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MG MGB Technical - 1st Motion Shaft

G'day. Just got the g'box off the engine, and I can 'waggle' the shaft by gripping it at the flywheel end. With the side cover off I can see the bearing move between the inner and outer races. Is a small movement normal or am I about to strip a gearbox down for the first time in my life?

Tony OIiver

Replacing the First Motion Shaft bearing is not all that difficult --- IF you have one or two good workshop manuals.

There's a certian amount of getting into the mainshaft area, fooling around with the roller bearings and a few other things.

Withan above basic "take it apart and put it back together" knowledge and confidence it is a do-able job.

Just take care to photo and /or make notes of the progression of dismantling, which will help very much in reassembly.

Most important -- take your time, read the manuals and look at the exploded parts diagram to figure out how it's all put together. It's not a job for the fain of heart.

good luck ----glg

A small amount of movement is normal at the end of the shaft when wiggled. When attached to the engine, the bushing in the crankshaft supports that end. The amount of movement is somewhat subjective. Grip the shaft right at the cover and try moving it in or out as well as up and down. Watch the bearing as you do this, if the center race of the bearing moves in and out or up and down more than a about .003", you have a worn bearing.
John H

There are some shims between the front cover and the front bearing. It's not unusual for these shims to be damaged. The procedure for calculating the required shim thickness is in the Haynes mgb manual on page 126. The information is also in the gearbox section of the shop manual.

Clifton Gordon

Thanks gents. I will have a closer look at the g'box. I kinda thought that any movement would be magnified without the front of the shaft being held in its bush.

Tony OIiver

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

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