After restoration OD didn't work. AS per suggestions I removed console, tranny tunnel and pushed the lever on right side of tranny down and the OD engaged. I did not get the pinch bolt tight enough so the solonoid lever did not move the operating valve. I adjusted as per the book and the OD worked fine. I was able to engage and disengage. The lever on the right side of tranny was a little off so I adjusted it so it is aligned with the hole. Then I noticed that it engaged but didn't disengage the next time out. Today I started out with the OD switch off and when I shifted into third I felt the OD shift after about 4 seconds or so. Stopped the car, turned the switch on, the solonoid engaged, shut off switch, started out and the OD was still engaged when I shifted into third. Any suggestions would be apreciated. Have a good day!

John

John:

Put the adjustment back where you had it. No doubt the "correct" adjustment you just made leaves the OD valve slightly open when the solenoid is not activated.

My car is the same way, if I adjust it with that alignment hole as per the shop manual, it does not work properly.

You just need to set it so the valve is definitely open when the solenoid is engaged and definitely closed when it is not. I suspect you are very close to having it right.

To add to the drama there has to be enough stroke so the solenoid when activated opens those tiny internal electrical contacts to switch it from pull-in to the holding coil. Otherwise, you will draw too much current and possibly fry the OD wiring harness. I usually put an ohmmeter on the solenoid and work the OD linkage by hand to make sure the coil resistance increases when the linkage is moved manually to the activate position.

Bill.

John, I'm glad you tracked it down to the solenoid lever adjustment. Bill (above) has the right answer .. you adjusted it too far. Did you put the tunnel cover back on already?

I readjusted the control rod and it will engage and disengage but it is not consistant. Bill, you said you did not adjust as per manual. Does that mean your lever is past the hole or before the hole. I have not installed the tunnel so I am still trying to get it right. Do you have to depress the accelerator when you turn the dash switch on to get the OD to engage and likewise bump the throttle to disengage it? Thanks for the help and have a good day!

John

I know that if the throttle switch is adjusted correctly, you have to bump the throttle (depress the accelerator) to disengage OD. I've always had the accelerator down somewhat when engaging the OD -- never had to do anything else.
Is both engaging and disengaging inconsistent, or do you mean dependent on the throttle movement. If the latter, that is appropriate.

Sounds odd but if you recently changed the oil and overfilled it I had a similiar issue.


Michael.

John:

I don't remember if my lever is set short or past the hole (I think it is short), I just know it is not on the hole. Can't tell now without removing that bloddy tunnel!

The throttle must be cracked opened a bit to disengage the OD if the throttle switch is set properly. This switch has no effect on engaging the OD. If the throttle switch is broken or badly adjusted so it does not close when you open the throttle, the OD will will not disengage. You can eliminate the throttle switch for testing purposes by shorting the two leads together at the switch. In this mode, the OD should disengage whenever you turn off the dash switch regardless of the throttle position.

Put all adjustments back just like you had them .Lever and hole rarely exactky line up , just a good starting point when aligning OK----Keoke-

Keoke,
I realigned everything including reset the throttle switch and I have not been able to get the OD to engage at all. The solonoid works, the lever is aligned with the hole and nothing. Does this mean I have a pressure problem? Is there any other diagnostics I should do? Thanks for all the help and have a good day!

John

You didn't mention checking the operating valve lift after adjusting the clamped on arm on the solenoid side. Maybe you
did but didn't mention it.
Here is the relevant portion from a document that Dave had sent me when I was having o/drive problems. I can email you all of my O/drive info that I have, just PM me.

Ed

5- Operate valve adjustment
a- Set control valve ball lift to .030" to .040". Measure with dial indicator. Cap & spring removed.
Adjust clamped operating arm. Verify movement with the solenoid plunger, not the arm.

I'm confused, John. You said the OD engaged, but then didn't disengage. Now you say it doesn't engage at all. If it engaged at one time and you changed the adjustment, it can't be a pressure problem. It comes back to the solenoid lever adjustment. Even though the OD switch is turned off, if you don't depress the throttle (when the throttle switch is adjusted correctly), the OD will still engage when you shift into 3rd until you depress the throttle sufficiently.

