[Healeys] Overdrive pressure

[gradea1 at charter.net]

Simon-I did all of my test readings on the bench-transmission out of
the car. I use an electric drill, in reverse, to drive the yoke and
obtain the readings.
What you describe is a pressure issue in the accumulator. The car will
not shift into OD with low pressure. It needs that high number to
overcome the 8 springs which keep the cone clutch to the rear position
(direct drive). Then as the pump builds up pressure, it is available
when you flip the switch allowing the ball to seat in the
valve.(providing that is seating properly-not bleeding down) That high
pressure drives the two horizontal pistons forward, pushing against,
and compressing, the 8 springs and allowing the cone clutch to now run
to the front position, rotating the annulus and sun gear, thus
effecting OD. 
You do not have enough pressure to do that. The hot oil suggests lower
viscosity, and loss of sealing of the O-rings and piston rings. So
yes, I also think you are looking at a tear down and rebuild of the
accumulator and oil pump parts. 
Contact David at OD Spares and see if he concurs and order the
necessary parts...sounds like its time for that. It would be nice to
have that tunnel back in position and all working normal. Hank 

	-----------------------------------------From:
simon.lachlan at alexarevel.plus.com
To: gradea1 at charter.net
Cc: 
Sent: Wednesday August 4 2021 1:35:48AM
Subject: [Healeys] Overdrive pressure

	Hank, 

	Thank you for that. 

	Actually, it’s all gone pear-shaped! 

	I discussed the OD pressure with Dave at ODSpares…..how high the
pressure went at 1500rpm with and without OD engaged and how long it
took for pressure to drop to zero. He said that re-seating the ball
had fixed it. 

	I took it out for a run down a local motorway and some country roads.
10 miles+/-. On the way to this particular pub- surprise – the OD
behaved well, better than for a while. Popped in and out very briskly.


	I only stayed for 20 minutes or so at the pub, by which time there
must have been a fair old heat transfer from gearbox and engine. It
did worse and worse on the way back. Pressure at 250psi in higher revs
and practically 0 at low revs. Paradoxically would click into OD
nicely but was back to slipping in/out at low revs. 

	I’m feeling my inner Basil Fawlty coning on. I’ll have to strip
it down after all. 

	(It’s a strange feeling…..sitting in the cab with the wheels off
the ground and letting out the clutch. Kept expecting the car to surge
through the workshop wall. Driving down the motorway without the
tunnel cover feels strange too. I do, so far, still have my left hand.
I do occasionally drive with left hand resting on tunnel cover. Not
yesterday!) 

	Any ideas would be appreciated, 

	Simon 

	FROM: gradea1 at charter.net 
SENT: 03 August 2021 18:22
TO: 'simon.lachlan at alexarevel.plus.com' 
CC: 'Healeys' 
SUBJECT: RE: [Healeys] Overdrive pressure   

	Simon-glad you found the problem. That little valve is the whole
control of the pressure and release and dirt is the main offender.   

	What I see on my gauge is pressure over 400-450, then when OD is off.
a steady bleed down to 300, 200, 100 then in a couple of minutes, or
sometimes a bit longer, goes to 0. Its a "slow bleed". Fades as the
oil flows down thru the valve and that tiny hole. Enlarging it will
make the bleed faster and the plugging up with debris harder to
achieve. They recommend a 1MM hole if I remember the readings
correctly, but its a small drilling to allow oil to pass smoothly to
the sump. This is why you don't want 90W gear oil-its to "thick" to
work with the unit, and it also foams up in the annulus. Good 30W (or
20-50) NON detergent oil is best to keep this process working.
(detergents also foam)   

	Possibly a little oxidation or crud gets between the ball and the
seat, and it then needs a smack to reseat the fit. Small thing matter
in this scenario. We all need a smack, now and then, to get with the
program. Regards, Hank 

	----------------------------------------- 

	From: "Simon Lachlan via Healeys"
 To: "Healeys"
 Cc:
 Sent: Monday August 2 2021 1:24:09PM
 Subject: [Healeys] Overdrive pressure  

	David, Hank…..thank you for help and advice. Hank you were just
about on the money. 

	You’ll recall that my OD was slipping in & out at low revs? Of
course you do. 

	I bought a gauge from ODSpares, excellent people/very helpful. (In
retrospect, I wonder how I’ve managed for so long without one). 

	Pressure showed as well into the 470 to 490 range whilst OD was
engaged at +/- 1,500 rpm in 4th. Which is GOOD. 

	But, pressure dropped to zero immediately upon disengaging and
switching off. Which is BAD. 

	The little hole in the so-called “Valve operating” was/is clear. 

	I phoned Dave Twigger at ODSpares who said that there was debris
under the ball on the seat there OR, if it was clear, then the ball
needed reseating. 

	So, I gave the ball a few brisk taps and the pressure drop did slow a
little up on the next gauge test. 

	I gave it some more taps and it improved somewhat again. Now takes
about 30 seconds to get down to, say, 20psi and then loses pressure
quite slowly. 

	So:- 

	* How hard can one “Tap” the ball? Not the easiest question to
answer, I do appreciate that. One man’s tap is another man’s
wallop?

	I suspect I’ll have to repeat the process…… 

	* What time duration is acceptable in operating terms for the
pressure drop? What am I aiming at?

	 Thanks, Simon
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