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Overdrive In-Op AH BJ8 1967

mmgwhite

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Hello all
I have an inop overdrive on my Healey. I have satisfied myself all of the electrical components are
functioning correctly.. It used to work flawlessly then slowly became less reliable, now no joy.
I have found a different set-up under the plunger on the solenoid. The manual calls for a small rubber bumper "stop (rubber)". Part number 27 in the drawing. Mine has a stud with a nut on it. Doesn't look adjustable. I cant find anything like it in the manual. I left the nut off for better view of the stud. Should that rubber bumper be where the stud is??
Anybody have suggestions on how to proceed in adjusting the throw of the solenoid with this finding .
Thanks
Matison
See attached pictures.

overdrive.JPGoverdrive4.JPGoverdrive3.JPG
 

Keoke

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Anybody have suggestions on how to proceed in adjusting the throw of the solenoid with this finding .

Matison:
Obtain a replacement "Rubber Stop" and install it.

Testing of the OD unit can be done after the tranny tunnel is removed by manually pulling lever # 13 0n the drawing up,while the differential is jacked up. the OD should function.
 
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mmgwhite

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I managed to find an Allen wrench port on the bottom of the housing. Got the threaded post out.
It has a rounded top like it was intended to come in contact with the solenoid plunger and is clearly adjustable.
Anybody else seen this configuration?
MatIMG_0137.JPG
 

BJ8Healeys

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My overdrive unit also had the stud and nut instead of the rubber bumper. I noted that the solenoid plunger had a fairly deep dent in it where it had been contacting the stud as the plunger relaxed.

Unfortunately, it has been too many years since I discovered this issue and I cannot remember what, if anything, I did about it, although I may have adjusted the nut to be flush with the end of the stud to avoid making the dent deeper. While trying to refresh my memory, I reviewed the overdrive rebuild video posted by Magnus Karlsson here: [FONT=&quot]https://healeyspecialists.com/videos/

[/FONT]The overdrive unit he is working on in the video also has the stud and nut. BMC was very casual about updating such details in the parts manual when they implemented them. Evidence indicates to me that the stud and nut replaced the rubber bumper.

What is important about the motion of the solenoid lever is that it raises the operating valve steel ball at least 1/32" off its seat when the solenoid operates. As Magnus mentions in his video, the setting of the lever using the lever on the opposite side (the one with the small hole in the end that is lined up with a corresponding hole in the overdrive housing) is sometimes not accurate enough. I used a dial indicator to verify that the operating valve came up 1/32" when the solenoid was energized.
 

BJ8Healeys

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Hello all
I have an inop overdrive on my Healey. I have satisfied myself all of the electrical components are
functioning correctly.. It used to work flawlessly then slowly became less reliable, now no joy.

If the overdrive performance slowly declined, then you may have an oil pressure problem. This could be due to steel wear particles scratching/scoring the aluminum accumulator walls so that the accumulator can't build sufficient pressure, broken accumulator piston rings, leaky O-rings on the operating pistons, plugged operating valve --- all problems I have had with my overdrive (except for the last one). Before you go too far into making adjustments, you really should acquire a pressure gauge to measure the operating pressure. Before rebuild, with a slow shift into overdrive I was getting pressure of about 350 psi down to 100 psi when the dash switch was turned on, with the pressure going back to 350 - 365 after the shift. After rebuilding the O/D, I got a pressure of 450 psi and dropping to about 250 psi during shift. [FONT=&quot][/FONT]

[FONT=&quot][/FONT]
 
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mmgwhite

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Thanks all
That explains my findings. Now to see if I can work some magic.
Steve mentioned pressure problems. Just so happens I found some metal filings in the transmission oil at last change.
Perhaps some metal found its way into the accumulator.
I have checked the operation ball valve and found it clean.
Mat
 

RAC68

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Hi Mat,

I must admit, I was not aware of the metal screw-in solenoid bumper as I have the rubber type. Low internal pressure can be caused by a number of conditions with particulate scoring being one of the more drastic. Since this unit has been used in many British cars of the era and manufacturer recommendations have suggested everything from Automatic Transmission Fluid, Gear Oil, and (in our case) 30Wt non-detergent, it stands to reason that trying a fresh fill of your chosen oil could help clean the unit of much of the contaminants. Keep in mind that the 30Wt Non-Detergent oil was used to allow any metal particles fall out of suspension and be drawn to the magnetic drain for removal. Those using detergent oils (all multi-weight oils are detergent oils) are using a fluid designed to keep these particles in suspension and extraction by a filter...something our O/D and transmissions do not have.

