I am just rebuilding a Sierra diff and the Ford instructions tell me to have a 0.01mm backlash in the CW&P. But when I set it to this and then check the mesh with blue I find I have it meshing right at the end of the CW teeth which is not how I have been told it should be. If I set it so the mesh is bang in the middle if the CW teeth the backlash is much more.

So what would you do? Would you leave it meshing perfectly in the middle of the CW teeth or would you set it as Ford says and have the mesh at the end of the CW teeth??

BTW I managed to find a diff where the pinion preload was still very good so I haven't nor has it ever been taken out so this should be ok..

thanks in advance

jason

[Edited on 10/7/11 by Jason Fletcher]

Either way you set it up, it will be wrong. The mesh should be in the middle of the teeth, so it sounds as though the pinion has been set at the incorrect depth despite having the correct preload. I would recomend sending to somebody like Road and Race Transmissions to have it correctly set up. IMHO Ray

You have to adjust the shims under the head of the pinion versus the side-to-side movement of the crown wheel bearing housings until you get the 0.1mm lash while the teeth mesh centrally - if you see what i mean. It sounds like the depth of mesh is incorrect in your case so will need re-shimming.
This should be done with the gauge bar and block (shown in the documentation) but can be achieved by trial and error...

Ford used to sell a shim selection kit for this.


Guide here:

LINKY


You will need a crush washer and may as well change all the bearings while you're in there - they are pretty standard.

[Edited on 10/7/11 by Litemoth]

thanks gents, I guess the Sierra diff rebuild manual is wrong when it states 0,01mm back lash and it should read 0.1mm ?

I really want to get this done myself so I will contact Ford and see if the shims and maybe a new pinion nut are still available

Would the pinion need to move forwards or backwards to make the mesh closer?

Jason

[Edited on 12/7/11 by Jason Fletcher]

It is 10 microns (0.01mm) ...my mistake above. It's enough to allow for expansion when things heat up under load but should be able to be 'felt' as lash when moving the pinion on assembly.

Thicker shim = deeper mesh* = moving the pinion close to the centreline of the crownwheel.

* deeper mesh relative to the unmoved crownwheel. You can of course move the crownwheel away from the pinion (on the crownwheel's own axis so the depth of mesh remains unchanged - 0.01mm) but the result will be the point of contact will move - which is what you're after and shown by engineers blue on the teeth, test.

[Edited on 12/7/11 by Litemoth]