To simplify trouble shooting, take the (damned) throttle switch out of the circuit (put both wires under the same terminal, for the time being).

At this point, only the on/off switch and the 3rd/4th gear selector switch are controlling power to the solenoid.

Try this: switch on the ovd, and if it doesn't energize the solenoid, pull around on the shift lever (while in 3rd or 4th). I've seen the gear selector switch so worn, that you could "downshift" out of ovd (for passing) by just pulling the shift lever towards you (lefthand drive). When you'd release the tension on the lever, it would spring back and the ovd solenoid would energize again.

Ed K,
I would really appreciate your info on trouble shooting the OD. My email is johnprogesscomcast.net (not progress..a common mistake). I did look at the valve lift and it did move. I will measure it today.

Tim,
I have been messing with this thing for a week. I finally got it to engage and disengage several times, then once it did not disengage. I finally got it to work a few more times but now it won't engage after I have reset everything.

Randy,
The solonoid has worked fine through all this. It lifts as it should and rotates the lever arm. The lever arm does not move much, about 1/2 the diameter of the lever arm hole (3/32" or so). I set the throttle switch as per the book and it appears to work fine but I will take it out of the loop and try again today. There is an adjustment under the solonoid valve that seems limit the downward movement, not a rubber pad as in the book and no mention about this adjustment.
The car has just been completed from a 27 month total restoration. Oil level is full and I used 30 wt non detergent oil as per John at Quantum Mechanics. Thanks again for all the help and everyone have a good day!

John

Norman Nock in his Tech Tips on adjusting the solenoid lever says:
1. Loosen adjusting nut.
2. Using a 3/16" drill bit, insert it into the hole on the right side. (This holds the lever in its "on" position)
3. Activate solenoid. (by moving shift lever to right with key on and OD on)
4. Tighten adjusting nut (while solenoid is activated)
5. MAKE SURE THE ARM IS TOUCHING THE ACTUATING FLARE at the bottom of the solenoid plunger (the flat part that lifts the lever. "If this part of the adjustment procedure is not done properly, you are wasting your time because the overdrive will not work!"

Also, Norman says: "the last 1/4" of the solenoid movement is what releases the hydraulic pressure to activate the OD." You should have more travel of the solenoid than 3/32"

Are you still able to actuate the OD manually by pressing down on the right side lever while running in 3rd or 4th gear?
If so, then it continues to be an actuating arm or solenoid travel issue.

Best wishes....

Tim,
If I move the lever on the right side of the tranny by hand I get about .060" movement of the control valve up and down. If I use the solonoid it is only about .010" of up and down movement. I looked at the solonoid lever arm and the vertical clearance between the hook in the lever arm and the sholders on the solonoid is .080" which means that the solonoid moves that much before engaging the lever arm which turns the control rod and hence very small up and down movement of the control valve. I think I will try to shim this and see what happens. I looked at the solonoid and it has about 3/16" total travel. I may have to lower the bottom stop to give more overall solonoid travel. I did not get a chance to drive the car today. The 3/32" of movement I was refering to is the movement of the lever arm on the right side of the tranny with the 3/16" dia. hole. I really appreciate all the help. Thanks and have a good day!

John

Just thought I'd add, if o/d does not disengage, under no circumstances use reverse gear, you almost certainly will damage the unidirectional bearings in the o/d unit. cheers Genos2

Is there anyway you could take a picture of the solenoid and arm at rest? The bottom of the solenoid plunger should be touching the lever arm at rest. There should be no "free-play" between the solenoid plunger platform (the ledge that lifts the lever arm) and the lever arm. You need to be careful about shimming the plunger, it may prevent it from going up far enough to depress the little button at the top of the solenoid that switches the power from high-lifting (20 amps) to low-maintaining power (2 amps). It shouldn't need shims if you do the adjustment correctly.

Remember, you must have the solenoid energized to tighten the adjusting nut, making sure the lever arm (ITEM C) is in contact with the platform of the solenoid plunger (POINT D in the drawing)

This drawing is from Norman Nock.

