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Simon-yes, there are two balls which control the pressure in the unit.=
=0AIn the operating valve which is engaged by the action of the solenoid=
,=0Adirt is a possible issue. There is a very tiny hole drilling in the=
=0Astem of the valve which allows the oil to circulate. That opening can=
=0Aplug with debris and stop the flow. Oil from the accumulator goes thr=
u=0Athis valve and lifts the ball allowing the operating cylinders to mo=
ve=0Aforward on the clutch producing the overdrive. When the ball is sea=
ted=0A(solenoid off) oil does not pass and is dumped into the OD sump.=
=0AYou can see that this tiny drilling is very important and must be kep=
t=0Aclear. Often rebuilders suggest to enlarge the hole to 1MM. It may=
=0Achange the dwell time of the OD action, but its has a better chance o=
f=0Astaying clean...a theory not proven.=0AThe other ball is on the oil=
pump and that is the one that Del=0Asuggested needed a new spring or ex=
tended plunger to enhance=0Apressure-another theory.=0AAs you measured n=
o pressure when out of OD, that is due to the ball=0Aproperly seating on=
the valve and reliving the pressure that operates=0Athe two pistons. If=
you move the lever or engage the solenoid you=0Ashould get 470 lbs. aga=
in.=0AI would suggest cleaning the valve-use a magnet to get the parts o=
ut=0Aand don't use a shop rage to clean them (no lint). If all is ok in=
the=0Avalve body you need to look further into the accumulator and o-ri=
ngs=0Aand piston rings. I suggest you contact David at OD Spares for som=
e=0Aadditional advise. Hank=0A=0A=09------------------------------------=
-----From: "Simon Lachlan via=0AHealeys" =0ATo: "Healeys"=0ACc: =0ASent:=
Friday July 30 2021 7:32:48AM=0ASubject: [Healeys] Overdrive pressure d=
rop=0A=0A=09Hi, =0A=0A=09I=E2=80=99ve been having issues with my OD. Sim=
ilar to someone else quite=0Arecently=E2=80=A6=E2=80=A6 =0A=0A=09The OD=
would engage and disengage properly at high revs but once the=0Acar was=
cruising along at low revs, the OD would somehow act like it=0Awas on t=
he verge of dropping out &/or dropping back in. =0A=0A=09It _may_ be ele=
ctrical, but I doubt it. The solenoid goes in with a=0Anice robust click=
. =0A=0A=09I was thinking that it would be pressure related. So=E2=80=A6=
=E2=80=A6=E2=80=A6=E2=80=A6=E2=80=A6 =0A=0A=09I=E2=80=99ve bought a gaug=
e from OD Spares here in UK and got the car up on=0Aaxle stands. =0A=0A=
=09I did the test procedure much per the Del Border article which I sent=
=0Aout the other day. =0A=0A=09* Pressure is good, at the top end of 470=
to 490 with gearbox oil=0Acold. ie 470 to 490 psi at 1500 rpm in 4th an=
d then same in 4thOD=0Aafter a momentary drop. (40wt non-detergent).=0A=
=09* When I go out of OD, brake and switch off, the pressure drops to=
=0Anil at once. Which is, apparently and according to the article, WRONG=
.=0A=0A=09I am now leaning towards something in the so-called =E2=80=9Cb=
all valve=E2=80=9D,=0Aitems 33 to 37 on page 2 of attached. =0A=0A=09Doe=
s the above seem like a good place to start? =0A=0A=09Could, say, a worn=
spring or a piece of dirt in that area cause these=0Aissues? =0A=0A=09T=
he names of these valves, =E2=80=9COperating valve=E2=80=9D at top and=
=E2=80=9CBall=0Avalve=E2=80=9D at bottom seems to vary with every artic=
le I read. =0A=0A=09The =E2=80=9Cnon-return valve=E2=80=9D and the =E2=
=80=9Ccheck valve=E2=80=9D=E2=80=A6.are these the=0Asame thing and are t=
hey what BMC calls the =E2=80=9CBall valve=E2=80=9D, item 37. =0A=0A=09T=
hanks, hopefully! =0A=0A=09Simon =0A=0A=09
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<html><body>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 accumulato=
