Overdrive problems Again!

[BEEJAY7]

Hope someone can help........

I've been having problems with my overdrive, which I thought I had repaired with the assistance of a hammer!....This turned out to be a temporary fix only.

The overdrive on my 62' BJ7 works great from cold and for about the first 15- 20 miles of a run and then for no apparent reason either drops out (if engaged) or refuses to engage (if in direct top).


If I stop the car for 30 mins, all is OK again.

The car runs at normal operating temprature, (160-180, and shows no sign of overheating, (I have checked the bulb on the temp Sender and it is operating correctly.

All wiring appears OK and the "kick down" switch is working correctly.

The problem first occured when driving hard on a Dual Carrigeway road, (sort of little Freeway!).

If anyone has any idea's they would be appreciated..

Cheers

Alan

 

[Steve]

I think that there is a solenoid which actually engages or disengages the overdrive. If this is faulty it could cause this problem. You may be able to get away with cleaning it, if not, a replacement should be available without too much trouble.

 

[John Morrison]

Hello BEEJAY7:
I assume that you've checked the easy stuff, like insuring that you have the correct oil in the gearbox, and that it is full.

It sounds as though the problem is temperature dependent.
If the "drop out" is abrupt, I would suspect the operating solenoid which is mounted on the side of the overdrive unit, or less likely the gearbox switch which keeps the OD from engaging in 1/2/R gears. It could also be the OD relay, but I doubt it.
If the dropout is gradual (i.e. slipping under acceleration, and finally disengaging), I'd suspect internal leakage in the overdrive, caused by "o" rings on the operating pistons, or in the accumulator. A Less likely cause is the hydraulic pump or the foot valve.

In order to determine whether the problem is electrical or mechanical, I'd "hotwire" the OD solenoid by running a direct line from the OD dashboard switch to the OD solenoid. There should be a "bullet" connector very close to the solenoid that you can plug in to. This will by-pass the OD relay, the throttle switch, and the gearbox switch. Go for a ride and see what happens. (make sure the od is OFF before engaging 1st 2nd, or Reverse)
If the problem doesn't re-occur, then it is one of the by-passed components.

If it still drops out, it's either the solenoid or an internal leak. Do this:
Remove the gearbox cover and fabricate a sheet metal shield to cover the U-joint. Either go for a ride (with a passenger to help observe), or put your healey up on blocks to simulate driving. The operating lever(below the solenoid) will move between 1/4 and 1/2 inch when it engages or disengages. If, when the "drop-out" occurs, the operating lever drops, then the problem is the solenoid. If the drop-out occurs, then it is an internal problem in the overdrive unit, i.e. "o" rings, or pump.

Hope this helps

Regards,
JOHN

 

[BEEJAY7]

Thanks John and Steve.

I found the problem this weekend. The main power feed to the solonoid was cracked internally, so a replacement cable solved the problem. Only took me three hours to find the fault!!..

Cheers

Alan