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Disclaimer: I'm not an O/D expert, having rebuilt exactly one with
reasonable success, but I can throw guesses around.
I think /something/ with the operating valve and its lifting rod
(bent?), but there's couple theoretical causes:
- Too much wear on the cone clutch, causing it to stick in the brake
ring, but the guys at ODSpares would surely have noticed and
replaced/relined the clutch, no?
- Something wrong with the operating pistons (one or both), not allowing
them to recede in their bores when pressure is relieved (O-ring or steel
rings?)
I don't know enough about the intricacies of the internal passageways,
but I do know the accumulator regulates pressure pretty simply: when the
spring is compressed far enough a drain hole is uncovered (not unlike
how engine oil pressure is limited). If that relief hole was somehow
blocked pressure would increase until something gave (like your gauge).
An owner had a similar problem, reported on another forum. Someone
suggested the unidirectional clutch getting stuck, but I can't wrap my
head around that one (I think that would cause issues on overrun,
possibly damaging the O/D).
So, the unit works fine on the test rig, but locks up first time you
engage it and stays there? May be a clue in there somewhere but, so far,
I'm coming up empty.
BTW, did you use the newer accumulator type, with an 0-ring instead of
steel rings?
On 6/18/2022 3:17 AM, simon.lachlan@alexarevel.plus.com wrote:
>
> This saga started months ago and you may remember the case and the
> various suggestions made at the time. Iâ??ve been away and thus unable
> to get back to the problemâ?¦.
>
> The background was that the thing would go into OD but not come out.
> And, after many vicissitudesâ?¦removing box and OD in order to drive it
> up north 3(!) times, it is still playing up.
>
> I shall try to give all the details and background but that will
> entail my being as verbose as usual.
>
> 1. It is in a MKII BT7 centre shift.
> 2. It has, yesterday, new 30 wt non-detergent. Plenty of it. Clean.
> 3. Its electrics pass muster though I wish I could detect a fault
> there so that I could fix itâ?¦. If the ignition is /on /and the
> engine is /off/, when I put the stick in 4^th and engage OD I get
> a nice click and the little lever moves. When I move the lever
> across to 1^st and 2^nd , another click and slight movement on the
> little lever. When I leave it in 4^th but switch the OD /off, /it
> stays engaged until I depress the accelerator a little and then it
> drops out of OD. To my mind at least, this indicates that the
> electrics are working. IS THAT PRESUMPTION CORRECT? I tried it
> with a spare, rebuilt, relay but no dice.
> 4. There is nothing in the little hole and the ball seats nicely. All
> new parts in there.
> 5. The lever is free to move when the ignition is off ie nothing in
> there is slowing the leverâ??s freedom to move as pulled by the
> solenoid.
>
> I have a (new) gauge and it goes up to 500+ psi when in 3^rd or 4^th
> and stays there until I engage the OD. Pressure drops momentarily then
> returns to 500+. All well and good. But it wonâ??t come outâ?¦.
>
> My feeling, going somewhat against received/informed advice, was that
> â??something was stuck inside and not releasingâ??. This was borne out
> when, with the back wheels off the ground, I was trying to find out
> what was going wrong��the gauge was in and I was watching it. Into
> OD��.the usual click plus a different sort of noise/clunk and a
> distinct jerk. The gauge went off the scaleâ?¦.needle all the way round
> and jammed on the reverse side of zero where it remained; gauge
> destroyed. The gasket between the solenoid/operating lever casing and
> the accumulator area ruptured and oil started to come out. Fairly
> briskly. So that was a complete disaster.
>
> I rang up ODSpares, for the 400^th time, and Dave said that the
> accumulator â?? brand new, fitted by them - must have jammed. He, very
> reasonably I thought, said that if I brought the box and OD up
> /again(!)/, heâ??d fit on a complete new unit. So, I did and he did. I
> imagine that he fitted a casing with all new bits where needed. He
> runs them on a rig for 8 hours before letting them leave the shop��
>
> Anyhow, I stuck the box etc back in â?? Iâ??m getting quite good at that
> now â?? and had high hopes. But, no good. The needle goes up to 500+ and
> stays there until I move it in and out of OD by moving the stick left
> to right with the ignition on and the engine off.
>
> Logically, if logic applies to an OD, one might suppose EITHER that
> there is a batch of dud accumulators out there OR that there is some
> external factor that Iâ??ve missed which has been lurking undetected all
> the while?!? BUT, that would not have made the accumulator jam??
>
> Is it possible that there is something extraneous that could cause the
> electrics to play up only when the engine is running?
