Drivetrain Cracked Aod Driveshaft Dampener

Back story: Car started having serious vibrations. Took it in to the shop and they replaced the U-joints. Drove it home and the vibration was significantly reduced, but now on deceleration I could hear/feel a soft grinding/vibration. I was slammed at work so couldn't get car back into shop right away. A couple days later the grinding part of the noise went away but I still felt a slight vibration at times. There was no heavy driving during this time just to and from work on city streets. Now a week after I had the U-joints replaced the mechanic showed me this dampener on the driveshaft (DS) is cracked. (image below is of part, found on another thread, not my part that is cracked)

From searching threads I've found the driveshaft (DS) dampener is found only on 4-cylinders with AOD. My car 1991 GT AOD has a dampener which is cracked.

My mechanic's DS guy says the dampener can be removed with no problem. I'm hesitant to remove anything that is a dampener without understanding its function of the whole.

Hopefully you guys can help clarify some questions.

1. Did a factory 5.0 w/ AOD come with one of these, or was it only the 2.3?
2. If the 5.0 did come with one, why did the AODs have one and not the sticks?

Thanks in advance,

Awesome, thank you for all the quick replies. I'll start digging in the threads to see how to replace the driveshaft.

Possibly related question, for as long as I can remember my stock AOD likes to "buck" on deceleration when down shifting. It's not consistent just occasionally. Though sometimes it also does it on acceleration. Example; low rpm then slightly accelerate up a hill. Could this be attributed to anything other than the U-joints? Which have now been replaced.

Thanks again.