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Tips
Tips

overdrive

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Bill Toppin

Freshman Member
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Hi everyone
my overdrive on the BT7 works when it wants to. It seames to ease into od and just pop out when the toggle is on every thing seams to work when it wants. and I'm not sure on the throttle switch and its adjustment.
thanks for the ideas bill
 
You can do an advanced search to find all the threads on OD problems and operation that have already been written. There is a logical troubleshooting procedure that would help. I had similar symptoms to yours. When the OD oil was cold, it would ease into OD then pop out. I would have to pull over and start up again and as the oil warmed up it would work more reliably. However, I went through the whole procedure of cleaning out the accumulators, tapping the relief valve ball into its seat, and checking the operating lever adjustment. The throttle switch is only to allow the OD to turn off when the throttle is opened somewhat -- about 20% or so to avoid a harsh downshift. Norman Nock has a Tech Tips book (available from British Car Specialists) that has a lot more info.
 
Hi Bill, Try This remove the OD relay on the firewall. Carefully prise back the tangs. Hold the relay by it's base only and carefully clean the contacts and reassemble. May help.---Keoke
 
Just a note from personal experience. Tapping the ball bearing to get a better seal on the operating valve or the oil pump relief valve doesn't really work. In theory it is not a bad thing to do, unless you deform the ball bearing, causing it to be worse than before. From 2 overdrives I've torn down, and one I've built back up so that it works, I can tell you that the steel seat in the pressure relief valve is more likely to be pitted than anything else,and the ball bearings do wear so that they can never be made good. A medium weight tap probably won't hurt, but in my opinion it probably won't fix a problem either. Lapping the seat and replacing the ball can, and did for me, make a world of difference. With things disassembled and using magnifying glasses I could see that no amount of tapping the ball bearings into their seats would have done anything in my case.
 
I had the same sense of disbelief that the tapping would do anything, but it was one of the things I did (very lightly), after which the OD is working great. I think cleaning the accumulator of sludge was the biggest contributor. At one point I lost all oil pressure (after removing the transmission to replace the clutch) and drained the oil twice and that was when I took apart the accumulator and the ball bearing etc. and cleaned it up and regained pressure.
 
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