Service, landing gear down, or while still hooked to truck?

Thanks for the added thoughts and opinions! I think I'll try it disconnected, as I'll only need to raise the axle about two inches to remove tire/wheel, while doing one side. I'll use my 8" high wood blocks under landing gear, so I won't need to use much of the landing leg extensions.

I jack under a U-bolt, using a hardwood 2x4 that is cut out, to just fit one of the U-bolts. I have a rubber padded jack stand to put under the axle tube near axle end. My axles are 5200 lb, and seem robust.

Jerry