Pinion shaft diameter

[Chris KC]

Roger, I think this is one of those topics where most of us are amateurs, and while we would gaily lash up our own axles we might hesitate to spout advice to others in view of the possible outcomes.

If you have either, there is sound advice in the 750 companion (Jack French, p169) or in Woodrow (section E4-13); also here http://www.vintageaustinservices.co.uk/page9.html - if you have not already consulted these sources I would strongly recommend doing so.

Looking only at your photo above, I'd venture that you aren't too far out. For my money I would try another increment of shimming, with the aim of moving the markings a little further toward the front of the car, and perhaps a fraction higher up the teeth? If the result then looks all wrong I would then go back to where you are and live with it. But I'm no expert...

One thing I would add is that it's hard to attain perfection with a part worn gear set. Above all else make sure it's all nice and free before you drive the car - any hint of tightness is likely to end in tears.

[Robert Leigh]

Roger, I think this is one of those topics where most of us are amateurs, and while we would gaily lash up our own axles we might hesitate to spout advice to others in view of the possible outcomes.

If you have either, there is sound advice in the 750 companion (Jack French, p169) or in Woodrow (section E4-13); also here http://www.vintageaustinservices.co.uk/page9.html - if you have not already consulted these sources I would strongly recommend doing so.

Looking only at your photo above, I'd venture that you aren't too far out. For my money I would try another increment of shimming, with the aim of moving the markings a little further toward the front of the car, and perhaps a fraction higher up the teeth? If the result then looks all wrong I would then go back to where you are and live with it. But I'm no expert...

One thing I would add is that it's hard to attain perfection with a part worn gear set. Above all else make sure it's all nice and free before you drive the car - any hint of tightness is likely to end in tears.

I have done this job on a number of Sevens, including the long chassis Ulsteroid that Paul Lawrence used to race in the VSCC. I have always set them up so that the blueing marks the centre of the tooth faces. With new gears this has proved completely satisfactory. With used gears I do the same, but if they prove to be unreasonably noisy I have adjusted to increase the clearance to what I guess is a 'worn' amount. My standard method is to mount the offside axle case vertically downwards in the vice, with the torque tube horizontal. This allows the weight of the diff and halfshafts to load onto the offside bearing. Only after setting the clearance with aid of gravity on the diff do I fit the nearside casing, and then adjust the nearside diff bearing. This method is quite quick and I have had no subsequent problems.

Robert Leigh

[Roger]

Robert,
Thanks for your encouragement.
My axle is the D type, so I am doing it with the Axle horizontal. I had read somewhere that the blue marking should be near end of the teeth, to move it further along to the centre I need to lower the pinion but have removed the shims and have nothing left but to shorten the spacer a few thou. This I can do as I have a lathe to make a shorter one.
The left hand thread nut on the pinion shaft was excessively tight, the two a/c bearings were a little stiff to turn, is there a way to set the preload on them? They were fitted with the load faces together.
My crown wheel & Pinion were used but very lightly worn, the wear looked very even and only reaching about halfway down the teeth so I was surprised by the noise I heard from the diff.
I feel that I am not far off being ok so may do a final setup with all the bits fitted and see what result I have.
At least I will know how to strip it down next time.

Chris,
Thanks for suggestions, I have both books, but it sounds easy when read about but the reality is a bit more confusing but maybe I am being too cautious.

Roger

[Bob Culver]

As previous, the contact seems somewhat toe and low. Moving the pinion out should raise the pattern and as pattern generally moves in the direction of the pinion this should also move pattern more toward  centre of tooth.

If the diff is unmodified adj should fall into available range.
 
If you start looking at the pinion teeth it all gets more confusing! The inner dia of the cw is regarded as toe end of teeth.

A final check ideally should be made assembled. A .002 shim varies the pinion; with all the altered pressures the cw is likely to move this amount on full assembly .

[Roger]

As previous, the contact seems somewhat toe and low. Moving the pinion out should raise the pattern and as pattern generally moves in the direction of the pinion this should also move pattern more toward  centre of tooth.

If the diff is unmodified adj should fall into available range.
 
If you start looking at the pinion teeth it all gets more confusing! The inner dia of the cw is regarded as toe end of teeth.

A final check ideally should be made assembled. A .002 shim varies the pinion; with all the altered pressures the cw is likely  to move this amount on full assembly .

So one shim added should get me closer to a good result, will try tomorrow hopefully.
Roger

[Bob Culver]

Hi Roger
I did not mean to imply just .002 would be the cure. Simply  that this is the typical adj increment and cw likely to move similar on final assembly, justifying a final check.

[Roger]

Hi Roger
I did not mean to imply just .002 would be the cure. Simply  that this is the typical adj increment and cw likely to move similar on final assembly, justifying a final check.

I understand your remark Bob,I have a shim but do not what size it is tonight, will try it tomorrow so will then know what my next move is.

Roger

[Bob Culver]

I am not sure if the LH pinion nut can be excessively tight. Often found to be loose. It is not clear what has been remewed.The ball pinion bearing was not everlasting and unless known to be newish prudent to replace, even if no detectable lateral clearance. If replacing make sure of at least normal tolerance, and not loose in housing. Others can advise about the a/c. Beyond my memory but original may have been with tracks of different widths with direct replacements not available. If the tracks and balls are perfect but some movement when clamped wide outer ring edge to wide outer ring, then the outer rings can be very thin shimmed to just eliminate play The assembly should turn very easily and smoothly.

With a/c races have to be always alert for assembly or adjustment situations that might lead to the balls being forced heavily into the tracks. Once sorted, the rh carrier bearing is a sort of datum, adjustment to accomodate different gasket thicknesses is in the lh side bearing.

[Roger]

I recently fitted a new pinion ball race which does not enter the diff housing to the same depth as the original. The amount of shims required now to fill the gap under the A/C bearings holder is about 1.5mm.
The marking on the crown wheel teeth is good so why the difference?
The bearing is the same as the one removed, I even cleaned the seating for the bearing, nothing else is changed.
What is the expected amount of shims normally fitted.

Roger

[Roger]

I have now refitted the rear axle to the car and briefly driven for a short test drive.
Unfortunately the noise is just the same as before the strip down, no more no less.
It is most noticeable at 30 plus in top gear, on the over run it is quiet.
Can someone explain why if the mesh is wrong on drive that it is quiet on the over run.
Also could the noise be from the gearbox transmitted along the drive shaft.
How bad do the bearings have to be to make such noise, they were all serviceable so not changed.
Any ideas much appreciated.

Roger