The rear end of my 2000 Camaro z28 Automatic 4 Speed with 2.73 gears and traction control recently gave out so I installed a new rear end from a 2001 Camaro z28 A4 with 3.23 gears and Traction Control. Unfortunately upon deceleration the rear end started to "howl". I took the car to a mechanic were i was told it needed an entire rebuild. I was able to acquire a 3.42 gear and pinion along with a rebuild kit, which i took to the shop. I got a phone call from the mechanic telling me that the 3.42 would not be able to be installed as the Pinion gear was to short and I could only install 2.73 or 3.08 gears into the rear end. Im a bit confused as why it would not work as I gave them brand new pinion gear & ring along with a rebuild kit. Anyone know about rear ends that can give me some feedback?

 

A 2.73 rear end has a 2 series carrier which will work with 2.41,2.73,and 3.08 gear sets. Also available from aftermarket gear manufacturers for 2 series carriers are 'thick' gear sets of 3.42,3.73,4.10.
A 3.23 rear end has a 3 series carrier which will work with standard gear sets of 3.23,3.42,3.73,3.90,4.10,4.30,and 4.56.
It sounds like you're trying to use a regular 3.42 gear set on a 2 series carrier(your original rear end). If so,you'd need a 'thick' set.

for reference:

 

You can also buy a ring gear "spacer" with longer bolts, but that is not the ideal solution.