Classic/Antique Car Repair: rear end gears, rear end gears, spider gears

Question
I have a 69 chevy ss 396 and my rear end gears are making noises and i was told that i need new gears .and the spider unit? and i was told that i could use the same sqush coller ? can you help ...oh  and i was told about shims whats that ?

Answer
ok step back a bit  how do  you know you need new gears ? are they worn or chiped teeth or look for a nice even wear mark on the round gear and on the the center gear (ring & pinion ) as they should mesh nice together do they have a lot of play or clank when you turn the drive shaft  if so you might need new gears . now what is this about spider gears if the rear is working and the spider gears are all ok you dont need them! as far as a squash collar yes you will have to put in a new one as you will have to use a tourque wrench on that big nut that holds the center gear in place , and as far as the shims if you take off the ring and pinion try to stay around the same thickness as it was but go about .5000 more  i almost forgot you might as well replace the race and bearings also this way it will be all done right .
 if you have no bad movement and the squash collar will hold the pinion into place when you tourque it. but first drain all gear oil and clean out all junk in the banjo as i hope you know that you must pull the axels out at least 6 inches and check those axel bearings and you might have to replace the seals- as if I were you i would replace them as I bet they are worn out if they are original.remember to put everything back the same way you took it out and you must use a torque wrench if you dont you will blow that rear first time out . ok so if you need any help ask me and dont forget to paint the back pan a nice chevy orange. prior to replacing it with a new  gasket ok
good luck
roger/bigw