lots of 8 3/4 ????s

[68gtx]

ok i got quite a few questions here,

wanna build an extra third member for my car so i can swap out gears failry quickly, i bought a bunch of 489 cases, some complete some just the cases...
1st question, one of my compete units , has a very fine spline on the pinion where it meshes with the yoke, all the others have a very corse spline , didnt count them but like a 10 spline to a 30 spline, whats up with that?
secondly the units that are complete have a shim between the pinion bearing and pinion, i know to swap this over to the new gear set when changing gears , but what do i do if i go to build up one of the cases that is bare?? how do i know what size shim to use?

thanks in advance

 

[oldkimmer]

.................OK, 69 and 70 has course spline[10].....71-74 has fine spline[29]...the factory pinion shim is just a starting point, its almost always + or - from the factory shim when setting pinion depth.......kim..........

 

[1948 santa]

Only real way to find pinion depth is to use Miller tool set C-758 which can be bought on line not cheap.

 

[Garys1969RR]

Yes assembling the ring and pinion into a case is a whole science in itself. You not only have pinion depth, but also pinion bearing pre load is critical. Some use a crush sleeve, others use shims. And dont forget ring gear to pinion backlash! Good luck!