Jacked up the passenger side and grabed the rear wheel at 12 & 6 and have quit a bit of play.  Do not really have any at the 3 & 9 position.  Thought it was the u-joints, so I changed them out today on both sides and still have the same issue.  The driver side does not budge.  Are my bearings bad or what can cause this? 

A worn diff yoke can cause this. The play is from the yoke moving in/out of the the diff when you move the tire/wheel.
Usually, worn bearings will give you play in both directions(12/6 & 3/9). If you can get a helper, crawl under and watch the yoke while the helper moves the tire/wheel. I bet you see the yoke moving in/out.

If the diff yoke is worn, you will see some movement at the wheel/trailing arm end too, but what you'll see is the entire trailing arm/spindle/hub moving...not play in the bearings. You'll want to check for in/out movement at the diff end, where the yoke goes into the diff. There will always be some movement there, but if it is enough to actually feel it from the wheel end, it's prolly too much.
Due to the design of the rear suspension, when the diff yoke end wears, there is nothing to really keep the trailing arm from having any play in it with the rear in the air. You won't be able to notice any 3-9 o'clock play, since the t-arm is anchored at the front by the bushing/bolt, and at the rear by the strut rod. But...when checking at the 12-6 o'clock position, the wheel can move in/out, since the yoke wear will no longer keep the play to a minimum. The bottom of the wheel is still anchored by the strut rod, but the top uses the yoke, and half-shaft as a part of the suspension, so any wear in the yoke will cause play. How much is too much has been debated for years, and I know of no published specs for the allowable amount of play.
Hope some of that makes sense.

There is always the possibility of having bearing play, too...don't get me wrong. My point was that IF the bearing has too much play, you will get movement from checking at both the 12-6 position AND the 3-9 position.

IF you have movement at the wheel end, and you're sure the whole t-arm is not moving, then you prolly do have some bearing play. Removing the halfshaft will make it harder to check, since the t-arm itself would be able to move more.
If you can actually see the flange on the wheel end moving, how much play does it have? Technically, there should be NO play at all in the bearing assy. You can get by with some, but usually not forever.

You should also take a good look at the bushings on the strut rod. Worn bushings could also allow some movement of the t-arm.
Adams' Apple2011-07-17 19:32:54

I just experienced the differential yoke play on our '74. I ordered some new Yokes from Eckler's now to install them.

This is what was discovered on mine when I went to put first set of new tires, both side would go in and out. Required differential rebuild. This was something I did not attempt, check past post but not easy. You should replace with hardened yoke to prevent this from happening in the future. If I understand the cause it is from the yoke going in and out and impacting the pumpkin and wearing the ends of the yoke. eventually the keepers can come off and the yoke come out not good. Experts chime in but I would get a new or rebuilt diff. it takes special tools to set up the clutch packs inside? I have a pdf file on how to rebuild if needed. rraider12011-08-12 09:39:46

  Ya picked a FINE time to leave me LOOSE WHEEL.   Carlisle is coming.

Yeah, we gotta get these cars in shape for the big show! Let's get busy!!!!