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Overdrive Issues

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JoshP

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'77 MGB w/ LH Overdrive...a little while back, I did a complete lube on my B (motor, trans and rear axle fluids changed out). While servicing the trans, I removed what I "thought" to be the drain plug in the OD. Only...surprise...there is no drain plug. What I removed was the plug that holds the low pressure relief valve. I found it later in my drain pan when I was emptying it.

I put it back in with the narrow side up and the little round filter screen at the bottom (it wouldn't go in the other way). Today, I have my B out for a drive and I switch to OD and...nothing. Nothing at all happens. I believe it to be the valve; I probably installed it incorrectly.

Long story short, can anyone offer any suggestions or advice? I should add that the gearbox oil level is correct, Castrol 20w50, and I did clean the OD filter/magnet set.
 
Josh,
If the complete low pressure valve assembly fell out (about twelve parts) then you will need the factory manual to reassemble correctly. Usually the main part of the valve stays in place and the only part you can remove easily is the filter.
Alan
 
I found a pic of the part which fell into my drain pan...it's the top part with the silver filter screen. I reinserted it with the narrowest end at the top; it wouldn't fit the other way with the screen up. The other piece is either still in the OD or gone forever.

The pic is attached to this post...
 

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I did a similar dumb trick years ago, never did get it to work again! In my case it was a metal ball about twice the size of a BB shot. All those "plugs" on the bottom of the transmission look alike, especially to a novice. Bob
 
Bob, that sounds like the OD solenoid that you removed. Was it behind a blue or black labeled cover?

FWIW, a trick I read about to reseat that ball was to put a dab of grease on a punch and press the ball into the grease. Take the punch/ball and seat it into the top of the solenoid housing with a couple taps of a mallet. Reassemble everything else in order and all would be well again.

When I was servicing my trans, the instructions in Haynes called for the OD drain plug to be removed along with the tranny drain plug. What I didn't realize (and this should probably find it's way into the Haynes book; scribble this into your page margin!) is that the drain plug is only on the Type D, not the Type LH overdrives.

Dumb oversight on my part ultimately; I definitely should've checked the diagram more closely. I'm just lucky that I saw the part in my drain pan and didn't pour it into the disposal drum. That's a big dollar part; even bigger dollars if I had managed to screw up my overdrive. Live and learn :p.

I'll get it fixed, one way or the other.
 
Yeow , that is a nasty valve. Was there any trash in the screen? Clean what you have there before you put it back. Anyway , at the top of the valve (bottom of the image near the arrow) should be a spring loaded check ball. See if it is there and will move with slight pressure. I'll see if I can send you an image of the factory parts book diagram.
 
Thanks, AlanT...that wasn't my own valve in the pic. It was just a pic of one I found to use for an example. My valve was pretty clean when I found it; the only piece I found was the top one in the pic, the one with the screen. The bottom piece with all the vent holes was nowhere to be found.

I've got a copy of the Bentley book coming; I chose the 63-74 version because my B is more or less in that configuration (twin HS4s, 25d dizzy). I have the Haynes for things specific to the '75+ models.

I'll dig into that assembly some tomorrow and see what I can find out.
 
Josh, I have used about every spare piece of LH overdrive stuff over the years. I doubt I have what you need. AT
 
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