[Healeys] Overdrive

Wed Jun 28 21:36:18 MDT 2017

I've heard of the overdrive failing to disengage due to the clutch lining sticking to the brake ring. I'm not sure why that would happen other than excessive wear on one or the other or possibly the use of the wrong lubricant. the solution as I recall was to tap the brake ring with a hammer from under the car. The danger is that you would not Know it had not disengaged and try to drive in reverse. If I were afraid this might be happening to my car I would engage the overdrive while it was running and then stop the engine and, placing it in reverse gear, try gently rocking the car backwards. If there's no resistance from the drivetrain you are golden. otherwise you need to pull the OD and find out what is causing the problem. The best protection is to come out of OD while you are still moving in a forward gear and to be constantly aware that the OD is actually disengaging as it should.

Bill Lawrence

BN1 #554

From: Healeys <healeys-bounces at autox.team.net> on behalf of BJ8Healeys <sbyers at ec.rr.com>
Sent: Wednesday, June 28, 2017 11:42:20 PM
To: 'healeys'
Subject: Re: [Healeys] Overdrive

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
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


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?


66 BJ8

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