Differential Set up Trick

I have been trying to find gear marking compound to check the GTCP (gear tooth contact pattern) on a diff I have that needs a new pinion bearing so that I can reuse the gears and not have any problems down the line. None of the parts store carry the good old yellow marking grease and I did not feel like placing an on line order and I do not like Prussian Blue so I improvised. BUTT PASTE to the rescue!!.

I used some Boudreaux's Butt Paste and a little bit of chalk box chalk ( the kind that is used in construction). You can use any of the diaper rash creams that are zinc based ( Desitin, Burt's Bee's etc) find one that is higher in zinc and thick for best results. You can also use powdered food dye to color the Butt Paste if you have that around.
The chalk comes in a lot of different colors so you get to make your own custom color for setting up differential GTCP's. The best thing about this is it cost me $0/zip/nada. I had the chalk and the wife had some Butt Paste left over from one of the **** monkey's. You can use the paste with out any coloring if you want just make sure that you use the thicker Butt paste Or if it is a little thin add some chalk to thicken it up.

well, it is a Rear-End after all

I just use white lithium grease. Works great.

Welding supplies dealer sell metal marking paint in different colors called "Dykem". I find nothing wrong with prussian blue if you place a pry bar on top of the carrier and rotate the pinion by hand. It leave an impression you can see and read.
Newer shim pack are not the old-school cast iron, but shims at 0.02". The trick is to install everything, get the pattern correct and back-lash. Then install two feeler gauges at 0.02" then install 0.04" on each side for carrier bearing pre-load. I prefer more valley and 0.05" black lash compare to the 0.08 - 0.10" they note in books. The diff will wear and open up under load anyhow. Never had one fail and running mine that way now with no noise.
But that's just me. Do what you want.