[Healeys] Overdrive Conundrum
Bob Spidell
bspidell at comcast.net
Sat Oct 25 15:42:34 MDT 2025
Thanks Hank and Michael.
Here's the recommendations from the Bentley reprint of the shop manual
for the 6-cyl cars. It appears to me the recommendations changed with
the evolution of lubricant technology. Another lister mentioned, in a
PM, that he got the same symptoms when his solenoid/cross shaft enclose
filled with oil due to a failed O-ring.
After over 100K miles of running MT-90 in my gearbox the gears showed no
appreciable wear and no sediment in the bottom of the box. The layshaft,
however, was worn at the ends, so I replaced with a DWM 'uprated' shaft.
Getting the right thickness of thrust washer required, IIRC, stacking of
washers to get a gap in the enclosure, then doing a little math to
determine the required thickness of washer to close the gap. I couldn't
find a suitably sized washer--big enough for the mainshaft, but small
enough to fit--to get a measurement, so I went with the existing washer,
which was still in good shape. I think the way Magnus Karlson does it,
by getting the measurement then machining a washer to the correct
thickness is ideal.
Bob
On 10/25/2025 10:42 AM, Michael Salter wrote:
> Hank, I have never be able to find any recommendation from Laycock De
> Normanville which recommend any particular oil for one of their
> overdrive units.
> I wrote to the company (back in the day when one sent letters through
> the mail, many decades ago) and asked what lubricant they recommended
> and they replied that the lubricant was specified by the gearbox
> manufacturer.
> This 30 weight non-detergent thing is nothing more than an "old wives
> tale".
>
> M
> ------------------------------------------------------------------------
> *From:* Hank Leach <gradea1 at charter.net>
> *Sent:* Saturday, October 25, 2025 12:52:20 PM
> *To:* Michael Salter <michael.salter at gmail.com>; Bob Spidell
> <bspidell at comcast.net>; Healey team <healeys at autox.team.net>
> *Subject:* RE: Re: [Healeys] Overdrive Conundrum
> The required clearance for the sunwheel is .016-.020" If you swapped
> out the bearing there could be a difference from original. Moss and AH
> Spares sell the various sized steel washers depending on the reading
> you get. Typically, after many miles, that rear bronze washer is
> cracked or worn and should be replaced.
> The factory(when there was one) recommended to only use 30W Non
> Detergent oil as others tended to foam and cause pressure issues. Also
> to be sure it is properly topped up- #1-key reason to not work.
> Before you tear it down, why not just change the oil as recommended
> and see if there is a difference-easiest fix at this point. If not the
> problem then it needs to come out and repair. Hank
>
> --------------------
>
> From: "Bob Spidell via Healeys" <healeys at autox.team.net>
> Reply-To: "Bob Spidell" <bspidell at comcast.net>
> To: "Michael Salter" <michael.salter at gmail.com>, "Healeys"
> <healeys at autox.team.net>
> Sent: October 24, 2025 at 9:38 PM PDT
> Subject: Re: [Healeys] Overdrive Conundrum
> 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>
> <mailto:healeys-bounces at autox.team.net> on behalf of Bob Spidell
> via Healeys <healeys at autox.team.net> <mailto:healeys at autox.team.net>
> *Sent:* Friday, October 24, 2025 8:41:36 PM
> *To:* Healeys <healeys at autox.team.net> <mailto: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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