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Sounds to me like your hydraulics are OK; sounds more electrical to me.
I had similar symptoms with an intermittent OD relay; I fixed it in a
hotel room in Canada by opening up the relay and filing the points (and
replaced it when I got home).
I suspect--and it's only a guess--that you get the drop out/in symptom
at lower revs because most of us--racers aside--spend the vast majority
of time cruising at 2-2.5K RPM, so you get that symptom in that regimen
more often.
Bob
On 7/30/2021 10:04 AM, Henry G Leach via Healeys wrote:
> Simon-yes, there are two balls which control the pressure in the unit.
> In the operating valve which is engaged by the action of the solenoid,
> dirt is a possible issue. There is a very tiny hole drilling in the
> stem of the valve which allows the oil to circulate. That opening can
> plug with debris and stop the flow. Oil from the accumulator goes thru
> this valve and lifts the ball allowing the operating cylinders to move
> forward on the clutch producing the overdrive. When the ball is seated
> (solenoid off) oil does not pass and is dumped into the OD sump.
>
> You can see that this tiny drilling is very important and must be kept
> clear. Often rebuilders suggest to enlarge the hole to 1MM. It may
> change the dwell time of the OD action, but its has a better chance of
> staying clean...a theory not proven.
>
> The other ball is on the oil pump and that is the one that Del
> suggested needed a new spring or extended plunger to enhance
> pressure-another theory.
>
> As you measured no pressure when out of OD, that is due to the ball
> properly seating on the valve and reliving the pressure that operates
> the two pistons. If you move the lever or engage the solenoid you
> should get 470 lbs. again.
>
> I would suggest cleaning the valve-use a magnet to get the parts out
> and don't use a shop rage to clean them (no lint). If all is ok in the
> valve body you need to look further into the accumulator and o-rings
> and piston rings. I suggest you contact David at OD Spares for some
> additional advise. Hank
>
> -----------------------------------------
>
> From: "Simon Lachlan via Healeys"
> To: "Healeys"
> Cc:
> Sent: Friday July 30 2021 7:32:48AM
> Subject: [Healeys] Overdrive pressure drop
>
> Hi,
>
> Iâ??ve been having issues with my OD. Similar to someone else quite
> recently��
>
> The OD would engage and disengage properly at high revs but once the
> car was cruising along at low revs, the OD would somehow act like it
> was on the verge of dropping out &/or dropping back in.
>
> It /may/ be electrical, but I doubt it. The solenoid goes in with a
> nice robust click.
>
> I was thinking that it would be pressure related. So�����
>
> Iâ??ve bought a gauge from OD Spares here in UK and got the car up on
> axle stands.
>
> I did the test procedure much per the Del Border article which I sent
> out the other day.
>
> 1. Pressure is good, at the top end of 470 to 490 with gearbox oil
> cold. ie 470 to 490 psi at 1500 rpm in 4^th and then same in 4thOD
> after a momentary drop. (40wt non-detergent).
> 2. When I go out of OD, brake and switch off, the pressure drops to
> nil at once. Which is, apparently and according to the article, WRONG.
>
> I am now leaning towards something in the so-called â??ball valveâ??,
> items 33 to 37 on page 2 of attached.
>
> Does the above seem like a good place to start?
>
> Could, say, a worn spring or a piece of dirt in that area cause these
> issues?
>
> The names of these valves, â??Operating valveâ?? at top and â??Ball valveâ??
> at bottom seems to vary with every article I read.
>
> The â??non-return valveâ?? and the â??check valveâ??â?¦.are these the same
> thing
> and are they what BMC calls the â??Ball valveâ??, item 37.
>
> Thanks, hopefully!
>
> Simon
>
>
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Sounds to me like your hydraulics are OK; sounds more electrical to
me. I had similar symptoms with an intermittent OD relay; I fixed it
in a hotel room in Canada by opening up the relay and filing the
points (and replaced it when I got home).<br>
<br>
I suspect--and it's only a guess--that you get the drop out/in
symptom at lower revs because most of us--racers aside--spend the
vast majority of time cruising at 2-2.5K RPM, so you get that
symptom in that regimen more often.<br>
<br>
Bob<br>
<br>
<div class="moz-cite-prefix">On 7/30/2021 10:04 AM, Henry G Leach
via Healeys wrote:<br>
</div>
<blockquote type="cite"
cite="mid:32d7457e41365c17ea022d3f0294c0dbfb69d112@webmail">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
Simon-yes, there are two balls which control the pressure in the
unit. In the operating valve which is engaged by the action of the
solenoid, dirt is a possible issue. There is a very tiny hole
drilling in the stem of the valve which allows the oil to
circulate. That opening can plug with debris and stop the flow.