r goes thru this valve and lifts the ball allowing the operating cylinde=
rs 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 su=
mp.<div><br></div><div>You can see that this tiny drilling is very impor=
tant and must be kept clear. Often rebuilders suggest to enlarge t=
he hole to 1MM. It may change the dwell time of the OD action, but its h=
as 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 D=
el suggested needed a new spring or extended plunger to enhance pr=
essure-another theory.</div><div><br></div><div>As you measured no press=
ure when out of OD, that is due to the ball properly seating on the valv=
e and reliving the pressure that operates the two pistons. If you move t=
he 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 t=
he parts out and don't use a shop rage to clean them (no lint). If all i=
s 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><div class=3D"reply-new-signature">=
</div><p>-----------------------------------------</p>From: "Simon Lachl=
an via Healeys" <healeys@autox.team.net><br>To: "Healeys"<br>Cc: <br>Sen=
t: Friday July 30 2021 7:32:48AM<br>Subject: [Healeys] Overdrive pressur=
e drop<br><br>=0A<div class=3D"WordSection1">=0A<p class=3D"MsoNormal">H=
i,</p>=0A<p class=3D"MsoNormal">I=E2=80=99ve been having issues with my=
OD. Similar to=0Asomeone else quite recently=E2=80=A6=E2=80=A6</p>=0A<p=
class=3D"MsoNormal">The OD would engage and disengage properly at=0Ahig=
h revs but once the car was cruising along at low revs, the OD=0Awould s=
omehow act like it was on the verge of dropping out &/or=0Adropping=
back in.</p>=0A<p class=3D"MsoNormal">It <i>may</i> be electrical, but=
I doubt it.=0AThe solenoid goes in with a nice robust click.</p>=0A<p c=
lass=3D"MsoNormal"> </p>=0A<p class=3D"MsoNormal">I was thinking th=
at it would be pressure=0Arelated. So=E2=80=A6=E2=80=A6=E2=80=A6=E2=80=
=A6=E2=80=A6</p>=0A<p class=3D"MsoNormal">I=E2=80=99ve bought a gauge fr=
om OD Spares here in UK=0Aand got the car up on axle stands.</p>=0A<p cl=
ass=3D"MsoNormal"> </p>=0A<p class=3D"MsoNormal">I did the test pro=
cedure much per the Del=0ABorder article which I sent out the other day.=
</p>=0A<ol style=3D"margin-top:0cm;" start=3D"1" type=3D"1"><li class=3D=
"MsoListParagraph" style=3D"margin-left:0cm;">Pressure is good, at the=
=0Atop end of 470 to 490 with gearbox oil cold. ie 470 to 490 psi at=0A1=
500 rpm in 4<sup>th</sup> and then same in 4thOD after a momentary=0Adro=
p. (40wt non-detergent).</li>=0A<li class=3D"MsoListParagraph" style=3D"=
margin-left:0cm;">When I go out of OD,=0Abrake and switch off, the press=
ure drops to nil at once. Which is,=0Aapparently and according to the ar=
ticle, WRONG.</li>=0A</ol><p class=3D"MsoNormal">I am now leaning toward=
s something in the=0Aso-called =E2=80=9Cball valve=E2=80=9D, items 33 to=
37 on page 2 of attached.</p>=0A<p class=3D"MsoNormal"> </p>=0A<p=
class=3D"MsoNormal">Does the above seem like a good place to=0Astart?</=
p>=0A<p class=3D"MsoNormal">Could, say, a worn spring or a piece of dirt=
=0Ain that area cause these issues?</p>=0A<p class=3D"MsoNormal"> <=
/p>=0A<p class=3D"MsoNormal">The names of these valves, =E2=80=9COperati=
ng valve=E2=80=9D=0Aat top and =E2=80=9CBall valve=E2=80=9D at bottom se=
ems to vary with every article=0AI read.</p>=0A<p class=3D"MsoNormal">Th=
e =E2=80=9Cnon-return valve=E2=80=9D and the =E2=80=9Ccheck=0Avalve=E2=
=80=9D=E2=80=A6.are these the same thing and are they what BMC calls the=
=0A=E2=80=9CBall valve=E2=80=9D, item 37.</p>=0A<p class=3D"MsoNormal">&=
nbsp;</p>=0A<p class=3D"MsoNormal">Thanks, hopefully!</p>=0A<p class=3D"=
MsoNormal">Simon</p>=0A<p class=3D"MsoNormal"> </p>=0A<p class=3D"M=
soNormal"> </p>=0A</div>=0A</healeys@autox.team.net></div></body></=
html>
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