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Blue label OD does not disengage

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artmck

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Not sure if I have asked this here yet, but my OD (in a '74) does not usually disengage properly. I bought it with no history, cleaned it up, checked the screen, etc and put it in ~ 2yrs ago. I now have it out and need an idea of where to go with it.

My first impulse is to remove it from the trans and just go through it, but are there things I should look at before I disturb anything? I'm quite sure it is not an electrical issue, it can usually be taken out of OD by a quick on/off the throttle after the switch is turned off. It always engages fine. The first few times I used it it did not do this, it crept in after several months of use.

Thanks for any input...
 
My only thoughts are to see what oil you were running in it. Quantum Mechanics had an article about the incorrect oil having too much pressure and locking it into position. Look them up on line and see if the article is still up on the website. Other than that I will not be able to assist. Bob
 
Mine stuck a little when I first got it and the PO used 30 weight oil. It was no big deal and hardly noticable. Based on the input from BCF, I switched to 20-50 when I went through the first change of fluids. A few days after that, I noticed the OD was shifting in and out (esp out) much better. It may have been a coincidence, but I don't think so...I'd say it was the Castrol ;-)

Bruce
 
Austin Healey's use a throttle switch to prevent disengagement unless the throttle is partly open. Your symptoms sound normal for that if your MG has a throttle switch, (I don't know if they do).

Otherwise,
The OD uses oil pressure to overcome spring pressure to engage OD. Relieving the oil pressure allows the springs to disengage the OD. An electric solenoid opens a ball valve to allow the oil pressure to engage. So with this knowledge, problems with disengaging could come from a solenoid that doesn't retract, a blockage in the oil passage that relieves the oil pressure, or problems with the springs that disengage the OD.
 
I checked the ball valve, it seemed to be correctly installed. I do notice some oil around the solenoid, so I was thinking maybe it was preventing the pin from moving down. Is that area supposed to be dry?
 
That area should have no oil in it. Though I doubt that oil would be preventing the pin from dropping. You didn't answer my question about whether you have a throttle switch that limits disengagement until you open the throttle partially. Also, what is a "blue Label" OD?
 
I think your '74 has an LH type overdrive like my MGC, right?

I had a problem with mine not dropping out of overdrive after every oil change. Yes, I took out the filter screen and the magnet and cleaned them at the same time. Had to go back under the car a couple of days later and pull the solenoid and ball valve out, clean it out with a "Q-tip" and replace the solenoid every time. This took care of the problem until the next oil change.

Eventually got tired of that old routine and switched to Mobil 1 synthetic oil and it never happened again. Changed to Mobil 1 in my 3000 Mk III overdrive gearbox, too.

C Ya,
Mark
 
I think it is LH, it is from an '80. My car did not have one originally. There is no throttle switch on these cars. I think I'll double check the relief valve and any sealing that should be present above the solenoid area. Mostly spending time tearing down the engine for a rebuild, I'll gather info on this and attack while the machine work is being done. Need to decide about the supercharger...

Thanks-
 
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