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Overdrive Stopped - Need help w/ trouble shooting...

Posted by AHark

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Re: Overdrive Stopped - Need help w/ trouble shooting... #21
thomaslea1 Tom Lea Central Illinois, USA 1968 MG MGB	Posted: May 07, 2012 02:04PM Registered: 5 years ago Posts: 647

In reply to # 2060876 by AHark I talked to the folks at Quantum, I'm going with a reconditioned OD unit when the have on in stock. If they don't get one in over the summer I'll wait till the end of the driving season and send mine to they for rework. The OD side clutch material sounds compromised.

I have no idea how you would determine that without taking it apart and looking. Just a guess, although an educated one, is still a guess. Unless you verify you have 400+ PSI and it still doesn't work, and there's nothing unusual in the screen, I wouldn't necessarily jump to conclusions. Mine was dropping out after 20 miles or so. A pressure gauge showed gradual loss of pressure from 417PSI downwards till it dropped out. I passed this by the usual experts and they blamed it on the clutch material. Disassembly (which isn't THAT difficult) showed that both piston seals ($.45 each) were bad.

If you need or want the OD overhaul part of the shop manual PM me with an email address.

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Re: Overdrive Stopped - Need help w/ trouble shooting... #22
RAY 67 TOURER Ray Marloff Fort Bragg, CA, USA 1967 MG MGB "My Girl"	Posted: May 07, 2012 02:05PM Registered: 3 years ago Posts: 5,952

Double check that solenoid. Mine did the same thing that yours is doing and it turned out to be a faulty solenoid that had a partial open circuit that would fail only fail once in a while. A new solenoid cured the problem. Your solenoid is over 35 years old and its insulation is probably starting to break down. A lot cheaper and easier to do than replacing the OD unit. RAY

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Re: Overdrive Stopped - Need help w/ trouble shooting... #23
pooch2 aussie 1968 MK 1 By the Beach, south coast NSW, Australia	Posted: May 07, 2012 04:43PM Registered: 4 years ago Posts: 4,174

In reply to # 2059896 by dickmoritz

In reply to # 2059876 by AHark Dick, I have power at the solinoid in appropriate gear, 3 and 4 only as it should be.

Andy,

Can you hear and feel the solenoid click in and out?

Dick

I thought you could only JUST hear an LH solenoid click in just the once , but it needed oil pressure to push it back?

May be wrong.

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Re: Overdrive Stopped - Need help w/ trouble shooting... #24
twhiteca Trevor Whitehouse Orleans, Ontario, Canada 1976 MG MGB "Abejita"	Posted: May 08, 2012 08:41AM Registered: 3 years ago Posts: 374

In for a penny - in for a pound.

I wouldn't be dumping the OD unit for an exchange too quickly. The OD units are very robust and will take some real neglect and abuse to kill. Having said that, they can be fiddly hydraulic devices that require the litte passages and galleries to be opened and closed properly for the unit to function as advertised.

That device that you haven't opened up and played with yet - the one that is protected by the access cap with the two holed cap screw - contains the high and low pressure relief valve. There are is a spring, a couple of o-rings and some shims in here to make sure that the valve acts properly to either recirc the oil in the OD oor pressurize the clutch pistons to engage the OD (the little eccentric-driven OD pump runs all the time when the transmission is turning) and if it was stuck or the oil screen or internals were gunked up ............

Much cheaper to follow the emminent Mr. Twist's multi-part video on opening up and cleaning the components and putting it back together than pulling the engine to change out the OD.

Edited 1 time(s). Last edit at 05/08/2012 08:46AM by twhiteca.

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Re: Overdrive Stopped - Need help w/ trouble shooting... #25
gooser Drake Myers Danville Va, USA	Posted: May 08, 2012 08:59AM Registered: 5 years ago Posts: 6,938

In reply to # 2061749 by twhiteca In for a penny - in for a pound.

I wouldn't be dumping the OD unit for an exchange too quickly. The OD units are very robust and will take some real neglect and abuse to kill. Having said that, they can be fiddly hydraulic devices that require the litte passages and galleries to be opened and closed properly for the unit to function as advertised.

That device that you haven't opened up and played with yet - the one that is protected by the access cap with the two holed cap screw - contains the high and low pressure relief valve. There are is a spring, a couple of o-rings and some shims in here to make sure that the valve acts properly to either recirc the oil in the OD oor pressurize the clutch pistons to engage the OD (the little eccentric-driven OD pump runs all the time when the transmission is turning) and if it was stuck or the oil screen or internals were gunked up ............

Much cheaper to follow the emminent Mr. Twist's multi-part video on opening up and cleaning the components and putting it back together than pulling the engine to change out the OD.

x2.

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