Hi: I hope you can help.

I have a 2000 chevy express 1500 custom van. When I put my my rear a/c blower on high it seems to go really slowly after 10 minutes. Any suggestions how to make it stay on consistently? Also, it feels like the drive shaft is coming part and it bangs on what seems to be the right center of the car. Have had this welded and mechanic says there is nothing wrong but it seems to be a severe problem that is getting worse.

Any ideas will be greatly appreciated.

Thanks in advance.

Susan