Oil from the accumulator goes thru this valve and lifts the ball
allowing the operating cylinders to move forward on the clutch
producing the overdrive. When the ball is seated (solenoid off)
oil does not pass and is dumped into the OD sump.
<div><br>
</div>
<div>You can see that this tiny drilling is very important and
must be kept clear. Often rebuilders suggest to enlarge the
hole to 1MM. It may change the dwell time of the OD action, but
its has a better chance of staying clean...a theory not proven.</div>
<div><br>
</div>
<div>The other ball is on the oil pump and that is the one that
Del suggested needed a new spring or extended plunger to
enhance pressure-another theory.</div>
<div><br>
</div>
<div>As you measured no pressure when out of OD, that is due to
the ball properly seating on the valve and reliving the pressure
that operates the two pistons. If you move the lever or engage
the solenoid you should get 470 lbs. again.</div>
<div><br>
</div>
<div>I would suggest cleaning the valve-use a magnet to get the
parts out and don't use a shop rage to clean them (no lint). If
all is ok in the valve body you need to look further into the
accumulator and o-rings and piston rings. I suggest you contact
David at OD Spares for some additional advise. Hank<br>
<br>
<p>-----------------------------------------</p>
From: "Simon Lachlan via Healeys" <healeys@autox.team.net><br>
To: "Healeys"<br>
Cc: <br>
Sent: Friday July 30 2021 7:32:48AM<br>
Subject: [Healeys] Overdrive pressure drop<br>
<br>
<div class="WordSection1">
<p class="MsoNormal">Hi,</p>
<p class="MsoNormal">Iâ??ve been having issues with my OD.
Similar to
someone else quite recently��</p>
<p class="MsoNormal">The OD would engage and disengage
properly at
high revs but once the car was cruising along at low revs,
the OD
would somehow act like it was on the verge of dropping out
&/or
dropping back in.</p>
<p class="MsoNormal">It <i>may</i> be electrical, but I
doubt it.
The solenoid goes in with a nice robust click.</p>
<p class="MsoNormal">Â </p>
<p class="MsoNormal">I was thinking that it would be
pressure
related. So�����</p>
<p class="MsoNormal">Iâ??ve bought a gauge from OD Spares here
in UK
and got the car up on axle stands.</p>
<p class="MsoNormal">Â </p>
<p class="MsoNormal">I did the test procedure much per the
Del
Border article which I sent out the other day.</p>
<ol style="margin-top:0cm;" type="1" start="1">
<li class="MsoListParagraph" style="margin-left:0cm;">Pressure
is good, at the
top end of 470 to 490 with gearbox oil cold. ie 470 to
490 psi at
1500 rpm in 4<sup>th</sup> and then same in 4thOD after
a momentary
drop. (40wt non-detergent).</li>
<li class="MsoListParagraph" style="margin-left:0cm;">When
I go out of OD,
brake and switch off, the pressure drops to nil at once.
Which is,
apparently and according to the article, WRONG.</li>
</ol>
<p class="MsoNormal">I am now leaning towards something in
the
so-called â??ball valveâ??, items 33 to 37 on page 2 of
attached.</p>
<p class="MsoNormal">Â </p>
<p class="MsoNormal">Does the above seem like a good place
to
start?</p>
<p class="MsoNormal">Could, say, a worn spring or a piece of
dirt
in that area cause these issues?</p>
<p class="MsoNormal">Â </p>
<p class="MsoNormal">The names of these valves, â??Operating
valveâ??
at top and â??Ball valveâ?? at bottom seems to vary with every
article
I read.</p>
<p class="MsoNormal">The â??non-return valveâ?? and the â??check
valveâ??â?¦.are these the same thing and are they what BMC
calls the
â??Ball valveâ??, item 37.</p>
<p class="MsoNormal">Â </p>
<p class="MsoNormal">Thanks, hopefully!</p>
<p class="MsoNormal">Simon</p>
<p class="MsoNormal">Â </p>
<br>
</div>
</healeys@autox.team.net></div>
</blockquote>
<br>
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