Vacuum test, noisy gears

I am resealing the lower unit on an old mark 55 and have a few questions. In the process of the resealing, I noticed that the gears make a noticeable rattling sound when rotated, but if I lift the driveshaft (3-4 thou) the noise goes away completely. That's with reverse gear removed, so only the pinion gear and forward gear are involved. Of course there is no oil in the gearcase so it will probably improve with oil. My question is, is this normal, or do I have a backlash problem. I did not remove the drive shaft so no shimming was disturbed. 3-5 thousanths endplay is normal according to the book, so I don't know if I have a problem or not.

The next question has to do with pressure/vacuum testing. It passes the pressure test with flying colors. It will hold 20 lbs pressure without a problem, but flunks the vacuum test miserably. It will hold maybe 2-3 inches of vacuum, but that's it. I've done the oil test on the seals and see no leaks that way. Back in those days though, they didn't do either test and of course, this engine has only one seal on the drive and propeller shafts as opposed to the current opposing seals on shafts nowdays. The old seals were installed so as to keep oil in rather than keep water out, so I wonder if the vacuum test is a meaningless test on these old engines. I'm probably looking for someone with a lot of gray hair for these questions, but any advice I can get will be appreciated.

You have to lift the driveshaft to check gears.----That is normal.

Correct. Running forces the gears apart and they run smooth.

If the unit is still out, try pulling up on the shaft and rotating it.

Jeff

Thank you. I feel better now. Pulling the shaft up as far as it will go and rotating it eliminates the noise so i think i'm ok. I still have the vacuum question unresolved. Can anyone venture a guess on that issue?