[Healeys] Overdrive Conundrum
Bob Spidell
bspidell at comcast.net
Sun Oct 26 22:51:32 MDT 2025
When I first started using MT-90 in my BJ8 I changed out the fluid at
15K miles (Norman Nock's recommended interval). I drained into a
perfectly clean pan, took the fluid out into the bright sunlight and
observed it had what I called 'shake;' shiny brass particles floating in
the amber fluid. It was quite pretty, like a super fine metal flake
paint, but the brass particles were so fine you could rub the oil
between your fingers and not feel a thing. In short, they were too small
to plug any of the passages in an O/D. Anyone who's rebuilt a
Healey/Mowog gearbox knows the brass shift forks are a consumable item
(and easily restored). Note quality greases are merely oil thickened
with a very finely ground, soft metal; e.g. lithium, molybdenum
('moly'). The cheap stuff usually uses diatomaceous earth.
The only (supposed) reason I've ever heard for using non-detergent oil
in a gearbox is to let the brass, and other contaminants settle into a
sludge at the bottom of the gearbox, so it doesn't circulate through the
O/D and possibly plug one of the small passages (anybody heard a
different 'logic?). But, the job of a detergent is to clean
contaminants--soot, etc.--from the combustion chambers and, in
particular, ring lands. It's the job of ashless dispersants to keep
particulates suspended in the oil, so as NOT to contribute to sludge
buildup, so spec'ing an AD oil/might/ make some sense (but what happens
when a chunk of sludge starts migrating around the gearbox; blood clot
anybody?). Note I read somewhere, but can't provide a source, that ZDDP
was first added to oil as a detergent, before its anti-wear properties
were known (rule of thumb: if something has 'phosphate' in its chemical
name it likely has detergent properties).
Some differences are pointed out here:
https://www.cnlubricantadditive.com/info/difference-between-dispersants-and-dertergents-91273973.html
Our mechanics always insisted we use AD/mineral oil for engine break-in
in our aircraft engines--no mention of 'non-detergent'--because
air-cooled aircraft engine cylinders are notoriously tricky to break-in
properly due to the loose clearances and (sometimes) chrome cylinder
coatings. AD oil was thought to help 'wear in' the rings (when the
break-in failed I've heard of owners putting Bon Ami in the cylinders).
AFAIK, most modern, off-the-shelf oils contain both dispersants and
detergents.
Their is a cadre of owners and mechanics that seem to think our cars
should only get the oils, etc. that were available when the cars were
first manufactured, ignoring the tremendous advances in lubricant
science ('tribology') in the last 70 years or so. I've attached the
recommended lubricant chart from the Bentley reprint for the 6-cyl cars,
showing how the recommendations 'evolved' as multi-vis oils became
available--early 60s, I think--and no mention of 'non-detergent.' I
don't see any particular advantage to using a multi-vis in a gearbox; I
suspect BMC simply wanted to limit the types of oil the mechanics had to
stock, and engine oil was good enough (I suppose a mult-vis might shift
a little better when cold, but I ran Castrol 20W-50 for a few years and
didn't notice any benefit; admittedly in a temperate climate).
When I overhauled my gearbox/OD at 205K miles there was only slight wear
on the leading edge of 2nd gear. The O/D accumulator showed typical
scoring, and I replaced one bearing that probably didn't need to be
replaced, but otherwise all the moving parts were pristine, the O/D
screen had just a few small particles and the cone clutch had
significant material left and I put it back in (they appear to be of
limited supply; DWM relines them). Not a spec of 'sludge' anywhere.
Redline MTL has equivalent viscosity to 30WT motor oil; MT-90 is
equivalent to 50WT. Yes, synthetic oils may leak a little more, but I
ran my old Lincoln LS with a Jaguar engine on 5W-30 full synthetic and
it didn't leak a drop. Go figure.
Bob
On 10/26/2025 5:12 PM, Roger Grace wrote:
> OK have resisted commenting on this controversial topic for a few years.
>
> Long story about OD oil to add to the oil confusion.
> I have made up a VS test rig for running a GB plus OD at different speeds.
> Very useful for functional and OD oil leak hunting
> Several years ago, after a rebuild I filled with Castrol 30WT ND oil -
> no issues OD engaged fine.
> On same GB after a few days after running for 2-3 mins from cold,
> drained the oil (to fix a leak) and noted very significant foaming
> with the classic fish eye bubbles.
> The GB oil seemed foamier than the OD
> Repeated this test and same story.
> Also 2 others observed the same foaming, and on one was so bad that OD
> would not engage.
> We all changed to MT90.
>
> Out of curiosity wrote to Castrol about this.
> See reply below.
>
> /"Thank you for contacting Castrol North
> America./
>
> /Castrol does not recommend our Non-Detergent for manual transmission
> applications, and we believe the foaming was likely caused
> by some type of contamination, perhaps water in the
> transmission./
>
> /Unfortunately Castrol does not offer a manual transmission
> fluid product in Canada or the US./
>
> /Castrol Consumer Relations"/
>
> There certainly was no moisture in the tranny.
>
> Not sure if foaming is a bad thing ? What is disturbing is that if I
> hadn't drained the oil I would have been none the wiser about the
> foaming. Maybe this is normal. I suspect that it disappears after some
> use and only evident soon after starting ?
>
> To hopefully reduce pesky weeping leaks now use regular engine oil
> 20-50 VR1
>
> rg
>
>
>
>
>
>
> On Sun, Oct 26, 2025 at 3:56 PM Mike Sinclair via Healeys
> <healeys at autox.team.net> wrote:
>
> Interesting, the comment on Redline. I have used it in my ancient
> Honda and the gearbox noises went away.
>
> Mike
>
> On 10/26/25 5:53 AM, Simon Lachlan via Healeys wrote:
>>
>> Just to keep the pot boiling……………when I was up at OD Spares
>> talking to Dave Twigger, I asked him which oil to use in my OD.
>> “20-50”, he replied very firmly. Over here, UK, OD Spares is
>> somewhat regarded in the same light as AH Spares. Dave’s
>> father-in-law worked for Laycock and, when they stopped
>> manufacturing ODs, he bought all the remaining stock and started
>> up on his own. (Or something similar…..Dave did tell me but ages
>> ago). Anyhow, I’d say that Dave and son are our leading OD
>> experts. His workshop is surprisingly small and slightly scruffy
>> but is stuffed with all the right spares, test beds and spares.
>> Michael, I recall you saying the same.
>>
>> I have to say that I use 30 or 40 non-detergent, which he says is
>> fine. After fixing my OD, he put my 30 wt back in perfectly
>> happily. He was absolutely against Redline and similar products…..
>>
>> Simon
>>
>> *From:*Healeys <healeys-bounces at autox.team.net>
>> <mailto:healeys-bounces at autox.team.net> *On Behalf Of *Michael Salter
>> *Sent:* 25 October 2025 18:42
>> *To:* gradea1 at charter.net; Bob Spidell <bspidell at comcast.net>
>> <mailto:bspidell at comcast.net>; Healey team
>> <healeys at autox.team.net> <mailto:healeys at autox.team.net>
>> *Subject:* Re: [Healeys] Overdrive Conundrum
>>
>> 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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