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MG MGB Technical - Differential Rebuild - Setting the pinion

Hi,

I posted the following message on the MGC board but haven't gotten much response. Since I believe the B differential is the same as the C maybe someone here can help.
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I had a bad bearing in the differential of my '69 MGC so I decided to rebuild the unit. I removed and discarded the old bearings and then took it and new bearings to a local British/European garage only to discover that a special tool, (18G 191H) to set the pinion, is normally needed (or maybe just the dummy pinion?). I am also being told that prior to disassembly I could have taken a couple of measurements of the pinion that could have been used to reset the pinion. As mentioned I've discarded the old bearings so it can't be reassembled and measured either.

So now that I have myself in this mess, I have a couple of questions.

1. Does anyone have the special tool 18G 191H (and or dummy pinion) that I can borrow, buy or rent?

2. Is there another way of setting the pinion on these? A key dimension, say from the axle center line to ????.
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If this was for my B I'd probably try to find another unit but not so easy to find a good C unit.

Anyway, I'd really appreciate any help I can get on this.

Thanks,
Jim
Michigan

James Budrow

The C was the same as the V8 at one point - 3.071:1, and rebuilds and conversions of 4-cylinder axles to this for V8s are quite common in the UK at least. Big thing to ship though.
PaulH Solihull

If you are only changing the bearings , reuse any shims that were installed under the pinion head. Bearing sizes are usually very accurate and it is unlikely to change the position of the pinion by any significant amount. The biggest problem I have had recently is that the new crush bushes that fit between the bearings to set preload are not to spec. I discarded the last three I purchased and made up a solid spacer and carefully shimed/machined to length to set preload. Check the diff thrust washers these can wear and cause knocking on load reversal . Refit the shims on diff side bearings as removed, and accept the preload as is. If you try to reset/reduce the backlash between the teeth this is when the unit is more likely to be noisy,
Jim
jim soutar

I agree. The difference in bearing measurements, in my experience, are almost nonexistent. You should be able to re-assemble the dif using the old components. In regards to the crushable collar, you can place it on a vise and gently tap the circumference a little at a time with a ballpeen hammer. With a set of calipers check the amount of distance that the collar "grows" after each revolution after hammering. When you reach about .020" you should be able to reuse the collar and set the pinion bearing preload to factory specs. RAY
rjm RAY

This thread was discussed between 22/08/2010 and 25/08/2010

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