No. From what I have seen, the 31-spline dimples vs the 28-spline rectangular dish was not a reliable indicator until 1966 or 67. Production methods apparently changed around that time (see 28-spline re-design below) and there were a couple years of overlap where dimples could mean either. However, the rectangular dish always means 28 in every case I've seen.
Neither is "better" for most stock applications. However, HP and HD applications can use the greater strength of the 31-spline, which is generally rated roughly 20% stronger in both flex and twist (bending and torsion) than the 28. In HD load-carrying applications (trucks) the axle size also changed the axle housing tube size and thickness for greater load, as well as often including a larger flange (wheel) bearing. Just beefier all-around.Which is better, 28 0r 31 and WHY ?
well, I didn't want to rip the rear end apart to count splines so this was great help. I am hoping to find a center section already setup with a limited slip posi. something i could just bolt in. not sure if i care what gears are in it, although i dont think i'd want anything over 4.11 the way gas is. I have 3.00 in it now and get around 18mpg which i'm happy with, but since I only drive it about 3000 miles a year, gearing isnt too big a issue.
I didnt want to rip mine down since i am still able to drive it. not going to touch it till i have what i want ready to go back in.
+1. Remember, it only involves removing the wheel and drum, and then four nuts to pull the axle. That's it. You could be counting splines in 10 minutes. My 2-cents is that it would be worth the peace-of-mind when you're talking big money or big frustration for a mistake. Think of it as a practice run, and a check for if you will need an axle puller to get them both out later. Some stick, some don't.Better to check it now than to take a chance on getting the wrong punkin. Jacking up one side of the car and removing the wheel and one axle doesn't take that long. Chances are you will guess right with the info given, but there is always the chance you won't. It'll cost you a new axle gasket and an hour or two.
Mine's the same and they are 28 splines.