When I shift from reverse to drive or the other way around there is a big thud like there is play or slack in something?!?! Anyone?!?!

 

Have someone stand next to the truck and look underneath to see if they can identify the problem. Does the truck jerk unnecessarily when you change gears?? If so, have someone watch the drive shaft so they can see if the extra movement is uniform throughout and consistent with the movement of the shaft or if there is just a lot of play in the rear end. Also, when shifting from R to D or D to R, are you waiting for the truck to come to a complete stop before shifting???

By the way, welcome to the forum!

 

I just had the rear end apart and everything seemed like it was in great shape with no worn gears or free play. Thanks for the welcome!!

 

U joint, carrier bearing rubber, loose bellhousing bolts,torn motor or trans mount, rear spring shackle or U bolts broken, loose lug nuts, rear U joint bolts coming loose.
some things to look for.

 

I have an 05 Silverado 1500 LT 4x4 Ext Cab. I just bought it a week ago, and i already had to replace the drivers side front wheel bearing assembly. i noticed the infamous "clunk" sound, but what type of "play" in the shaft is everyone talking about...Horizontal and vertical play or rotational play. i left the truck in park, and there is no horizontal or vertical play at all, in park or neutral, but when the truck is in neutral i can rock the shaft and the whole thing rotates just a little...in gear nothing. please help, this is my first silver ado!

 

It is rotational that you check for U joints. In nuetral you should be able to roll it, and not in park.