Nope, only way to tell is under load with the gauges and monitoring pressures and vent temps. In other wordsyou'd need a working clutch first.

Rear End Issue
 

Well, a little update on the Mach. I have been noticing a noise coming from the rear for a while now and as a result have been driving the car almost never. it has been getting louder and causing a vibration in the car. Took Ron for a drive yesterday and he said right away something was wrong. I opened up the rear and the oil looked ok, but it had only been about 5K miles since a change so that was no surprise. I turned the tires and inspected the diff. I noticed that the spider gears seemed to have a few more chips in them since last time but did not see anything in the oil (found some chips on the magnetic plug though). We took backlash measurements and had a variance from about.12 most of the way around to about .01 at one point. Took some other measurements and we have a problem. We did not have time to take the carrier out since we are working on my dad's Mach so the car will be sitting for awhile. Need to prepare for the worst so I am going to look into options.

Let me clarify this a little. We checked the backlash which was .012 on the first tooth we check. Then I turned it a few teeth and check another tooth and it was .008. I turned it a little more and and the backlash was .000. At that point you could feel friction when trying to turn the carrier. I then had Adam check the vertical runnout which was 0.002 which is good but when he check the horizontal rumour it was 0.03 which is way out. I have a feeling the ring gear was pushing the carrier over so we need to test it without the ring gear on the carrier.

What he said.