[Healeys] overdrive problem

[Bob Spidell]

OK, I did the hard work (2 clicks) and dug up the source:

https://www.ahspares.co.uk/austin-healey/performance-parts/gearbox-overdrive/o-ring-conversion-accumulator-piston.aspx

They claim the housing is modified as well, maybe with bevels on the 
pressure relief ports?

On 3/26/2021 7:34 AM, Michael Salter wrote:
> Bob, I looked into installing "O" rings into an accumulator many years 
> ago but couldn't figure out how to get around the problem presented by 
> the fact that the accumulator relieves pressure by allowing the cast 
> iron rings to pass over radial holes in the body.
> When I tried them the "O" rings were forced into those pressure relief 
> holes and tiny pieces were sliced off at each hole location!!
> How do the accumulators with "O" rings address that issue?
>
> M
>
> On Fri, Mar 26, 2021 at 10:26 AM Bob Spidell <bspidell at comcast.net 
> <mailto:bspidell at comcast.net>> wrote:
>
>     Maybe of interest to some: AFAIK, all O/D accumulators came with
>     metal rings, which likely cause or at least contribute to scoring.
>     One of the Brit suppliers--probably AHS but I'm not sure--has an
>     accumulator setup that uses an O-ring(s) instead of metal rings,
>     which should prevent scoring. I rebuilt my O/D a couple years
>     back, and if I'd known of the O-ring type I would have installed
>     it. Earlier O/Ds used metal rings in the actuator pistons, but
>     later ones had O-rings, and it's logical to conclude LdeN went to
>     O-rings there because of excessive scoring of the cases (or,
>     possibly, because they were cheaper).
>
>     On 3/26/2021 6:03 AM, Michael Salter via Healeys wrote:
>>     Time this question was put to bed.
>>     1. The throttle switch is not supposed to disengage the overdrive
>>     if the dash switch is in the "OVERDRIVE" position. If it does the
>>     system is wired incorrectly. (BN1s are a little different)
>>     2. Overdrives which slip out, slip, or won't engage WHEN HOT but
>>     do work when cold are invariably suffering from low oil pressure
>>     which is almost always caused by accumulator issues.  The "O"
>>     rings on the outside of the accumulator sleeve can be a problem
>>     but in my experience scoring of the accumulator bore and damage
>>     to the rings and piston are a more common cause.
>>     3. Overdrives and gearboxes in Healeys are meant to be lubricated
>>     with engine oil. Decades ago I  wrote to Laycock DeNormanville,
>>     back when letters went in envelopes with stamps, and received a
>>     response from their engineering department indicating clearly
>>     that the oil specified for their products was specified by the
>>     gearbox manufacturer and whatever they specified was acceptable
>>     for the overdrive.
>>     M
>>
>>     On Fri., Mar. 26, 2021, 2:13 a.m. WILLIAM B LAWRENCE via Healeys,
>>     <healeys at autox.team.net <mailto:healeys at autox.team.net>> wrote:
>>
>>         The symptoms I’ve seen and experienced are that the OD will
>>         engage and function until the oil temp comes up and the
>>         viscosity drops off and will then fail. I suppose it depends
>>         on the degree of degradation of the o-rings.
>>         ------------------------------------------------------------------------
>>         *From:* Healeys <healeys-bounces at autox.team.net
>>         <mailto:healeys-bounces at autox.team.net>> on behalf of Bob
>>         Spidell <bspidell at comcast.net <mailto:bspidell at comcast.net>>
>>         *Sent:* Thursday, March 25, 2021 11:14 PM
>>         *To:* healeys at autox.team.net <mailto:healeys at autox.team.net>
>>         <healeys at autox.team.net <mailto:healeys at autox.team.net>>
>>         *Subject:* Re: [Healeys] overdrive problem
>>         Sure, but wouldn't faulty O-rings prevent the OD from
>>         engaging in the first place? Just guessing, but wouldn't a
>>         deficient pump cause same symptoms?
>>
>>
>>         On 3/25/2021 4:07 PM, WILLIAM B LAWRENCE via Healeys wrote:
>>>         Sorry, but the Laycock deNormanville overdrive is not
>>>         supposed to kick down automatically. The most common fault
>>>         that causes the OD to drop out is faulty o-rings on the
>>>         accumulator sleeve. This won’t allow the OD to build full
>>>         operating pressure.
>>>
>>>         Bill Lawrence
>>>         BN1 #554
>>>         ------------------------------------------------------------------------
>>>         *From:* Healeys <healeys-bounces at autox.team.net>
>>>         <mailto:healeys-bounces at autox.team.net> on behalf of Kees
>>>         Oudesluijs via Healeys <healeys at autox.team.net>
>>>         <mailto:healeys at autox.team.net>
>>>         *Sent:* Tuesday, March 23, 2021 7:37 AM
>>>         *To:* healeys at autox.team.net <mailto:healeys at autox.team.net>
>>>         <healeys at autox.team.net> <mailto:healeys at autox.team.net>
>>>         *Subject:* Re: [Healeys] overdrive problem
>>>         That is the way it should be when accelerating hard, Kick down!!
>>>
>>>         Kees Oudesluijs
>>>
>>>
>>>         Op 23-3-2021 om 01:06 schreef healeymanjim via Healeys:
>>>         > friends BT7 had o/d quit.  solenoid was bad so replaced
>>>         it.  now it will go into o/d but pop out when
>>>         accelerating.   any
>>>         > ideas what the cause is and the fix?
>>
>

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