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Re: 79B Overdrive Problems

To: "Richard A. Boris" <borisri@earthlink.net>
Subject: Re: 79B Overdrive Problems
From: Robert Allen <boballen@sky.net>
Date: Fri, 20 Jun 1997 08:53:32 -0500
Richard A. Boris wrote:
> 
> A fellow member of the MG Car Club-Long Island Center (MGCC-LIC) has a
> 79B roadster with a recently installed LH overdrive. The basic overdrive
> unit prior to installation had "o"ring replacements and basic pump
> check-out. The unit functioned for approx 1,000 miles and now will not
> engage in the overdrive position. Checked out the solenoid with normal
> car wiring and direct 12 volts, and the solenoid functioned. Also a
> replacement solenoid was tried with same results. The car was on a lift
> with rear wheels turing approx 25 MPH to see what happens when the
> electric power is applied, solenoid clicked in but the unit still failed
> to function. Anyone out there have any suggestions? and, can the LH unit
> be removed from the car on a lift without removal of the entire engine
> and gearbox to faciltate bench repairs?

Oil level proper? Running 'normal' oil without super slick additives?

The electrical solenoid is what usually goes. Having checked that, I
would look at the oil pump. The solenoid actually engages with oil
pressure. The electrical soloenoid mereley opens the valve. Somebody
nearer to a Bentley's manual can tell where the plug is to check oil
pressure.

I think the oil pressure can be checked and, if necessary, the oil pump
replaced, without removing the transmission. All of this assumes that
you have checked for electrical continuity all the way to the solenoid
-- there are a couple of switches that prevents the pump from working --
like not being in 3rd or 4th -- that need to be chased down. Sounds like
the on-the-rack test did this so, you need to meaurse the oil pressure.

Fortunately, my OD ain't broken yet so I ain't claimin' expertise here.

-- 
Bob Allen, Kansas City, '69CGT, '75TR6, '61Elva(?)
"A man of genuis makes no mistakes. His errors are volitional 
and are the portals of discovery" -- James Joyce in "Ulysses"

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