<VV> question about 1965 4 speed differential

[John McMahon]

On page 129 of the Corvair Basics book, it says "In addition, the splines 
internal to the pinion shaft tend to wear on a MT differential.  These 
should be checked visually using a strong light and by looking inside the 
pinion shaft.  The splines should be perfectly square, if they are "L" 
shaped or mostly worn down, the pinion shaft should be replaced."

I've got a 1965 4 speed, and I'm having a hard time figuring out how to do 
this check.  How does one go about looking inside the pinion shaft without 
taking the differential apart?  I have pulled the input shaft out, and using 
a flashlight I can barely see the teeth that it engages with all the way 
over in the transmission, but I don't think this is what I'm looking for.

Any help appreciated!

Thanks,

John McMahon
1965 Monza coupe 4 speed