[Healeys] Overdrive Conundrum

Fri Oct 24 22:22:34 MDT 2025

Hi Michael,

I rebuilt the gearbox and O/D probably about 7-8 years or so ago. I've 
probably put close to 10K miles on it since, but not too many since I 
moved to the Central Valley. For the last few years it's been mostly 
short and day trips every month or two so, it's been mostly sedentary. A 
few months ago I took it out for a spin and noticed the O/D wouldn't 
engage at first but would start working normally after maybe 20 minutes 
of driving. In subsequent runs it's more not engaging, until a few days 
ago I'd decided I would likely have to pull the gearbox and O/D, but had 
to pull it out to get it off the QuickJack underneath it and, to my 
surprise it started to work OK again after 15-20 miles.

I rebuilt the O/D myself, and I think I did OK except I may not have 
gotten the planetary gears depth exactly right; I didn't have a 
selection of thrust washers to try so I just put the existing one back 
in. The only thing I changed out was the thrust ring bearing, which 
might have been a different width. The unit did have a very slight 
vibration, barely noticeable through the floorboards but otherwise 
operated perfectly. Now, when it works, it seems fine. When I rebuilt 
the gearbox the rearmost thrust washer was whacked (see pic), but of 
course I replaced it (how that could happen and why the O/D worked is 
another mystery). I couldn't get the GB and O/D to mate up so I took 
them to BCS where David Nock got them together and set the operating 
shaft lift. Besides trying a new relay at Tom Monaco's suggestion I 
haven't done anything else to it.

Only thing I can guess is maybe the lever that the solenoid lifts to 
turn the valve operating cam maybe slips sometimes and not others.

Bob

On 10/24/2025 8:00 PM, Michael Salter wrote:
> That does defy logic Bob.
> Can you give a little history, has it always been this way or did you 
> change something? Did the problem develop slowly or over time?
> Anything else that may be relevant?
>
> M
>
>
> ------------------------------------------------------------------------
> *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 8:41:36 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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