I just swapped my differential out from a 2.73 to a 3.42. After driving in circles for a bit, I noticed that there was a noticeable chirping sound when the car was coasting. At first, I thought (and hoped) it was just the brake pads wearing in(I just replaced those, too), but the noise goes away when acceleration resumes, or if I push in the clutch pedal and take the load away.
According to all the information I could find on here and other sites, the rear end was set up correctly. Right at two lb/ft of preload, .006 inches of backlash, and the contact pattern was in the middle of the gear teeth.
I haven't put in any limited slip additive, just Mobil One 75w90.
Additionally, I crawled underneath to check and make sure nothing was loose, which it wasn't, but noted that the differential was fairly hot to the touch. Not scalding nor so hot that I couldn't keep my hand on it, just hotter than it's surroundings. Is that normal? Thanks.

 

Contact pattern isn't usually set up for the middle, because it moves when you accelerate, especially with your spindly 10 bolt pinion, which is like a limp dick in your rear end pardon the pun, so you set it more towards toe cause it will move towards the middle under load. Chirping might just be slipping noise if you are driving in circles, though. If it is doing that on straight line decell, then you missed something and you might have to pay more attention to your coast side pattern..

 

If it is chirping when turning, you need the LSA.

 

Thanks for the insight. I went ahead and put some of the additive in, $10 is worth a shot at not having to tear it all apart again, and it got quieter for a bit. But then it just let out a grating metallic shrill(again, when coasting in gear), so it's all going to have to come apart again. I think I'll go ahead and buy new C clips while I'm at it, mine were a little worn with noticeable grooves and I remember reading something here about them potentially causing noises. My spring break is over, now, so it'll have to wait until next weekend, but if I run into any more problems, I guess I'll just ask then.
One parting question, though. When I put the paint on the gears and spun them back and forth, the paint wasn't really pressed off the teeth to where I could see the bare metal underneath, but I could see where contact was made and subsequent marks where paint was then transferred to unpainted teeth. Is there any relevance to that?

 

You need to find a way to load it while turning it or you won't get a decent pattern. Get someone to restrain it on the axle side while you turn the pinion.

The stupid c-clip system can wear the metal parts because the hardened clips have a sharp side to them (stamped parts) and if they are installed sharp side out, they can grind their own clearance grooves into the diff. The VE engineers that signed off on that weak-as-glass cost-reduced design should have a pox on their spotted souls.