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MG MGF Technical - O/D - intermittent when disengaged on deceleration

I own a 1969 MGBGT with a LH overdrive. The overdrive engages fines and operates well. My question is that sometimes (not always) when I disengage the overdrive while decelerating (ie exiting a freeway) it feels as if the overdrive engages and disengages several times. It really only seems to last during the deceleration but can happen in either 3rd or 4th gear. The oil level is good in the transmission. I am guessing that it has something to do either with either: a. the OD oil pump, b. loose inhibitor switch, c. wiring. Any words of wisdom out there?
Jonathan Seal

If you ask this question in the MGB Technical forum you might get a better response Jonathan. The MGF does not have a OD, just 5 normal gears. Fifth is an overdrive ratio.
Neil Courtney

Jonathan,

I used to have an MGB with a similar problem.

It was evetually tranced to the inhibitor switch which is operated by the gear lever mechanism while in 3rd and 4th gear.

The plunger had worn down and was fixed by the addition of a couple of spacing washers to "extend" the plunger out a bit.

To prove this, put some tension on the gear lever when you expect the fault to manifest itself.

Good luck!

Sam
Sam Murray

The symptoms are also very simliar to those of another problem I have encountered more than once, and have described it here:

http://www.mgparts.co.nz/overdrives.html
(go down to the bottom of the page, overdrive pumping)

Although not noted there, it occurs mainly on overrrun because of the effect of the unidirectional clutch.

I'm not sure what triggers it, possibly a swollen seal, causing it to stick, so replacing that seal might sort it. However one cure is very simple: Just add another gasket under the square plate which holds the solenoid in (make sure it has a hole in the middle). With a bit of extra clearance between the plunger and this cover, the plunger can move back properly and the problem goes away.

Paul

Paul Walbran

This thread was discussed between 08/05/2006 and 09/05/2006

MG MGF Technical index

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