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[Healeys] BN6 Overdrive

Subject: [Healeys] BN6 Overdrive
From: roggrace at telus.net (Roger Grace)
Date: Sat, 7 Jan 2017 18:32:52 -0800
References: <FDF81D5C-7862-45F9-84FE-077FA7448EAC@gmail.com> <CAB3i7L+uDVmfsUpvgUDxL7=wGwdi0BFdD+w-y+4=C=HNDKhoHA@mail.gmail.com> <024d01d266a1$bbe74770$33b5d650$@rr.com> OosOcqMoHaZXmOosPcOLnf
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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