The right rear wheel has a little slack in it, sort of like when a front bearing get's out of adjustment. There is no noise, just a little slack when the wheel is of the ground you can move it up & down. Is replacement in order or can I can I use the special socket to reset the preload on the bearing? It is my 83 300D Turbo.

Yes you need a special tool, lots of them including a dial indicator to set up the bearings. This isn't a DIYer project as a press & other items are required to replace bearings. Yes they are regular tapered bearings but set-up is very critical! This job is 3.5-5hrs at dealer with special tools!

I take it by your response there is just no readjusting it? I figured that since there's no noise associated with it that it may have been salvageable.

Yes if it's loose then there is a problem, as bearing area is sealed well & special lock nut is staked after 150+ftlb torque. Disassembly is the order of the day!

Thank's I was afraid of that. I just needed to hear or read it. I will have to find a decent tech in my area.