[Healeys] Overdrive pressure not releasing.
Bob Spidell
bspidell at comcast.net
Mon Apr 18 09:24:29 MDT 2022
Wouldn't opening up an O/D with 500psi be kind of messy?
On 4/18/2022 8:03 AM, Roger Grace wrote:
> To confirm Michae's analysis, consider:
> remove ball, spring and plunger
> remove the valve push rod and inspect - I use a piece of steel wire
> of appropriate thickness to pry out.
> replace the push rod - it should go in smoothly
> insert the wire again and push down gently; with your other hand
> operate the cam and you should feel the operating rod move up and down
> on the cam.
> if not MS is correct and the pin/peg has failed....
> of course it could also be the cotter pin that goes through the
> setting lever - but less likely IMO
> BTW I have found that my OD (O rings) holds 400 psi for several days.
> rg
>
>
>
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>
> On Sun, Apr 17, 2022 at 3:21 PM Simon Lachlan via Healeys
> <healeys at autox.team.net> wrote:
>
> That’s the one I’ve got. I did get an increase in pressure. No
> question about that.
>
> I talked to Dave at OD Spares with regard to the various
> accumulators out there at the moment. I don’t recall exactly but
> he supplies all of them to his customers and, I think, to the
> suppliers.
>
> Simon
>
> *From:*Healeys <healeys-bounces at autox.team.net> *On Behalf Of *Bob
> Spidell
> *Sent:* 17 April 2022 23:06
> *To:* Michael Salter <michaelsalter at gmail.com>
> *Cc:* healeys at autox.team.net
> *Subject:* Re: [Healeys] Overdrive pressure not releasing.
>
> AH Spares has an accumulator and piston which uses an O-ring. It
> appears the pressure relief hole is chamfered:
>
> https://www.ahspares.co.uk/austin-healey/performance-parts/gearbox-overdrive/o-ring-conversion-accumulator-piston.aspx
>
> On 4/17/2022 12:03 PM, Michael Salter wrote:
>
> Actually Bob I've never used an "O" ringed accumulator.
>
> I spent a little time many years back looking into using "O"
> rings on the accumulator but couldn't resolve the issue of the
> ring being chaffed when passing over the radial drillings in
> the accumulator body.
>
> Does anyone know how that has been solved?
>
> M
>
> On Sun., Apr. 17, 2022, 2:49 p.m. Bob Spidell,
> <bspidell at comcast.net> wrote:
>
> Michael,
>
> Sounds like you're implying the O-ringed accumulator is
> superior to the metal ring (OEM) type? Wish I'd known
> about it when I rebuilt my O/D (I bought the DWM 'uprated'
> accumulator).
>
> I'll throw out another, very unlikely, potential cause:
> the cone clutch could be stuck together. I've heard of
> this happening, but have never experienced it my self--nor
> has anyone I know--but it's theoretically possible (esp.
> if the clutch is excessively worn). Could this be the
> reason the manual is adamant about replacing the 8 strong
> springs, of two lengths, that oppose the operating pistons
> on overhaul, regardless if they still seem robust?
>
> On 4/17/2022 9:31 AM, Michael Salter via Healeys wrote:
>
> Simon,
>
> Based upon your synopsis I conclude that the operating
> valve is NOT opening when either the solenoid lever or
> the setting lever is being moved to the position where
> the operating valve ball would normally be lifted off
> its seat.
>
> This conclusion is based upon your discovery that the
> pressure in the accumulator, as indicated on the
> gauge, does not leak away overnight.
>
> There is a small clearance between the operating valve
> push rod and the overdrive housing. If the operating
> valve ball was indeed lifted off its seat all the oil
> in the accumulator would, over time, leak past the
> operating rod thus discharge the accumulator.
>
> This process would indeed take some time but would
> certainly completely relieve most, if not all the
> residual accumulator pressure overnight.
>
> If however the operating valve ball is still in
> contact with its seat (i.e. not being lifted) the oil
> pressure would not reach the small clearance between
> the valve push rod and the housing and, other than
> past the accumulator rings there is nowhere for that
> pressure to be relieved.
>
> I would presume that Overdrive Spares installed an
> accumulator with an "O" ring rather than the original
> cast iron rings. If the original type accumulator
> piston was still fitted, oil would seep past the cast
> iron rings to relieve the pressure, albeit very
> slowly, and again the accumulator pressure would be
> discharged overnight..
