what does the gear shaft do?
 

...the shaft between the joint cups...

I took it off b/c I got a misaligned hole in of my metal joint cups. The car works fine.

front or back?
 

Are you talking bout the front one or the back one?
Also with AWD or w/o?

RWD

if your talking about the black thing in the front of the car, i think all it does is push the pegs and keep them from falling out when the wheels are off.

Do you mean the shaft that goes through the rear drive axle and the differential, the metal pin that goes into the hole in the center of the shaft?

yes boxcrash

hmmm
 

I could be totaly wrong and have not looked at it but I belive it is just there for the differential.

I belive it aids in the operation of it and to reduce play in whatever direction it is suppose to in.:D :rolleyes:

i agree with boxcrash. i think it prevents the diff from wobbling around too much. i drove a bunch of times without it tho and nothing different.

Oh great, so I can take it out an save .0000000001 grams! :p

lol

more weight off this heavy drivetrain;)