It is the oil pressure that actually makes the overdrive engage, and lack of
oil pressure causes disengagement because the overdrive sliding clutch moves
back under spring pressure when the oil pressure is removed. Theoretically,
you could add a pressure switch to sense the overdrive oil pressure and use
that to drive the warning light. But practically, I think it would be
difficult. The only place available to mount such a switch is to replace the
plug above the overdrive metering pin, so the switch would have to accommodate
that location.
The first modification I ever did to my BJ8 was to add an overdrive warning
switch. I didn't know anything about the overdrive, except that all the books
said never to reverse the car with overdrive engaged. I found myself
constantly doing that with the dash switch still selected to overdrive, but
wasn't aware that the gearshift switch was disengaging the overdrive as it was
supposed to do.
Anyway, I installed a red warning light above the ODRIVE/NORMAL switch to
remind me to turn that switch off before reversing the car. It has been doing
its job well for 33 years now. It illuminates when the dash switch is selected
O/DRIVE, so it doesn't tell me the overdrive is disengaged when turned off; but
I did discover a couple other useful functions of the switch:
The light stays on when turned off, until I press on the accelerator, then it
goes out. That tells me the overdrive throttle switch is adjusted properly.
It also helps to troubleshoot problems with the overdrive upstream of the
light. I once noticed that the overdrive suddenly wasn't engaging, and the
warning light was not on -- although the dash switch was in O/DRIVE. That told
me that the problem was electrical, not hydraulic. I found that the input
terminal of the dash switch had broken off and was still in the wire connector.
Steve Byers
HBJ8L/36666
BJ8 Registry
AHCA Delegate at Large
Havelock, NC
From: Healeys [mailto:healeys-bounces at autox.team.net] On Behalf Of Fred
Wescoe
Sent: Wednesday, June 28, 2017 12:46 PM
To: healeys
Subject: [Healeys] Overdrive
List,
Having just had the transmission and overdrive rebuilt, I am gun shy. I have
never had a problem previously with an overdrive disengaging when it is
switched off and I moved the shifter thru neutral and into 2nd. But,
apparently that was the case before I purchased the car and I did not realize
it. The overdrive appeared to work properly but in fact, it was not releasing
when it was turned off and that caused the problem. I am thinking about adding
a warning light that indicates the overdrive is still engaged even if the
switch is off and I'm trying to figure out how to accomplish this.
I believe that a light in the power line with solenoid simply means that the
solenoid is off but not that the overdrive is disengaged. The same is true
with all of the other switches.
What is the wisdom of the list on how best to do this. How can a warning light
be installed properly?
Thanks,
Fred
66 BJ8
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