>
> The cam on the operating shaft, the one which lifts
> the operating valve push rod and thus the operating
> valve ball, is locked to the shaft with a small taper
> pin. I would guess that the taper pin has either
> fallen out or sheared.
>
> Bad news is that this pin cannot be accessed without
> removing and disassembling the overdrive.
>
> M
>
> On Sat, Apr 16, 2022 at 1:19 PM Simon Lachlan via
> Healeys <healeys at autox.team.net> wrote:
>
> My OD is driving me mad and I definitely need some
> inspired advice. A bit of background first. I’ll
> try to lay out all the facts in a logical
> sequence. (I’m increasingly reluctant to link ODs
> with logic!)
>
> 1. I’d say that the OD has done +/- 15k miles
> since a total rebuild by Overdrive Spares here
> in UK.
> 2. The OD had issues before Christmas (21) and
> was sorted out by OD Spares. The accumulator
> was uprated and pressure issues sorted.
> 3. OD functioned 100% on the few times I’d been
> able to take it out since then until..
> 4. One day, the OD stopped functioning.
> 5. I checked the electrics. All fine there so I
> delved a bit deeper.
> 6. It had fried its solenoid which I replaced. But…
> 7. That did not fix the problem so…
> 8. I decided that the operating valve’s
> adjustment might be off so..
> 9. I bought a dial gauge and hoped to sort it out
> precisely rather than by “feel”, which I lack
> in this area.
> 10. Prior to using the gauge I decided to see if
> the OD was functioning at all so I raised the
> car on stands and fitted my pressure gauge.
> 11. I get a reading of 500psi rising a bit when I
> rev the engine but I’d suppose that would drop
> when the oil warms up.
> 12. BUT, and this is where things go
> pear-shaped…moving the little lever on the RHS
> up and down does not engage/disengage OD.
> There is no change on the gauge to show OD
> engaging or disengaging.
> 13. AND, the gauge stays at 500psi even when the
> engine is off. Moving the lever 20 times has
> zero effect. Stayed at 500 overnight!
> 14. Of course, I checked for dirt in the operating
> valve area. None.
> 15. Likewise, the tiny hole in the “valve –
> operating” (the spindle thing which the ball
> sits on)….that’s clear. And surely, the
> pressure would diminish overnight if something
> in that area was partially obstructed?
> 16. When I remove the pressure valve, there’s a
> small spillage – no more than you’d expect –
> but repeating the pressure gauge process only
> returns the same results.
> 17. I see in the bible according to Norman Nock
> that “Holding this lever with your thumb and
> index finger, you should be able to push the
> lever down lightly about ⅜” until you feel a
> slight spring pressure resistance. The lever
> should go down another ¼” after encountering
> the resistance……” ie there’s about ⅝” movement
> up & down in that lever. Well, my lever does
> move and does lift the ball, but there’s not
> ⅝” movement there. Could that be the problem
> area???
> 18. Almost finished…keep reading!
>
> So, I’m stumped. Every time I learn something new
> about the OD, it has a new trick to baffle me.
>
> I’ve no 100% sure way of telling whether it’s gone
> into OD and stuck there or whether it’s simply
> not going into OD at all.
>
> I’ve done a lot of reading through my books and
> collection of advice from the various gurus and
> found reference to ODs being stuck but those
> seemed to be to do with “weak springs” which,
> particularly after a long lay-off, wouldn’t
> disengage. The cure for this being a good smack on
> the steel plate sandwiched in the OD from below.
> Well, that seems to be a stuck mechanism issue
> whereas I’m facing a hydraulic conundrum. Or am I?
>
> There is what is usually referred to as the
> “pressure relief valve” adjacent to the
> accumulator. The name suggested that pressure
> might be stuck in that area….but surely not overnight?
>
> Any ideas? I am particularly reluctant to take the
> gearbox and OD out. You’ll recall the ridiculous
> business of the defective clutch kit? Well, I
> forget whether we had the box in and out 3 times
> or 4. I’d hoped not to do it again so soon or ever
> for that matter.
>
> I’m hoping for a miracle of course but some sound
> advice would be a godsend…………
>
> Thanks,
>
> Simon
>
>
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