Rear Axle Gear Swaps 1968

Q: Rear Axle Gear Swaps 1968

Now for a question. I have 2:56 gears in my 1968 does anyone know what ratios I can go to without changing the differential? Is 3:23 or 3:73 a possibility?

A: Not with your differential case! Break out your trusty 1968 Factory Service Manual, and turn to the pages on rear axles. They have descriptions of the available axles, and a chart for how the cars were equipped with each ratio with the 2-letter codes stamped on the axle tubes. Mine (for 1969, same parts, different 2-letter codes) states that there were 3 differential cases (by ring gear mounting dimension, plus others for posi/non-posi), the first is for 2.56 and 2.78, the second is for 2.93, 3.08, and 3.23, then the third is for 3.36, 3.55, 3.90 and 4.33 ratios. This is for using original gears. The 3.90 and 4.33 used ONLY the 4-pinion locking diff case, the 3.36 and 3.55 posi used a 2-pinion case, or could be had in a non-posi type also. The 3.08 and 3.23 axles are not too uncommon, so you may want to look for one of those. I probably have a couple non-posi units kicking around here. Another choice is to see what the aftermarket offers, maybe Richmond Gear has something that would work with your differential case, although it might not go higher than 3.23.

Here I go again suggesting everybody get as much factory information as you can get your hands on! The factory service manuals are available in reprint, you can’t tell it from an original. Get it while you can!

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