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MG MGB Technical - Overdrive Issues

Right, any suggestions that will save me from an engine removal will be most welcome.

I recently (2 weeks ago) changed the oil in the gearbox of my 1978 mgb roadster as part of a general service ready for MOT and summer motoring. As far as I can remember all I did to the gearbox was change the oil, nothing else.

The problem: lack of overdrive. Well, virtually anyway. First thing in the morning the o/d will operate if a little sluggishly for the first few miles and then it will give up operation. Also, the o/d will slip in and out of operation for thenext few miles with pressure on the throttle (press and the o/d slips out, release and the o/d engages). And then nothing.

I'm pretty sure the electrics are working because of the little operation first thing. The oil level was overfilled initially because the hosepipe I was using stopped any overflow (blocking the filler hole) and I forgot to let it settle before replacing the filler plug. I ran it for about 20 miles before remembering and have since let out the excess.

So far I've been suggested to remove the solenoid and clean, and to clean the filter and magnets next to it. Both of which require draining the gearbox. Are there any other suggestions? If these two don't work then I suppose I'm looking at a replacement o/d. I can't (won't) afford the costs of putting the car in a garage to get it looked at.

Rick
Rick Haynes

Rick,

Check the oil level!

Your symptoms are classic for a low oil level in the gearbox.
Chris at Octarine Services

OK, didn't see that one coming. Too little oil in the gearbox?

I filled the gearbox with Valvoline 20W/50 through a filter via a hosepipe from the engine bay. After removing the hosepipe, the gearbox drained some (100ml or so) oil into a tray. I then refitted the filler plug. I'll check again, but I'm sure the oil level is up to the filler hole. Chris, if I get nowhere I may give you a call for some more advice (in office hours naturally).

Anything else.

Rick
Rick Haynes

Rick,

It's also a good idea to clean the filter on the overdrive unit. This is the flat plate underneath(yes easy to get to!) Becarefull not to over tighten the 6 bolts that hold it in place as they shear very easily.
The filter itself is just a metal gauze. Oh and the gearbox needs to be empty!!

TJ
T J Nicolson

Did you recheck the level after running it?
Paul Hunt

This thread was discussed on 23/03/2004

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