pinion head thickness

[rockyracoon]

my original 327 pinion had a thickness of 1.874

the new (410) FRPP pinion head has a thickness of 1.895.

so since the new pinion head is .021 thicker, would it be logical to assume that the correct pinion shim would have to be somewhat thinner than the shim on the factory(327) ?,thats what the MHD method would conclude,however in my mind even though the 410 pinion head is thicker than the 327 head,the 410 pinion is definetly smaller in circumference,so I cant see how the MHD would lead towards the correct shim. to me the circumference has to make a difference in some way.

 

[wmburns]

This was along the lines of what I was trying to say in a previous post. Please review the attached diagram from the Ford service manual. Note that the special tool allows for an accurate measurement of a KNOWN FIXED distance between the pinion bearing and the axle tube lines.

The actual thickness of the pinion head is not used.

The Ford special tool improves the outcome because it is able to correctly preload the pinion bearing and the carrier housing.

If we assume that the axle tube alignment hasn't changed since the car was built and the original set up was good, the only thing that can change the pinion shim needed are the pinion bearings themselves.

This is why more often than not, the original pinion shim works. Now things like different preload, how far the pinion races have been installed into the diff housing, and differences in manf can affect the pinion shim measurement.

I will be quite and let others chime in but I don't see how the MHD method can give the correct results unless the difference of pinion head thickness is taken into account. Further, this method assumes that the new pinion races/bearing are exactly the same (which is not always true).

 

[Quick99]

The pattern check never fails. Set it up with the old shim and go from there.