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[Healeys] BN6 Overdrive

Subject: [Healeys] BN6 Overdrive
From: michaelsalter at gmail.com (Michael Salter)
Date: Sun, 8 Jan 2017 13:34:31 -0500
References: <FDF81D5C-7862-45F9-84FE-077FA7448EAC@gmail.com> <CAB3i7L+uDVmfsUpvgUDxL7=wGwdi0BFdD+w-y+4=C=HNDKhoHA@mail.gmail.com> <024d01d266a1$bbe74770$33b5d650$@rr.com> <323E6DFB61EB4CDFA59567584C4DA877@WINDOWST93OFP9>
Hi Roger,
I developed the "special tool"
<http://www.netbug.net/blogmichael/2015/01/24/laycock-de-normanville-overdrive-installation-tool/>
after becoming totally frustrated with the thin wire method that I could
never get to work reliably.
It is  a long time since I tackled the job that way but as I recall it is
necessary to remove the wire before the overdrive is fully mated to the
gearbox but do it too early and the pump plunger slips off the cam and too
late and the wire get jammed.
The "special tool" stays in place until the overdrive unit is tightened
right up.
The big problem with the "special tool" is where to keep between gearbox
jobs so I can find it next time!!!
Michael S
BN1 #174

On Sat, Jan 7, 2017 at 9:32 PM, Roger Grace <roggrace at telus.net> wrote:

