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Occational overdrive

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thomaslea1

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The OD still seems to work when it darned well wants to. It will drop the RPM's when the switch is thrown but only engage every now and then. If I let it keep decelerating and flip the switch OUT it locks up in non-OD mode with no problem. Sometimes after it does decide to engage it'll drop out by itself, and it may or may not decide to let me re-engage it. I've done all the o-rings, new non-return valve kit, both new balls, seated the solenoid ball, oil pump feels tight and is in correctly, new screen (the old one was clean). Blasted it clean with 2 or 3 cans of carb cleaner and air pressure. Tried 30W non- detergent oil, RedLine MT-90, a 32 viscosity mineral oil, and currently 20W-50 oil.

Before I tear it out and look at the clutch material on the sliding member, I have concerns about the relief valve. I've attached a photo of the valve in exploded, semi-assembled and assembled state along with it's measurements.(Actually the picture can be seen at https://www.mgexperience.net/phorum/read.php?1,1483917 )The sleeve (with the holes in it) covering the valve itself does not show up in anyone's catalog!! The assembled valve seems to be about 0.052" from reaching the end of that sleeve.

I hope: someone has the measurement of the assembled valve OR the correct length of the spring, OR both. Would really make my day. All I'm coming up with is that it's possible the top end of the valve assembly is not sealing against the housing on the inside top. I'd spend the $90 to buy the new valve assy, but I still wouldn't be SURE that it was the correct length.

I have photo's of everything, just cant figure out to get one in the text.

Thank you very much,

Tom

currently sucking down a Miller Lite and swearing at the OD unit.
 
Is the solenoid dirty? It could be sticking. OH, what overdrive are we talking about? What car and what year????
 
Blue Label put in a '68 and using the gearshift switch. Solenoid works normally and is spotless. Lock-out switch works fine too.
 
There is an inhibitor switch beside the shift tower. It may need to be adjusted. If you hold the shift lever to the right and it stays in overdrive, then the switch is the problem.

If not, then I would do the following. Remove the plunger and ball bearing. Put a dag of grease on the end of a punch, then stick the ball to it. Push the ball up into position in its seat, and smack the punch with a hammer. This will help seat the ball properly. Reinstall the plunger and see how it goes. This method fixed my overdrive a few years ago.
 
thomaslea1 said:
I have photo's of everything, just cant figure out to get one in the text.
Click to expand...

Here's a picture that Tom posted on the MGE....I believe it is what he would have posted here as well....
 

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Steve_S said:
There is an inhibitor switch beside the shift tower. It may need to be adjusted. If you hold the shift lever to the right and it stays in overdrive, then the switch is the problem.
Click to expand...

This was initailly my problem - chamged the switch and all was well. A few months later, another problem. Turns out the o rigns in the solenoid were bad. $12 and an hour later and I was done. John Twist and Esposito helped me through this diagnosis and I'm forever thankful.
 
I hate that MGB Experience changed to MG Experience because now everyone uses "MGE", which historically has been the abbreviation for MG Enthusiasts' BBS - another site altogether. Now whenever someone types MGE I have to try to figure out which site they're talking about! I still actually use MGBE, in protest. :smile:

The experience site is 90% MGB anyway...
 
SOLVED! Thanks for putting the picture in Rick. If you look at the bottom left plate of the photo, the valve assy does not come to the top of the perforated sleeve. Turns out that the spring had compressed over the years. Ken Quade sent me the spring measurement. His was 1.187" and mine was a good .120" shorter. His valve stood about .050" over the top of the sleeve. I couldn't find shim material to raise the valve, but the nut from a threaded lamp rod turned out to fit perfectly. Smoothed the corners off the nut and put it between the spring and valve and the valve now stands proud about .050" and the OD is no longer occasional!!!

Yes, I would buy a spring, but then seem to only be available as part of the whole valve assy for a measly $90 + shipping! Seems a bit steep for a 2" spring.

Now to build a test plug so I can get the pressures where they belong.

Thank you Ken Quade. BTW: Ken has a freshly rebuilt blue label OD he's looking to sell.
 
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