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TR2/3/3A Type A overdrive not engaging

DennisT

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Hi,
I just put my TR 3 back on the road after 2 years, got a growth paint job, and had the tranny/overdrive rebuilt. I noticed a couple of times the OD would clunk load when engaging and then it stoped engaging altogether. When I pull the OD switch the amp gauge does deflect so I m think maybe solenoid relates? Also I have quantum mechanics ebuild bothe the tranny and OD type A. It worked great all day yesterday however tonight it will not engage. Anybody have any ideas on this problem.
thanks,
Dennis
 

CJD

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With the ignition switch on, the engine still off, and the tranny in 4th gear (or any forward gear for later units), pull the OD switch and listen carefully under the car for the solenoid clack. There will be a smaller “click” from the relay under the dash...so make sure you listen under the car for a loud “clack” from the actual solenoid.

If you hear no clack, then trouble shoot the electric side, including the switch, relay, and tranny lockout switches. If you do hear a clack but still no engagement when you drive the car, then you will need to troubleshoot the mechanical side of the unit...most likely the solenoid arm adjustment.

If you tell us which way you need to go we can go into more depth for each...
 

mr.tr3

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HI
If every thing checks out with the wiring it could be the solenoid is bad it has 2 stages one that pulls the plunger up and one that holds it in place. When this happens it will engage but drop out.
 

Sarastro

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The initial pull-in uses something like 10 amps, so you will see a kick in the ammeter. The hold-in function uses only 1 amp, so you probably will not see that on the ammeter.

As others have stated, the first step is to determine whether the solenoid is engaging properly. You really should be able to hear it when it engages and when it disengages; it makes a pretty obvious clunk.

Since you are seeing something on the ammeter, it seems that the wiring is probably OK. So, if the solenoid isn't operating properly, the problem has to be a bad solenoid, or possibly something binding or some similar problem.
 

DavidApp

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Are you driving the TR3 and it is sometimes engaging and others not?

Got enough Oil in transmission?

David
 
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DennisT

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With the ignition switch on, the engine still off, and the tranny in 4th gear (or any forward gear for later units), pull the OD switch and listen carefully under the car for the solenoid clack. There will be a smaller “click” from the relay under the dash...so make sure you listen under the car for a loud “clack” from the actual solenoid.

If you hear no clack, then trouble shoot the electric side, including the switch, relay, and tranny lockout switches. If you do hear a clack but still no engagement when you drive the car, then you will need to troubleshoot the mechanical side of the unit...most likely the solenoid arm adjustment.

If you tell us which way you need to go we can go into more depth for each...

i put car in forth gear, ignition on, switched on OD switch, I hear the clink but no clunk, I will pull the cover and check lockout switches, OD wiring harness connectors, check arm adjustment, also measure ohms on the solenoid, both first and bottom position of plunger. Not sure but I think I smelled wiring insulation after I pulled OD switch out while running last night before I got home. Maybe solenoid arm did not travel all the way to bottom and cut in the hold coil so it remained on the higher 10 amp draw.
 

CJD

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That is a common failure mode. The solenoid will continue to heat up if the contact doesn’t break the high amperage coil in the solenoid, until the solenoid is damaged. I would start the test from the solenoid and work backwards.

There is a ground wire and and the hot (activation wire) going into the solenoid. The hot wire will go from solenoid to the cutout switches on top of the tranny cover. With the same conditions for testing, I.e. ignition on and in 4th gear and engine off, check the power at the hot wire to the solenoid. Remove the wire from the solenoid while checking, as a shorted solenoid may pull the voltage down to nothing. If you get a full 12+ volts at the solenoid hot wire, then you know the solenoid is the problem. If you are not getting power to the solenoid wire, then I would back up to the relay under the dash and see if power is actually coming out of the relay.

Another failure mode is the relay clicks, but the contacts get dirty and/or burned, so no power is passed through.

Since you did not get movement of the solenoid, you can wait to adjust the solenoid actuating arm. It is likely alright.

Oh, one last quick check is make sure the solenoid plunger is dropping. No clack can also be caused by the plunger sticking up, so it has no movement when engaged.

These steps should isolate the area you need to concentrate on...
 
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DennisT

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That is a common failure mode. The solenoid will continue to heat up if the contact doesn’t break the high amperage coil in the solenoid, until the solenoid is damaged. I would start the test from the solenoid and work backwards.

There is a ground wire and and the hot (activation wire) going into the solenoid. The hot wire will go from solenoid to the cutout switches on top of the tranny cover. With the same conditions for testing, I.e. ignition on and in 4th gear and engine off, check the power at the hot wire to the solenoid. Remove the wire from the solenoid while checking, as a shorted solenoid may pull the voltage down to nothing. If you get a full 12+ volts at the solenoid hot wire, then you know the solenoid is the problem. If you are not getting power to the solenoid wire, then I would back up to the relay under the dash and see if power is actually coming out of the relay.

Another failure mode is the relay clicks, but the contacts get dirty and/or burned, so no power is passed through.

Since you did not get movement of the solenoid, you can wait to adjust the solenoid actuating arm. It is likely alright.

Oh, one last quick check is make sure the solenoid plunger is dropping. No clack can also be caused by the plunger sticking up, so it has no movement when engaged.

These steps should isolate the area you need to concentrate on...

Thanks,
I will take the cover off tomorrow and investigate the hot wire to the solenoid first
 
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DennisT

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I checked power after the shutout switches and I am getting 12V I checked the ohms on the solenoid , it looks like 200ums but no change when I move the plunger. Looks like the adjustment arm is free and spring loaded I’m not sure but maybe a bad solenoid? It’s brand new but who knows, it was shifting in and of OD perfectly and then it’s started to slam into OD but disengaged very smooth
I ordered a new solenoid
D
 

titanic

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I found this article very helpful to me as I adjusted my solenoid arm.

Seems a very small adjustment can make a big difference. Adjustment starts at page 47.

David

https://www.thorden.dk/Teknik/A Type Overdrive.pdf
That article is from the Buckeye tech articles. Strange that the person didn't give credit to the author, Nelson Riedel. All of his writings concern the TR6, but the trans.&OD are pretty much the same as the TR3. https://www.buckeyetriumphs.org/gearbox
Berry
 

CJD

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It sounds like the plunger is stuck on the low current setting in the solenoid. You could check that by pulling the switch with power on the car and then push the plunger up by hand. If it does not move up on it's own but does hold after you push it up, then that's the problem.

While you wait for the new solenoid you can try popping off the rubber top on the solenoid. You may be able to clean the plunger and contact to get it working again. Then keep the new one as a back up.
 
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DennisT

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It sounds like the plunger is stuck on the low current setting in the solenoid. You could check that by pulling the switch with power on the car and then push the plunger up by hand. If it does not move up on it's own but does hold after you push it up, then that's the problem.

While you wait for the new solenoid you can try popping off the rubber top on the solenoid. You may be able to clean the plunger and contact to get it working again. Then keep the new one as a back up.

Ok I will try tomorrow,
thanks
dennis
 
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DennisT

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Hi,
just wanted to thank everyone, I pulled the old solenoid and it was burned out, replaced with new item and the overdrive works perfect, even though the solenoid was new when I put it in, it still failed. Hopefully it will work for a long time.
 
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