[Healeys] Overdrive Conundrum

[john spaur]

That's very odd. When mu OD was acting up it would work properly when cold but would not work after itvwas hot. Replaced the accumulator pistons, housing and seals and that fixed the problem.

Seems your OD might have something binding after it heats up due to expansion but I would think that to be very odd and can't think what it could be.

________________________________
From: Healeys <healeys-bounces at autox.team.net> on behalf of Bob Spidell via Healeys <healeys at autox.team.net>
Sent: Friday, October 24, 2025 9:41:36 PM
To: Healeys <healeys at autox.team.net>
Subject: [Healeys] Overdrive Conundrum

Listers,

I have a problem with my BJ8's overdrive that defies conventional logic:
The O/D will not engage when the drivetrain is cold, but begins to
function more-or-less normally as the drivetrain gets fully heated-up
(15-20m on a warm day). I've checked the functioning of the electricals;
i.e. when not running I can a) disconnect the coil ground so as not to
fry the Pertonix Ignitor, b) place the gearbox in 3rd or 4th and c)
close either, or both, the dash switch and/or the switch on the shift
knob --they're wired in parallel so either one will engage the O/D, but
both need to be in off/open condition to disengage--and I can hear the
solenoid click firmly (this pretty much rules out the switches). I have
already replaced the scuttle relay to no effect (I have had them get
flaky). AFAIK, the throttle/'kickdown' switch only comes into play when
disengaging, and seems to work when the O/D does engage.

My thinking is, if the pump is failed or failing the O/D might work when
the fluid is cold but cease to function as the fluid heats up and thins
out (I've used Redline MT-90 successfully for over 100K miles or more;
it's equivalent to 50wt engine oil). But, the O/D not engaging when cold
(somewhat) refutes this theory. If the outlet check valve on the pump
was somehow boogered I would expect either a) cold function only, or b)
no function at all. Ditto the solenoid; I'd expect it to get flakey when
hot and it does 'click' reliably (when cold). I can imagine the lever on
the operating cam slipping, but wouldn't expect that to vary with
temperature (or to work at all, actually). Actuating shaft lift was
correctly set at rebuild. I do have a DWM 'uprated' accumulator
installed, and the O/D engages within 2 seconds when it functions.

Anyone had this condition, or have a theory as to why it behaves this
way? Next step would be to remove the console and confirm I have good
oil pressure (but if I do, then what?).

TIA,
Bob
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