Differential Backlash Question

The pinion seal was seeping on my 2008 Goldwing with the Spyder, solid axle rear end, so I decided to change it today. It is shown as a Ford 7.5 differential in some of the information I've read. (I was talking at breakfast with Roadsmith and a Hannigan Trike owners and they both thought they had Ford differentials as well.) Even though mine was just a seep, driving down the road it seem to spatter the oil underneath the back end of the trike. Before I took it apart I marked the position of the drive shaft, the flange on the differential it bolts to, and nut holding flange on. I also counted the visible threads showing beyond the pinion nut but I didn't pay much attention to the backlash. I used a pneumatic wrench to remove the nut and to replace it. I can't quite get to the 5 threads showing that I counted but the nut seems to be as tight as it is going to get.

My question is what should the backlash or play back 'n forth of the pinion be? Maybe a better question is what is acceptable? I would say it it is about 3/16" on my trike. I went over and checked the driveshaft play on my F150, 4 WD with about 73,000 miles on it and it had about 1/4" back and forth. I've had the truck since new and it's never been abused, so I assume that's normal play.

I hate doing pinion seals ! Take it for a ride if it does not whine its good to go ?

Road Dog, I didn’t want to do it but while I was doing the heim joints and taking out/greasing the drive shaft, I kept looking at the moist wet pinion area and it bugged me. It was somewhere at that point I figured out that’s what was coating the inside of my new chrome rear wheels! Unacceptable. The trike had lacked good maintenance (something if I knew about trikes I would have seen) and I was going to find someone to do the things I wanted done but I either couldn’t find anybody to do it or they were backed into the summer with work. We have had such rainy weather this season I have been slowly picking away at things.
The last seal like this I remember replacing, was 50+ years ago and that was using a lift. That one leaked not long after I put it in so I finally went to a dealer who did it reasonably and it never leaked after that! On the trike I was sliding in and out like a snake slithering under a rock, so I’ll see if I installed the seal correctly.