how do I determine what axle my 1970 Plymouth Road Runner has?

Answer 1

if it has a Hemi, Dana 60, any other motor the 8.75.
pull the cover and look on the ring gear for date of manufacture and ratio. it will be like 4 70 41 10, meaning April 1970 with a gear ratio of 4:10.

Answer 2

Are you trying to find the axle ratio, or the basic axle design? Axle ratio is normally stamped on a metal tag. You'll find the tag on one of the bolts holding the cover on, or holding the differential to the axle if it's a 8 3/4" axle.

As for axle type, a Road Runner is most likely to have a Dana 60 or Mopar 8 3/4" rear axle. The 8 3/4" is easy to spot - it has no differential cover on the back, but instead has the differential in a removable carrier that bolts on from the front of the axle. The Dana 60 will have a cover on the back with 10 bolts, shaped like a lopsided hexagon.

I suppose it's possible that someone may have put another type of axle in there. You never know what somebody may have done to a car that's over 30 years old. Other Chrysler axles all have covers on the rear. They include the 7 1/4" (9 bolts, circular or octagonal cover), 8 1/4" (10 bolts in a tall oval), and 9 1/4" (12 bolts in an octagon). If it's been a drag car, somebody may have even put a 9" Ford rear axle in there. Sometimes you never know what you'll find in old cars...

Answer 3

This is easy.
block all your wheels so the road Runner wont roll. Jack up one rear tire, mark the tire in a spot then mark a spot on your driveshaft. put it in neutral and count how many times the driveshaft turns for 1 tire rotation

Answer 4

If there is no tag pop the rear cover off,it is stamped into the ring gear

Answer 5

trere is a tag on one of the differential cover bolts