Any ideas on this Vibration issue?

So I am having some vibrations at certain speeds. It started about 2 weeks ago. I had the U Joints and Carrier replaced 08/12/2020. The vibes came in pretty rough and had a squeak with it. I assumed it was the carrier or u joints again. Further inspection and I had some good play on the drive shaft so I replaced the carrier again. Either I ordered the wrong part or I am just bad at repairs. After replacing the carrier myself the problem persisted.

I took it to a shop and they said the drive shaft still had a lot of play and replaced the carrier again. 3rd times the charm.

Got the truck back today. Still feeling vibrations at 0-30 and then it stops. Comes back at 65-75mph. I only feel it on the accelerator and when I am coasting still in drive. It feels like it is towards the front end but I can't really determine where exactly on the truck. Before I took it to the shop it was definitely from the rear. No vibes at idle, no vibes in reverse or neutral. The balance and tires are all ok also.

Any ideas on what else it could be?

 

Could be a number of things. Check to see if a weight came off a wheel/ tire or the driveshaft itself. Also, the driveshaft could be off center. The cb can be moved slightly left or right. You can tie a string on the front zerk and rear zerk to see if it’s straight. See my diagram below.
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Also, if yours is a 4x4 try putting it in 4WD and see if the low speed vibes go away. If they do it’s the needle bearing.

 

Time to switch to a one-piece driveshaft

 

I've been considering and heard about this. Is it worth it?

 

The technician had brought up the front half of the drive shaft looked newer - suggested it may be out of balance or incorrectly balanced. I'll give the 4WD a whirl and see if anything changes.

 

They can be pricey. Check out Tom Woods, seems to be the top choice. U-joints and carrier bearing should have solved your vibration problem if installed correctly and the issue was coming from the driveshaft, that is, if it's properly balanced.