Hi John,

I just emailed you all of the o/drive doc I had.

If you only have .010 ball lift you need to fix / adjust

to obtain the required .030 - .040 inch valve/ball lift.

Once you get the required lift your o/drive should engage again.

Good luck !

Ed

Tim,
There is no clearance between the lever arm and the bottom of the solonoid plunger. The clearance is at the top of the lever arm. My solonoid plunger is moving about 3/16" and I am wondering if it is enough. I will check again today and see if I can get enough movement.
Ed,
I got your email. I can get plenty of movement in the control valve by moveing the lever arm on the right side of the tranny but not with the solonoid. I will play with it again and use a battery charger to move the solonoid and see what happens. Thanks alot and have a good day!

John

Update: I got the solonoid lever adjusted to give me about .040" lift of the operating valve using the solonoid. I made a fitting that duplicated the plug above the operating valve and allows a pressure gage to be installed. Took the car for a drive and after engaging the OD I got no pressure and needless to say the OD did not work. What is my next step to get pressure? Thanks again and have a good day!

John

Well sound like you may need a new pump!! But check the one way return valve it may be cluttered up with dirt.???--Keoke

Keoke,
I read that this could be the problem. Do you know if this can be done with the tranny in the car. It looks awful tight to get the housing with the solonoid off the tranny. Thanks and have a good day!

John

If memory serves me correctly, the pump can be accessed from the bottom, beneath (or above) the big brass plug.

The later model (>68) MGB overdrives were so much trouble to mate to the back of the trans without jamming up the cam/plunger, that I made up a tool so I could install the pump after the overdrive was attached.

Point is, I'm sure it can be removed, but I don't know if it will be easy. I have an ovd unit on the bench, so I'll make it a point to take a look for you.

The pump can be removed if you don't mind being on the floor with the car on ramps or jack stands. Before you do anything else you should probably make sure the pressure relief valve is not stuck open. As long as you are to the point where you know you need to drain the oil, go ahead and do so. Then remove the side cover from the overdrive (being careful to release the accumulator spring by leaving the rear bolts a little behind the others as you go around). When you get the cover off and look in to where the pump sits you will see the relief valve. It is the same sized cap as on the operating valve. Take it out and see if there is debris or a stuck ball/broken spring etc. You may be able to restore pressure by cleaning this out and putting a new ball bearing in (I got a lifetime supply at Orchard Supply Hardware). If this all looks good you may have a pump problem. With mirrors and flashlights you should be able to see the pump piston go up and down if you turn the transmission mainshaft (which would be a trick from under the car). If the pump piston goes up and down and follows the cam lobe, and the relief valve is good you could still have an accumulator problem. If the pump is not operating normally and you need to pull it out, it is just above the oil screen when you take out the big plug on the bottom. It is withdrawn with a puller that threads into the bottom of the pump. I've got one, but it is possible to make one from a section of pipe a bolt with the proper thread and a little welding. The thing to remember if you do this is that the pump roller attached to the piston can be spun 180 degrees when the pump is removed. If it goes back in like this it can bend the piston rod and you will then have a real problem. The pump can be tapped back into place, but extreme caution is needed to ensure the roller is properly on the cam as you do this (and the relief valve must not be installed before the pump goes back in). You will see that where the roller is pinned is not quite symmetrical. The chances are that if there is a pump problem it pretty much has to be that either the roller is broken and thus not following the cam on the mainshaft, or the piston is bound in the pump body. Obviously if this happens the cam will shove it down and the spring will not have enough expansion force to put the piston roller firmly on the cam. If you need to remove the accumulator it is another post for that. Also not terribly hard to do, but do not remove the piston from the accumulator body unless you know the piston is frozen in place (which would not allow the OD to work, but you could still have pressure (I think). My guess, bad press. relief valve or bad pump. Relief valve easier than pump. Check it first. Laycock-de Normanville...where is Normanville anyway and just who was Laycock?

I had similar problems (loss of pressure). I took off the accumulator cover and removed the accumulator springs and cleaned out the sludge. I also messed around with the ball bearing (that is pushed up by the operating lever/solenoid), put everything back together and it worked fine.

