in to engage, it will free wheel but not engage in the overdrive gear. I was told that it might be the solenoid but it responds fine when bench tested. It seems to me that it might just be a cable adjustment. Does anyone know the proceedure and am I on the right track. With the high price of fuel, it seems silly not to have the o/d working. Steve

 

First, I suggest you search here at FTE with T 85N and my name. I did a number of writeups on the Warner OD, and think it may help.

Second, let me explain how it works.
The OD cable when pushed in allows the OD to engage (after free-wheeling, also called direct drive), or locks it out when pulled out.

The governor is on the passenger side of the transmission. At about 30 MPH, it closes the relay circuit.

When the governor-relay circuit is closed, it closes the relay-solenoid circuit, sending power to the solenoid and punching the solenoid and the pawl up into the transmission to engage the OD unit.

There are 2 circuits inside the solenoid (hence the 2 wires). The first one is a heavy duty "push" circuit, which rams the pawl home. The second is a lighter duty "hold" circuit.

When power is sent to the push circuit in the solenoid, the solenoid shaft moves contacts inside it to transfer power from the push circuit to the hold circuit.

All of these circuits pass through the kickdown switch under the accelerator. When depressed far enough, as when lugging the engine under load, the kickdown switch terminates power to the solenoid. Simultaneously, it interrupts power to the coil, thereby killing the engine.
This process is necessary to take the torque load off the drivetrain, and allow the solenoid and pawl to slip out of OD and back into direct drive mode.
Dropping out of OD this way returns the 21% or so gear ratio to the drivetrain, and lets you power on up.

When the engine dies, the driver automatically lets up and off teh kickdown switch, which returns power to the engine. As long as the acceleration factor on the driveline is enough to keep the solenoid from pushing the pawl back up, the transmission will stay in direct drive. When the gas is let up enough to reduce torque on the driveline, the solenoid and pawl will push back up into position, and return the transmission to OD.

 

Testing:
Test for proper cable operation.
1. Jack the rear of the truck off the ground; use safe jacking and blocking procedures, etc etc.
2. The engine should be off, and the transmission should be in 2nd or 3rd gear.
3. Push the cable in to the OD position.
4. Check that the OD lever has moved to the REAR of the transmission.
5. Attempt to rotate the driveshaft. It should rotate freely in one direction, but not the other.
6. Pull the OD cable out to the LOCKED or direct drive position.
7. Ensure the lever has moved to the FRONT of the transmission.
8. Attempt to rotate the driveshaft; it should not rotate at all in either direction.

If either of these tests fail, attempt to correct the situation by adjusting the cable. If the driveshaft still does not perform as described above, the OD section of the transmission is most likely in need of repair.

If the driveshaft performs correctly, the circuits need to be checked next. Test the overall circuit this way.
1. With the ignition in the RUN position, remove the governor wire from the harness under the truck. (The governor is on the passenger side of the transmission.)
2. Ground the harness end of the wire. You should hear the solenoid click as it attempts to push the pawl up.
3. If the solenoid clicks, then the circuit is OK.

If the solenoid clicks, but the truck fails to engage the OD while underway, then you most likely have a faulty governor, or perhaps a weak solenoid.

If this fails, you need to troubleshoot the relay next.

1. Inspect the fuse on the relay, on the firewall next to the master cylinder. Check it for continuity even if it looks OK.

If the fuse is OK, check for power to the relay. There are 4 leads to the relay, top, bottom and 2 sides.
Top: Blue #14, supplies power from the energized relay to the Blue wire on the solenoid.
Upper side: Fused.
Lower side: Black #14, receives power from the backside of the ignition switch, thus supplying power through the fuse to the OD system.
Bottom: #18, Red with White stripe, comes from the kickdown switch.

With the ignition on in the RUN position (NOT the ACC position):
2. Check for 12V at the lower side lead of the relay (bottom of the fuse). There should be 12V here.
3. Check for 12V at the upper side tab. There should be 12V here, indicating the fuse and the connections are OK.
4. If there are 12V at the top and bottom side tabs, then power is being supplied to the relay. If not, then you need to trouble shoot the circuit behind the dash.
5. Check for GROUND continuity at the bottom tab. To do this, have someone ground the harness side of the governor circuit under the truck while you check for a ground. This test will ensure the circuit between the relay and the governor is working. It runs through the kickdown switch under the accelerator pedal, by the way. 6. With the power still in the RUN position, ground the bottom tab.
7. With the bottom lead grounded, the relay should click, and the top lead should now be energized with 12V.
8. If the top lead is energized with 12V, the solenoid on the transmission should attempt to actuate.
Listen for the OD solenid to actuate when you ground the bottom lead. If the circuit is in good working order, the solenoid will click as it attempts to engage the OD pawl.
9. If the top lead does not show 12V when the bottom lead is grounded, the relay is probably bad.

If Step 1 fails to energize the solenoid, but Step 6 is successful, there is most likely a problem with either the governor or the kickdown switch.

I have done this from memory and experience, so it may not follow the factory recommendations precisely. I hope however, that it gives you a good basis to begin troubleshooting.

 

What he said and the overdrive will not engage untill you lift off the throttle

 

...at speeds above 25/30 MPH

 

I will go through your comprehensive 9 step checklist. I had already checked the fuse on the firewall and it is OK. I am aware that you have to lift off of the accelerator to get the OD to engage. Thank you for all of your effort. Steve

 

I've been working on retrofitting the electricals on my o/d. Banjopicker, can you confirm for me that the governor is actually proving the ground for the relay switch? That is, when it kicks in at 30mph-ish it establishes a ground which closes the relay switch and sends power to the solenoid?

Question #2: even without a kickdown switch (I'm using a dash-mounted manual override switch), I still need to hook up both wires on the solenoid right?

The bird's eye view is this:
- switch at dash provides 12v to relay switch from ignition
- relay's higher amperage circuit receives 12v from starter relay
- governor grounds relay switch
- when switch is ON and governor makes ground (>30mph), o/d solenoid receives 12v on both blue and yellow wires (on mine, those are the colors used)

Thanks for your help - it's been invaluable already.

Aaron