You mentioned you experienced a deterioration in operation over a period of time. How long did this deterioration take place?

Take a look at the size and quantity of metal chards found in the oil. It is not uncommon to find some particles of metal as a result of normal ware, however, higher quantities of particles of coarser and larger configurations could indicate a more aggressive component failure.

Before taking anything apart, I would install new fluid, adjust and verify the solenoid is functioning (possibly using Keoke's suggestion), and re-drain the unit and carefully examine any foreign contents.

The O/D and transmission are quite robust and well tested units with most issues being electrical (connections and/or components). Although you have indicated that you do not have an electrical problem, I would recheck both component and wiring for any potential faults as the interdependence in this circuit is quite high.

All the best,
Ray(64BJ8P1)
 
Last edited:

Patrick67BJ8

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The solenoids are often heard to click and most people think they are working when in fact they aren't. It takes quite a bit of electricity to pull down the solenoids to engage the overdrive but once they are engaged the holding coil power is very small.
 
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mmgwhite

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How does one test the internal pressure?
I have watched the U tube videos but can't tell where they are attaching the pressure gauge.
Guessing it must be on the port containing the spring, post and ball that the solenoid opens.
Also, new interesting finding. The end of the oil dipstick in the transmission looks like it was nipped off by something
Is it possible for it to get into the internal gears if installed wrong or something? Maybe that is where my metal came from?
Mat
 

Healey Nut

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Have you pulled and checked the OD filter screen ?
Yes the pressure is measured at the plunger plug hole so you ned a spare plug with an adaptor on it with a gauge .
Most OD issues are due to incorrect set up . The ball plunger must lift a specific distance which can be measured with a DTI or a caliper .
I would suggest you use the search feature on here for OD engagement issues and grab a few cold ones , happy reading .
 

BJ8Healeys

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How does one test the internal pressure?
I have watched the U tube videos but can't tell where they are attaching the pressure gauge.
Guessing it must be on the port containing the spring, post and ball that the solenoid opens.
Also, new interesting finding. The end of the oil dipstick in the transmission looks like it was nipped off by something
Is it possible for it to get into the internal gears if installed wrong or something? Maybe that is where my metal came from?
Mat

You need a pressure gauge that can read beyond 500 psi, and it helps to be liquid-filled to dampen gauge needle vibrations. I bought one from this source for $56 in 2013: jholekamp@sbcglobal.net
It comes complete with all adapters and connections necessary to check the O/D operating pressure. All you have to do is remove the plug from the metering pin chamber and screw in the gauge.

The end of my gearbox oil dipstick also looks like it was ground off on the tip. It was like that the first time I ever checked the oil (back in 1984), and it's still that way and not getting worse. No idea whether something caused it or it was just made that way.
 

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bighealeysource

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Hey Mat,
Two great sources to check out on our OD units. Google Buckeye Triumphs, an Ohio Triumph club, as they have a fantastic article on their website you can download about the Laycock overdrive which was also used on Triumph's. Best one I have seen. Other would be go to Youtube and search "rebuilding an Austin Healey overdrive" and you'll find a nice long video from a gentleman from Norway/Sweden I think rebuilding a Healey od unit. It's in English so no problem understanding it.

Also agree with Keoke about testing to see if it still works. As has been recommended, fill it back up with 30 or 40 wt ND oil, and with trans tunnel off - I know, a huge pain - put her on jackstands or you can even take it out on the road - watch that driveshaft !!! - and manually push on the lever on the right side. You will at least find out if it works when engaged. If it does not work, then the above article or video should help you get it back to running. If it was a gradual thing where eventually just stopped working, I would doubt it is a major problem, either adjustment or pressure. I got one of the pressure rigs like Steve recommended and that is what you need to check the pressure. Should still be available as got mine last year.

Regards
Mike
 
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