Help! 30 or 31 spline?

[superbird77]

I need some help, i am purchasing a new Eaton TrueTrac diff and need to know how many spline my axles are. I guess its either 30 or 31. I have a 1969 roadrunner, 8 3/4 rear, 489 case, 3:23 gears, no sure grip. I don't have access to the rear end otherwise i would check for myself. If anyone can help it would be appreciated. Thanks!

 

[NJRR]

Can you get under there and check the numbers on the case of the trans and tailshaft housing? That might help. My GUESS is that if it's a 69 A833 and a 23 spline input that it's a 30 spline output. I'm doing a 727 to 833 swap now and that's what my research indicates.

 

[Supershafts]

Should be 30 spl, only way to know for sure, pull and count

 

[bm02tj]

Wait till you have diff apart if any damage or wear on axle buy largest spline size and new axles
Bruce

 

[Cranky]

30 splines for that rear....

 

[68GTX4SPEED]

30 splines for that rear....

x2 all original are 30 splines, 35 splines aftermarket only available with spool.

 

[superbird77]

Thanks everyone.