[Healeys] FW: RE: Overdrive pressure not releasing.

[gradea1 at charter.net]

One other thing you could do before having to yank out the unit. Drain
the oil, remove the operating valve, and the relief valve, and blow
some air from the plug fitting using a rubber tipped blow gun,
throughout the unit. It may make an oil mess, but not as much a mess
as having to pull the transmission. This might possibly dislodge any
debris blockage in the passages. If you reuse the same oil, strain it
thru a good sieve and look for debris.
Then be especially careful when refilling the gearbox and OD as to not
get any dirt into the opening. Be sure to check the screen and clean
it with kerosene (paraffin) upon assembly. Hank

	-----------------------------------------From: gradea1 at charter.net
To: "simon.lachlan at alexarevel.plus.com"
Cc: 
Sent: Saturday April 16 2022 12:12:34PM
Subject: RE: [Healeys] Overdrive pressure not releasing.

 Hi Simon- I'm sure you read and re-read the chapter G pg. 5
paragraphs in the service manual. The fact that you have 500lbs of
pressure is good, but then the notation of the pressure not releasing,
indicates some kind of blockage in the oil passages that will not let
the pressure drain. 
 Of course, dirt is the most common culprit. That is also why the book
suggests lintless rags...the smallest amount of debris can plug up
these tiny drillings and prevent pressure from draining. One rebuilder
I discuss these finicky ODs with, suggests enlarging the drain hole in
the operating valve body to 1mm. The other key item to check is the
two relief valve springs (ill. 16 & 56 on plate G2). If reversed they
will cause havoc with the pressure drain. If the accumulator is
stuck-not moving-it will hold the pressure as it must move past a
small drilling in the body to release it. That is a physical issue
with the O-rings, or piston rings in that bore. 
 Actually, removing the plug from the operating valve with 500 lbs of
pressure should have shot out the spring, ball and shaft. Since it
dribbled out, the blockage must be further down the pike. Operating
the lever multiple times before removing the plug is to meant release
that pressure. 
 If it has 500 lbs. of pressure, it is in OD! That pressure pushes the
two pistons (#11) toward the front of the trans compressing the 8
clutch springs and placing the clutch facing into contact with the sun
gear. 
 Trusting that OD spares properly reassembled the unit would be most
logical, but maybe not. I think the answer is still with them, and
unfortunately you would have to bring them the unit (5th pull!) The
problem does not appear to be electrics/adjustment related. Regards,
Hank

	----------------------------------------- From: "Simon Lachlan via
Healeys"
 To: "Healeys"
 Cc:
 Sent: Saturday April 16 2022 10:20:09AM
 Subject: [Healeys] Overdrive pressure not releasing.

	My OD is driving me mad and I definitely need some inspired advice. A
bit of background first. I’ll try to lay out all the facts in a
logical sequence. (I’m increasingly reluctant to link ODs with
logic!) 

	* I’d say that the OD has done +/- 15k miles since a total rebuild
by Overdrive Spares here in UK.
 	* The OD had issues before Christmas (21) and was sorted out by OD
Spares. The accumulator was uprated and pressure issues sorted.
 	* OD functioned 100% on the few times I’d been able to take it out
since then until..
 	* One day, the OD stopped functioning.
 	* I checked the electrics. All fine there so I delved a bit deeper.
 	* It had fried its solenoid which I replaced. But…
 	* That did not fix the problem so…
 	* I decided that the operating valve’s adjustment might be off
so..
 	* I bought a dial gauge and hoped to sort it out precisely rather
than by “feel”, which I lack in this area.
 	* Prior to using the gauge I decided to see if the OD was
functioning at all so I raised the car on stands and fitted my
pressure gauge.
 	* I get a reading of 500psi rising a bit when I rev the engine but
I’d suppose that would drop when the oil warms up.
 	* BUT, and this is where things go pear-shaped…moving the little
lever on the RHS up and down does not engage/disengage OD. There is no
change on the gauge to show OD engaging or disengaging.
 	* AND, the gauge stays at 500psi even when the engine is off. Moving
the lever 20 times has zero effect. Stayed at 500 overnight!
 	* Of course, I checked for dirt in the operating valve area. None.
 	* Likewise, the tiny hole in the “valve – operating” (the
spindle thing which the ball sits on)….that’s clear. And surely,
the pressure would diminish overnight if something in that area was
partially obstructed?
 	* When I remove the pressure valve, there’s a small spillage –
no more than you’d expect – but repeating the pressure gauge
process only returns the same results.
 	* I see in the bible according to Norman Nock that “Holding this
lever with your thumb and index finger, you should be able to push the
lever down lightly about ⅜” until you feel a slight spring
pressure resistance. The lever should go down another ¼” after
encountering the resistance……” ie there’s about ⅝”
movement up & down in that lever. Well, my lever does move and does
lift the ball, but there’s not ⅝” movement there. Could that be
the problem area???
 	* Almost finished…keep reading!

	So, I’m stumped. Every time I learn something new about the OD, it
has a new trick to baffle me. 

	I’ve no 100% sure way of telling whether it’s gone into OD and
stuck there or whether it’s simply not going into OD at all. 

	I’ve done a lot of reading through my books and collection of
advice from the various gurus and found reference to ODs being stuck
but those seemed to be to do with “weak springs” which,
particularly after a long lay-off, wouldn’t disengage. The cure for
this being a good smack on the steel plate sandwiched in the OD from
below. Well, that seems to be a stuck mechanism issue whereas I’m
facing a hydraulic conundrum. Or am I? 

	There is what is usually referred to as the “pressure relief
valve” adjacent to the accumulator. The name suggested that pressure
might be stuck in that area….but surely not overnight? 

	Any ideas? I am particularly reluctant to take the gearbox and OD
out. You’ll recall the ridiculous business of the defective clutch
kit? Well, I forget whether we had the box in and out 3 times or 4.
I’d hoped not to do it again so soon or ever for that matter. 

	I’m hoping for a miracle of course but some sound advice would be a
godsend………… 

	Thanks, 

	Simon 

	
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