How to remove slack adjuster with a weld clevis on push rod.

Since the slack will not adjust, you can't back it off to clear the yoke/clevis either. Once you have the clevis pins out, you would have to just unbolt the brake chamber from the mounting bracket so the slack adjuster will clear the yoke/clevis.

 

You could just cutoff wheel the slack adjuster. Depending on what you have, you might want to replace both slacks and cans while you are at it.

 

Ya try heating up the slack to soften up the old grease to get it to adjust? That would be my first step. Just a propane torch or even a heat gun might work.

If no luck, then break out the tools of destruction. cut-off wheel or O/A torch.

 

Manuals are not legal to install on a newer truck. I forget the exact year, late 90's maybe. Shop around, you can get them a little cheaper at parts stores.

I found it:
http://www.gpo.gov/fdsys/pkg/CFR-2001-title49-vol4/pdf/CFR-2001-title49-vol4-sec393-53.pdf

October 20, 1994 is when auto slacks were required. If your truck is older than that, it's legal to replace with manual.