[Healeys] overdrive problem

[Roger Grace]

I have found OD Spares in UK to always be very helpful and knowledgeable.

http://www.odspares.com/

They supply the O ring upgraded accumulator and piston set.  This piston is
slightly larger in diameter than the original.
As an aside, 2 years after upgrading  my BJ8 OD to their accumulator set,
the OD pressure still holds 480 psi after a week !!
rg

On Fri, Mar 26, 2021 at 7:49 AM Bob Spidell <bspidell at comcast.net> wrote:

> 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> 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> 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> on behalf of Bob
>>> Spidell <bspidell at comcast.net>
>>> *Sent:* Thursday, March 25, 2021 11:14 PM
>>> *To:* healeys at autox.team.net <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>
>>> <healeys-bounces at autox.team.net> on behalf of Kees Oudesluijs via
>>> Healeys <healeys at autox.team.net> <healeys at autox.team.net>
>>> *Sent:* Tuesday, March 23, 2021 7:37 AM
>>> *To:* healeys at autox.team.net <healeys at autox.team.net>
>>> <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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