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AH 3000 Overdrive - sticking engaged

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jtownhealey61

jtownhealey61

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Hello All,

I have a problem with by AH 3000 Overdrive.
In hot weather (in NC)with the engine hot, the overdrive will stick engaged and will not disengage until the engine(OD)cools back to ambient temps. I run SAE 30 weight oil and keep it changed. The OD functions perfectly during the cooler months.

Has anyone had this experience?
Any assistance is appreciated.

Regards,

Larry
 
Larry,
My guess would be that in the warmer temperatures, something is expanding just enough to cause it to stick. The only two things that come to mind are the operating valve (easy to get to and clean up) or the accumulator piston (possible to do in place, but a real bear if you are old and creaky). Oil pressure holds it engaged (owww, it's a long time since I thought about OD machinations, hurts the brain), and it sounds as if your solenoid is working, so I would ask if when it is stuck, and you come to a stop, with the OD switch still on, put the shift lever in neutral and wiggle it left to right. You should hear the solenoid click on and off. If you do, but you are still stuck in OD then something internal is sticking. The other possibility is that it is on the feather edge of being improperly adjusted and when things expand in the heat, it goes out of adjustment. Ya got a manual? Rigging is not hard, but you need a few things and a good explanation.
 
I suspect your od linkage is adjusted improperly. When the solenoid is in the off position, the release lever is down and should cause the hydraulic valve ball to seat firmly and cut off hydraulic pressure to the OD. Yours is probably adjusted so the ball just barely seats at normal temps. When the system gets hotter, the oil is thinner and the release rod just a tad longer -- and the ball does not seat well enough to stop the oil from flowing.

Well, it's just a theory, but it could explain your symptoms. To check it out, just set the OD lever a tad higher on the release shaft and I think your problem will go away. There is a detailed spec on this adjustment you can find in a shop manual.

There is also a relief port (pinhole) on the valve shaft that must be open or the OD disengage slowly if at all. I doubt if this is the problem because I don't see how temperature would affect it, but it should be checked as well. If you withdraw the vertical valve shaft below the ball, you can see the port and make sure it is clear.

Good luck!
 
Jon,

I am thinking along the same lines as you. I will check the adjustment.

Thanks for the guidance. The people who participate in the forum always seem to have some good advice.

Regards,

Larry
 
Thanks for your suggestion on the valve.
I am going to pull it and confirm the port is clear.

I will get back to you guys and let you know how it works out.

Regards,

Larry
 
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