Cat back replacment (How to remove)

**mgolin** · 11-20-2010

I have looked through a lot of threads, but most are on best sound or best cat back.

I just would like to know how to remove the cat back on 98 Grand prix.

Previous cat backs had a stud on cat side, and nut on resonator side.

The stock cat back looks like a flanged nut on cat side that is welded on. However there is no nut on the resonator side.

Has the nut just rusted off, and if so, why is the resonator not loose.

thanks

**Vlad0691** · 11-20-2010

There should be flanges with 2 bolts on either side right before the resonator.

**mgolin** · 11-20-2010

Yes two flanges, one on cat, one on resonator. The bolt head is on the cat side for sure. No nut on the resonator side, maybe threaded flange. My best guess is bolt head is welded on cat side, but then there should be a nut on resonator side.

If I cut off the head on cat side I assume all will slide off unless it is pressed in which means I should cut off the resonator side.

Any feedback on which side to cut cat side or resonator side.

**Silver GTP** · 11-20-2010

The two flanges are not a slip fit. They but up against each other with a gasket in between them. If you only see a hex head on the cat side, then it is either a nut attached to a stud from the resonator side or a bolt threaded into the flange on the resonator side. Mine had the resonator replaced before I bought the car so the flanges had holes on both sides with a bolt and a nut holding them together.

**mgolin** · 11-20-2010

Well I cut through the hex head on cat side, and it is for sure not a nut (no thread). On the resonator side I ground flush to backside of flange, and it must be threaded into resonator flange as the flange will not break loose.

I will keep grinding and cutting till it comes loose, just a very strange joint with no clearence holes in the flanges.

When done I guess I will have two holes in each flange.

**mgolin** · 11-20-2010

I ground down flush with flange on both sides, and still do not see a hole. You can see the ring of the bolt on both flanges, but will not break. Guessing it is a pressed in stud on one side and threaded flange hole on other, but no way this could be.