According to the factory build sheet, RA is listed as the axle code. What does that translate to as far as ratio?

 

RA is 2.78:1 open rear, and it's the 8.5" Type O axle (same as used in the A-body cars except for the width) as opposed to the 9.3" Type O used on most full size cars. The 8.5 was used in the 350 powered Delta 88s only.

 

Appreciate response Joe.
I have the 350, so it's the smaller diff as you described. I know of a 1968 delta 88 4 Dr. W/455 2bbl. For sale. Assume that the rear axel would interchange with mine and be a better option to upgrade, as I am considering upgrading to posi and possibly
changing gearing to make the car quicker off the line. I recently purchased a 69 Toronado engine, which will eventually end up in this car.

 

Yes the axles interchange, however posi units and gear sets for the 9.3 are unobtanium. The 8.5 actually has marginally better aftermarket support since it's the same differential used in the Cutlass line, however even that isn't saying much.

 

It took nearly 3 years to find one when I was looking rear axle with posi for my -68 Delta 88. Finally I found one that was taken from -68 or 69 390 HP CHP version. However it's still 3.08:1, but works fine with upgraded 455 and TH400.

R. Sami