Tom- this isn't an easy DIY, but there are several threads on it if you search. I had a race shop change out the diff bearing on my Z racecar, but haven't done anything on my Z streetcar yet. I haven't seen a "trail of black" under either Zs diff on the floor. You may have another problem going on there.
It was actually the rear differential bushing, the trail of black doesn’t hit the floor it just stains under the bushing in the rear sub frame, the liquid filled bushing. Was able to remove it with an air hammer, the 2 front bushing of the differential came out easier, the urethane bushing went in easy. The tool Z1 sells may make it easier to remove if you are working on the ground, but if you have a lift and air tools then it sucks less. I don’t have a diff bearing issue.
Also making it easier was to remove the passenger rear section of my exhaust, just 1 V clamp, it’s a Motordyne shockwave, allowing the space needed.
Thanks for responding to my post, I was on vacation and couldn’t respond sooner.
