Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Adjusting the pinion in the differential


I have been restoring the gearbox. It did not look too bad, but it clearly had done quite a few miles. Just want to make sure the differential is in good shape. The gears look ok, but now that i have it out, it would not hurt to give it a good inspection. In the WSM I can see some drawing and I read the text a couple of times, but it is still not clear to me.

I understand I have to align the pinion with respect the the crown wheel, and adjust the preload.

First I adjust the position of the pinion. There is a block to check the pinion position. From what I understand, I need to measure the distance from the top face of the pinion to the part of the housing where the bearing outer race sits. I put the whole housing on the drive flange and put a micrometer foot on the (now) top face of the pinion and the tip on the lowest part of the bearing housing.

I will need to check the marking on the pinion head (as explained in the WGM) but I will need to know the thickness of that 'special block' as it is called in the WGM.

I guess it is the same as putting a metal ruler on the bottom of the bearing housing and measure the distance from the ruler to the pinion top face. But what does that distance need to be.?

-- Paul
Paul van Adrichem

I don't know thickness of the metal block. That said, if it ain't broke, don't fix it. The original rear axle in my car ran a quarter million miles with only regular oil changes and some new seals. It is one of the most robust parts of the whole car. I have never known a ring and pinion gear to get out of alignment or ever wear out, except for running with no oil, in which case the whole assembly will be shot anyway.

You can R&R the differential and crown wheel assembly without disturbing the gear alignment. You do this when changing the sun gears for different splines. You can also change the front seal and/or R&R the halfshafts, or R&R the complete differential assembly from the axle without disturbing the gear alignment. If it runs quiet, don't fiddle with gear alignment.
Barney Gaylord

Hi Barney,

Thanks. When I took it apart (never drove it before taking apart) there was normal oil in the differential, and no ugly pieces of metal. I'll follow your advice, just put it in and try. Other than the gear box, it is fairly accessible in the unlikely event of failure. (It will take another year before I can actually run it.)

-- Paul
Paul van Adrichem

This thread was discussed on 02/11/2011

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.