OK that will be my next step. I have spent so many hours under this car in the last 27 months a few more is not going to be a problem! I will have the wife turn the wheels while I watch the pump. When I rebuilt the unit I did replace the accumulator housing but the piston looked fine so I reused it. Might have been a mistake. So from what I understand I should be able to do all this with the tranny in the car, yes? Again thanks for the help and encouragement and have a good day! And by the way I think I mispoke about the OD not disengaging. I think it disengaged ok just not when I flipped the dash switch. The gear selector switch has always worked without a problem.

John

At the risk of my sounding stupid, I must ask if it disengages when you accelerate after turning off (normal) the switch? This is how it is suppose to work.

WHAT!! You telling me: If you turn the OD dash switch off then depress the accelerator pedal and it disengages you are good to go-OK. If OD is engaged only turning OD dash switch off will not cause it to disengage--Keoke--

Naa you be OK!! TH

I did everything with the trans in the car.

To repeat clearly what everyone else is also saying:

The OD will only disengage when you depress the accelerator down somewhat AFTER turning off the OD switch. Turning off the switch will not disengage the OD until you depress the accelerator sufficiently to move the OD throttle switch. The designers only wanted disengagement when under acceleration, not deceleration.

Okay, my overdrive is about half disected, here: http://www.rfdm.com/gallery/album144

Nothing says it better than photos, Randy.

Well I checked the pump and it was moving fine. The non-return valve looked dirty and the ball looked suspecious so I replaced it. I packed the pump with grease and reassembled and adjusted everything and went for a test run. OD would not engage! Went home an put my pressure gage on and no pressure. Drove around a little and noticed that the pressure came up to 225 lb, promising at least. After a little longer low and behold the pressure was up to about 475 lb and the OD seemed to work fine. I am going for a test run this morning and hopefully it will be OK. Thanks and have a good day!

John

Behold, the pump. More pictures at: http://www.rfdm.com/gallery/album144?page=9

Randy,
The seat for the ball bearing in the check valve on your pump looks good in the photo. As I mentioned in pervious posts (other threads) when I pulled mine the seat was badly pitted and I ended up lapping it with a ball bearing glued to a drill mandrel. That fixed one of my problems. Hey, if you could just roll that piston with the roller so that you can show that the two ears of the fork that hold the roller are not of equal thickness, that would point out why you have to pay attention to how it is oriented when you re-install the pump. The main problem I had was that fork was cracked, slightly bending the piston assembly; I think from the po installing the pump 180 degrees out, and it caused the pump piston to jam in the cylinder and not go up and down.

DOH! I just looked at your other photos and you've already got a great shot of the ears.

Just for future reference if needed, how do you orient the "ears" of the pump (what is the reference point) to make sure it is in correctly?

John, I'm glad it seems to be working now. You have shown a lot of perserverence. I also recall that after working on my OD that it took a while for the pressure to return after taking things apart. It may have something to do with getting the pump primed, but I had a similar loss of pressure, then it returned after running for awhile with the top plug off. When oil starting bubbling up, I reinstalled the ball, spring, and plug and its been working perfectly ever since.

I'm not entirely sure of what you're asking...

John was saying you had to orient the pump correctly. I was asking how you know it is oriented correctly. Looking at your new pictures, it appears the thinner ear is under the brass thing. Is that the key? Does the cam go in the brass hole? I suppose it would be obvious if I took it apart, but John said his was in wrong to begin with, so I wondered how you'd know if were right or wrong.

No, right in front if it:



Cruise through this album, and it will probably answer a bunch of your questions. http://www.rfdm.com/gallery/album144

Took the car for a drive and the OD seemed to work fine. I noticed that when I stopped the car the presure was still aroung 400 lbs. I operated the OD solonoid 3 times and it was down to zero lbs. Do people bother to relieve the pressure in the OD or just leave the tranny sit with 400 lbs. pressure? Thanks and have a good day!

John

Good news, John. Don't worry about the oil pressure. It's designed for that. You know only because you have a pressure gauge temporarily attached. Everyone else wouldn't know.