> I currently have my BJ8 OD in a ?a thousand pieces? !
> Prior to stripping, I too built up a similar test rig but 240V variable
> speed with 3 ph motor as well. See pix.
>
> This rig was invaluable to help diagnose:
>     - low pressure that turned out to be a bad accumulator and piston
> rings; replacing with modern O ring style and new accumulator spring; used
> compressed air to extract the           accumulator.
>    -  confirm that front oil leak was GB front seal and not rear main ...
> phew!
>     - that brake ring flange was leaking oil; hopefully now fixed with
> Locktite 518; also leaks at adaptor flanges - new gaskets plus Hylomar.
>     - bad main clutch bearing; unit was noisy in direct 4th gear but much
> quieter in OD; this bearing only works in direct drive and not in OD; it
> was shot and interestingly                   could only be heard on test
> rig and not when in car with road and engine noise.
>
> Plan to run the transmission for several hours prior to reinstalling in
> car to get up to temp and check the leak enemy.
>
> Thinking ahead, was looking and making one of Michael S?s famous oil pump
> release tools; have done a few dry runs using the wire method and wonder
> why MS chose the wire tool over holding the spring with some thin wire as
> others have done ?
> rg
>
>
>
>
>
>
>
> *From:* Michael Salter
> *Sent:* Wednesday, January 4, 2017 8:47 AM
> *To:* BJ8Healeys
> *Cc:* Healey List
> *Subject:* Re: [Healeys] BN6 Overdrive
>
> Hi Steve,
> Best wishes for a Happy and Prosperous New Year.
> Yep those symptoms mostly make sense.
>
> *"The first time it would engage when cold, but not when hot.  The
> accumulator walls were severely gouged, probably from too much debris in
> the oil from not having been changed frequently enough before I got the
> car.  I found no other problems.  I concluded that the massive leakage
> prevented the accumulator piston from moving back far enough against the
> spring to direct the oil to the metering pin."*
> In this case unfortunately you don't mention the pre-repair test pressures
> but they would have been quite low, probably 300 odd cold and below 250
> hot, meaning that there was not enough pressure to move the clutch against
> the springs. I would imagine that as your drove and the oil heated up the
> unit would have started to slip and then dropped out of overdrive
> altogether.
>
>
> *The second time, the overdrive was slow to engage, felt like it was
> slipping, and would make a whirring noise as it tried to do so.  I put a
> gauge on the O/D and went for a drive.  I was reading 350 psi before the
> O/D switch was flipped, dropping to 100 psi at it tried to engage and back
> up to 350 - 365 psi after engagement.  I found a broken accumulator piston
> ring and a loose ring in the bottom of the accumulator bore.  After
> correcting that (and a broken thrust washer behind the planetaries), I read
> 450 psi before flipping the O/D switch and 250 psi as it engaged.  I
> neglected to record the recovery pressure.  This was done on a test rig and
> I did not repeat the test on the road since the O/D worked perfectly after
> reinstallation in the car.*
> In this case the pressure during engagement is a little low but that is,
> as you found, probably due to damage in the accumulator. I'm surprised to
> hear that it slipped with a 350 -360 engaged pressure but that may have had
> something to do with the broken thrust preventing full travel of the clutch
> member...not sure about that one..  I have experienced that whirring
> noise on some units as well I suspect it is the unidirectional clutch
> slipping.. I envy your test rig...I always intended to build one but I
> never got a round tuit...
> M
>
> On Wed, Jan 4, 2017 at 10:46 AM, BJ8Healeys <sbyers at ec.rr.com> wrote:
>
>> Mike, what I mentioned to Neil is that both times I have had problems
>> with my overdrive failing to engage, or engaging sluggishly, the problem
>> was the accumulator.  The first time it would engage when cold, but not
>> when hot.  The accumulator walls were severely gouged, probably from too
>> much debris in the oil from not having been changed frequently enough
>> before I got the car.  I found no other problems.  I concluded that the
>> massive leakage prevented the accumulator piston from moving back far
>> enough against the spring to direct the oil to the metering pin.
>>
>> The second time, the overdrive was slow to engage, felt like it was
>> slipping, and would make a whirring noise as it tried to do so.  I put a
>> gauge on the O/D and went for a drive.  I was reading 350 psi before the
>> O/D switch was flipped, dropping to 100 psi at it tried to engage and back
>> up to 350 - 365 psi after engagement.  I found a broken accumulator piston
>> ring and a loose ring in the bottom of the accumulator bore.  After
>> correcting that (and a broken thrust washer behind the planetaries), I read
>> 450 psi before flipping the O/D switch and 250 psi as it engaged.  I
>> neglected to record the recovery pressure.  This was done on a test rig and
>> I did not repeat the test on the road since the O/D worked perfectly after
>> reinstallation in the car.
>>
>>
>>
>> Steve Byers
>>
>> HBJ8L/36666
>>
>> BJ8 Registry
>>
>> AHCA Delegate at Large
>>
>> Havelock, NC
>>
>>
>>
>>
>>
>> *From:* Healeys [mailto:healeys-bounces at autox.team.net] *On Behalf Of 
>> *Michael
>> Salter
>> *Sent:* Wednesday, January 04, 2017 9:53 AM
>> *To:* Neil McDonald
>> *Cc:* Healey List
>> *Subject:* Re: [Healeys] BN6 Overdrive
>>
>>
>>
>> Hi again Neil,
>>
>> With all due respects to Steve I would not suspect the accumulator
>> because it is in the hydraulic circuit ahead of the operating valve.
>>
>> If the accumulator was leaking badly enough to prevent the overdrive from
>> engaging you would never see 390 p.s.i. if you are testing at the operating
>> valve plug with the ball and spring in position.
>>
>> Although the specified pressure for our units is 470 - 490 p.s.i. I have
>> never seen one achieve 490 p.s.i. and have found units that operated quite
>> satisfactorily with pressures as low as 300 p.s.i. hot.
>>
>> Someone suggested running the car on stands and manually lifting the
>> valve setting lever. That is how I test for correct operation BUT PLEASE be
>> ware of that driveshaft spinning next to your right hip. Getting yourself
>> tangled up in that will ruin your day.
>>
>> Michael S
>>
>> BN1 #174
>>
>>
>>
>> On Wed, Jan 4, 2017 at 6:05 AM, Neil McDonald <nmcd10 at gmail.com> wrote:
>>
>> Yesterday I wrote "I have concluded that the most likely cause of my
>> problems are low OD fluid levels and/or inadequate opening of the actuating
>> valve. Both I can  readily deal with."
>>
>>
>>
>> In off line discussions with Steve Byers I have added a third and ominous
>> possibility, a defective accumulator. The good hydraulic pressure already
>> confirmed only indicates that the pump is OK because testing was not done
>> while trying to engage the OD. My understanding is that OD engagement is
>> the accumulator's function and the pump's role is to pressurise the
>> accumulator for this task *before* OD engagement. A definitive test of
>> accumulator condition seems to be how well it holds pressure after the
>> engine is switched off!
>>
>> _____________________
>>
>> Neil McDonald
>>
>>
>>
>> Email: nmcd10 at gmail.com
>>
>>
>>
>>
>>
>>
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>>
>>
>
>
> --
> *If you can't fix it with a hammer, you've got an electrical problem.*
>
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-- 
*If you can't fix it with a hammer, you've got an electrical problem.*
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