Driveline vibration

I replaced the center bearing on a ‘72 Pete with 12513 and 4.11 rears. It has 1710 series full rounds. The old center bearing was a Spicer 210121 that was still in great shape no play and smooth rolling. Just the rubber was toast and had over 1/2 in. of movement in it. The bearing pulled off easily in one piece with a puller and gave none of the usual fits. I replaced it with a Meritor 210121-1x self aligning bearing and now have a very bad vibe thru the floor up into the seat and steering wheel between 40-50 mph. Seems to be worse in 7th od cruise at 45 mph at around 1700 rpm.

The yokes were marked and put back in the same place and I marked the u-joint caps to try to get them back in the exact same spot. But i keep thinking they got swapped due to a “shell game” under the truck.
When I did the bearing replacement I only separated the shaft at the bearing yoke and removed two u-joint caps to do so. Did not touch the trans end or diff end. Ratchet strapped the two shafts up and didnt rotate them.
The yoke nut on the bearing stem required 550 ft. Lbs. but due to tight clearances I could not get a torque wrench on it to turn it so I had to uga duga with 3/4 gun. If any thing its over tight and not loose. U-joints only have 37,000 miles on them and are solid. The grease was still clean.
The yoke phasing is correct.

No vibes with bad rubber and now vibes with the new tight stiff rubber?
That is the only change.

 

@pushbroom. They are lined up. The splines are coarse on a 1.9 inch shaft so one tooth off is a big difference. I actually triple checked it. Lol! I’m pretty ocd about that kinda stuff.
@spsauerland. Meritor put a sheet of paper in the box that said the new design has the slingers built in and there is no need for extra external ones and to remove the old ones off the shafts when installing. I fretted over this and even checked the position of the old slingers before I removed them and they have no clearance around that bigger rubber lip on the bearing. I removed them without damage and bagged them for future use if need be.
As far as shims there were none on the old one and it didnt look like any were needed. The splines did not protrude out past the end of the splines on the yoke.

 

Yeah. I know. Fun times to be had.
Crank damper is 6 months old. Front Engine mounts are green poly in good shape. Rear mounts are old school solid no rubber so you always got that fuel “pulse” vibe thru them when heavy footing but this is different.
It has the old 70’s air trac. Good shocks and rubber bushings on the tracking bars. I checked ride height. Its good.
I need to take it around without a trailer and see if it changes things. Then put it up on jacks and start checking everything bolted on. Maybe it needs a tire or two.

 

I know they do on my old Pontiacs.
This makes me wonder if the new rubber being used in the bearing is some kind of poly. It has a different feel to it than rubber. Kinda harder and greasier like poly feels. There are less holes in it and they are smaller and farther apart then traditional.