MBDale
Well-Known Member
My '79 R/T has the 318/904 combo. Will it have a 8 1/4 with 3:21 ratio? Or did the only 360 cars have the 3:21 raito? If the 318 cars came with 8 1/4 diffs then I'm going for 3:55 upgrade. Thanks!
My '79 R/T has the 318/904 combo. Will it have a 8 1/4 with 3:21 ratio?
I've never seen a V-8 F/M/J body with a 7 1/4", that's not to say there weren't any though. On the other side of it, my dad's S6/3-speed manual '74 Gold Duster has an 8 1/4" not the expected 7 1/4", go figure.
To find gear ratio, jack the rear tires up.
Place trans in neutral.
If you have a Sure Grip, spin the axle one revolution while counting how many times the driveshaft spins.
If the drive shaft spins roughly 3 and 1/4 turns, you have 3.21 gears.
If you have an open differential, only jack up one wheel.
Spin the axle two revolutions and count how many times the drive shaft turns.