>
> Or, do ODs need a few miles on them before they start working
> properly? Clutching at straws here!!
>
> One last thing, Dave agreed that there was still a pressure issue. He
> suggested drilling out the little hole in the so-called â??valve â??
> operatingâ?? (the rod under the ball bearing). That was to allow the
> pressure to bleed off faster. He sent me a new rod in case that didnâ??t
> work. Which it didnâ??t! The hole was just a tiny fraction less than 1mm
> and I drilled it out to 1.5mm. (Apparently, the factory used to drill
> them out for competition vehiclesâ?¦)
>
> Anyhow, Iâ??m stuck. As is the OD!. And Iâ??ve gone completely beyond any
> expertise I ever had with these damn devices. I thought I understood
> the electrics and I thought I could diagnose most pressure related
> issues. But Iâ??m getting nowhere and itâ??s been going on for months and
> months����.
>
> Any ideas would be very welcome. Exceeding welcome.
>
> Simon
>
>
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Disclaimer: I'm not an O/D expert, having rebuilt exactly one with
reasonable success, but I can throw guesses around.<br>
<br>
I think <i>something</i> with the operating valve and its lifting
rod (bent?), but there's couple theoretical causes:<br>
<br>
- Too much wear on the cone clutch, causing it to stick in the brake
ring, but the guys at ODSpares would surely have noticed and
replaced/relined the clutch, no?<br>
<br>
- Something wrong with the operating pistons (one or both), not
allowing them to recede in their bores when pressure is relieved
(O-ring or steel rings?)<br>
<br>
I don't know enough about the intricacies of the internal
passageways, but I do know the accumulator regulates pressure pretty
simply: when the spring is compressed far enough a drain hole is
uncovered (not unlike how engine oil pressure is limited). If that
relief hole was somehow blocked pressure would increase until
something gave (like your gauge).<br>
<br>
An owner had a similar problem, reported on another forum. Someone
suggested the unidirectional clutch getting stuck, but I can't wrap
my head around that one (I think that would cause issues on overrun,
possibly damaging the O/D). <br>
<br>
So, the unit works fine on the test rig, but locks up first time you
engage it and stays there? May be a clue in there somewhere but, so
far, I'm coming up empty.<br>
<br>
BTW, did you use the newer accumulator type, with an 0-ring instead
of steel rings?<br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 6/18/2022 3:17 AM,
<a class="moz-txt-link-abbreviated"
href="mailto:simon.lachlan@alexarevel.plus.com";>simon.lachlan@alexarevel.plus.com</a>
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:000001d882fc$a2d7c9d0$e8875d70$@alexarevel.plus.com">
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<p class="MsoNormal">This saga started months ago and you may
remember the case and the various suggestions made at the
time. Iâ??ve been away and thus unable to get back to the
problemâ?¦.<o:p></o:p></p>
<p class="MsoNormal"><o:p>Â </o:p></p>
<p class="MsoNormal">The background was that the thing would go
into OD but not come out. And, after many
vicissitudesâ?¦removing box and OD in order to drive it up north
3(!) times, it is still playing up.<o:p></o:p></p>
<p class="MsoNormal"><o:p>Â </o:p></p>
<p class="MsoNormal">I shall try to give all the details and
background but that will entail my being as verbose as
usual.<o:p></o:p></p>
<ol style="margin-top:0cm" type="1" start="1">
<li class="MsoListParagraph"
style="margin-left:0cm;mso-list:l0 level1 lfo1">It is in a
MKII BT7 centre shift.<o:p></o:p></li>
<li class="MsoListParagraph"
style="margin-left:0cm;mso-list:l0 level1 lfo1">It has,
yesterday, new 30 wt non-detergent. Plenty of it.
Clean.<o:p></o:p></li>
<li class="MsoListParagraph"
style="margin-left:0cm;mso-list:l0 level1 lfo1">Its
electrics pass muster though I wish I could detect a fault
there so that I could fix itâ?¦. If the ignition is <i>on </i>and
the engine is <i>off</i>, when I put the stick in 4<sup>th</sup>
and engage OD I get a nice click and the little lever moves.
When I move the lever across to 1<sup>st</sup> and 2<sup>nd</sup>,
another click and slight movement on the little lever. When
I leave it in 4<sup>th</sup> but switch the OD <i>off, </i>it
stays engaged until I depress the accelerator a little and
then it drops out of OD. To my mind at least, this indicates
that the electrics are working. IS THAT PRESUMPTION CORRECT?
