My 63 Avanti,  RQ1695 has a 4.09 rear end listed on the build sheet and
dealer invoice. The tag on the diff is a 3.31. This is a one family car that
was not driven for the last 33 years and I would think that if someone
switched the rear end they would not be so detailed to install a ratio tag.
Is it possible the wrong differential was installed at the factory? I am
going to pull the cover and count the teeth to confirm the ratio. I hope it
is a 3:31, lots of freeways in So Cal.

 

Paul Katson