How much slack for ECSB center support bearing?
 

I took my truck into the shop a few weeks ago to have the center support bearing replaced because it had alot of play in it and I could hear noise when I would back up.

The shop said it was the middle ujoint in very bad shape and that it was close to seizing up. They also said the support bearing looked fine.

There is alot less slack or movement side to side, but it still moves 3/8" either direction. Its the rubber isolator that moves that much, not the bearing itself.

Is this much play normal?

As long as it's the rubber moving yes, that's what it's there for... Just make double sure it's not the bearing itself.