I tried it with a spare, rebuilt, relay but no dice.<o:p></o:p></li>
<li class="MsoListParagraph"
style="margin-left:0cm;mso-list:l0 level1 lfo1">There is
nothing in the little hole and the ball seats nicely. All
new parts in there.<o:p></o:p></li>
<li class="MsoListParagraph"
style="margin-left:0cm;mso-list:l0 level1 lfo1">The lever is
free to move when the ignition is off ie nothing in there is
slowing the leverâ??s freedom to move as pulled by the
solenoid.<o:p></o:p></li>
</ol>
<p class="MsoNormal"><o:p>Â </o:p></p>
<p class="MsoNormal">I have a (new) gauge and it goes up to 500+
psi when in 3<sup>rd</sup> or 4<sup>th</sup> and stays there
until I engage the OD. Pressure drops momentarily then returns
to 500+. All well and good. But it wonâ??t come outâ?¦.<o:p></o:p></p>
<p class="MsoNormal"><o:p>Â </o:p></p>
<p class="MsoNormal">My feeling, going somewhat against
received/informed advice, was that â??something was stuck inside
and not releasingâ??. This was borne out when, with the back
wheels off the ground, I was trying to find out what was going
wrong��the gauge was in and I was watching it. Into OD��.the
usual click plus a different sort of noise/clunk and a
distinct jerk. The gauge went off the scaleâ?¦.needle all the
way round and jammed on the reverse side of zero where it
remained; gauge destroyed. The gasket between the
solenoid/operating lever casing and the accumulator area
ruptured and oil started to come out. Fairly briskly. So that
was a complete disaster.<o:p></o:p></p>
<p class="MsoNormal"><o:p>Â </o:p></p>
<p class="MsoNormal">I rang up ODSpares, for the 400<sup>th</sup>
time, and Dave said that the accumulator â?? brand new, fitted
by them - must have jammed. He, very reasonably I thought,
said that if I brought the box and OD up <i>again(!)</i>,
heâ??d fit on a complete new unit. So, I did and he did. I
imagine that he fitted a casing with all new bits where
needed. He runs them on a rig for 8 hours before letting them
leave the shop��<o:p></o:p></p>
<p class="MsoNormal"><o:p>Â </o:p></p>
<p class="MsoNormal">Anyhow, I stuck the box etc back in â?? Iâ??m
getting quite good at that now â?? and had high hopes. But, no
good. The needle goes up to 500+ and stays there until I move
it in and out of OD by moving the stick left to right with the
ignition on and the engine off.<o:p></o:p></p>
<p class="MsoNormal"><o:p>Â </o:p></p>
<p class="MsoNormal">Logically, if logic applies to an OD, one
might suppose EITHER that there is a batch of dud accumulators
out there OR that there is some external factor that Iâ??ve
missed which has been lurking undetected all the while?!? BUT,
that would not have made the accumulator jam??<o:p></o:p></p>
<p class="MsoNormal"><o:p>Â </o:p></p>
<p class="MsoNormal">Is it possible that there is something
extraneous that could cause the electrics to play up only when
the engine is running?<o:p></o:p></p>
<p class="MsoNormal">Or, do ODs need a few miles on them before
they start working properly? Clutching at straws here!!<o:p></o:p></p>
<p class="MsoNormal"><o:p>Â </o:p></p>
<p class="MsoNormal">One last thing, Dave agreed that there was
still a pressure issue. He suggested drilling out the little
hole in the so-called â??valve â?? operatingâ?? (the rod under the
ball bearing). That was to allow the pressure to bleed off
faster. He sent me a new rod in case that didnâ??t work. Which
it didnâ??t! The hole was just a tiny fraction less than 1mm and
I drilled it out to 1.5mm. (Apparently, the factory used to
drill them out for competition vehiclesâ?¦)<o:p></o:p></p>
<p class="MsoNormal"><o:p>Â </o:p></p>
<p class="MsoNormal">Anyhow, Iâ??m stuck. As is the OD!. And Iâ??ve
gone completely beyond any expertise I ever had with these
damn devices. I thought I understood the electrics and I
thought I could diagnose most pressure related issues. But Iâ??m
getting nowhere and itâ??s been going on for months and
months����.<o:p></o:p></p>
<p class="MsoNormal"><o:p>Â </o:p></p>
<p class="MsoNormal">Any ideas would be very welcome. Exceeding
welcome.<o:p></o:p></p>
<p class="MsoNormal"><o:p>Â </o:p></p>
<p class="MsoNormal">Simon<o:p></o:p></p>
<p class="MsoNormal"><o:p>Â </o:p></p>
<p class="MsoNormal"><o:p>Â </o:p></p>
</div>
<br>
</blockquote>
<br>
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