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MG MGB Technical - lumpy gearbox

my 1980 roadster,s gearbox has gone really lumpy its a struggle to get first and reverse and some times there is no drive in reverse,there is no clutch slip,if anything it is a little harsh,the other gears are just very clunky,overdrive is working fine,also its over revving i have turned the screws on the carbs to nothing they dont even touch the base but it still reving at 1500rpm and when you take your foot of the accelerator the revs take an age to drop to1500
any ideas men
bryan cooper

You may have a clutch hydraulic problem - probably seals in the slave or master cylinder.

High idle speed - air leak somewhere on the carbs or manifold - or the fast idle screws on the choke cam are too far out.
Chris Betson

I am probably not understanding your "Lumpy" comments, but are you sure your tranny's gears have all their teeth?? Only reason I mention this is that I had a TR tranny lose a tooth on the counter gear and it too became "lumpy" and could be difficult to engage in reverse. Hopefully, Chris is more correct.
Bob Muenchausen

If reverse grinds even with the clutch fully down that indicates the clutch is dragging, which may be due to a hydraulics. Get underneath and chack the movement of the slave piston, it should be about 1/2" to 5/8". If it is, then any problem is internal to the clutch or gearbox/overdrive. No drive in reverse would bother me, this is a symptom of a failed overdrive, but maybe it just isn't going into gear.

Anything that stops the butterfly's fully seating into the carb throat can cause a high idle. This could be maladjusted linkage, throttle cable without the required amount of slack, butterfly not correctly located on its spindle, or fast idle screws as already said.
Paul Hunt

This thread was discussed between 11/07/2003 and 14/07/2003

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