[Healeys] overdrive problem

Fri Mar 26 08:48:07 MDT 2021

Enlarging the photo clearly shows beveling on the relief ports.

On 3/26/2021 7:39 AM, Bob Spidell wrote:
> 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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