I can't seem to remove the 2 rear studs/bolts (that connect the cat to the muffler pipe).

I was able to remove the nuts at one end in order to remove the catalytic converter from the car, so that's not the problem. My problem is I can't remove the stud from the rear flange of the cat. I understand the nut on the flange is welded on, so you can't remove that nut (unless you break the weld). I'm trying to re-use the studs for my replacement cat.

It seems you need a 13 mm wrench, which is borderline too loose and seems like it's going to strip the damn thing. I used PB Blaster and it still won't budge.

How in the world do you get a good grip on the stud to try to unscrew it?

 

You need a deep socket 12mm wrench, if you are trying to get the two spring nut assemblies out, and one of the studs should come with it. Did you already remove these nuts?

 

I haven't looked. Would vice grips fit?

 

Ok, figured it out! 13 mm is borderline too big and will strip the damn thing. Dirt_Nasty mentioned a 12 mm BUT that is too small.

The correct size is a deep 1/2" socket. It fits perfect and snug. I was able to remove the rear studs! I used a long torque wrench with the socket to get more leverage.

I have no idea why everything else is in metric system except for the rear cat studs. Ridiculous.

I hope this will help others in the future.

 

1/2 inch equals 13mm. Same size

 

I tried vice grips. They slipped.

 

But I tried a couple of different 13mm open end and box end wrenches. They were a bit loose and started stripping the nut. Maybe you might get away with a 13mm in some other applications but I'm telling you, they will not work for this. Unless multiple manufacturers produced the same defect in 13mm , I believe that 1/2" is very slightly smaller. The 1/2" fit perfect with absolutely no give.

 

Depending on the manufacturer some wrenches/sockets have more tolerance than others. We have some German made wrenches (for wrenching on HPLCs) at work that JUST fit the sized nut they are designed for. We also have some french made wrenches that are MUCH looser. (insert Franco-german sexual innuendo here)

 

http://www.engineeringtoolbox.com/in...ion-d_751.html


Not quite. 1/2" = 12.7mm

Check chart from above site address. Size matters.

 

They are splined, they won't 'unscrew'.

 

I got mine out pretty easy. I forgot it was a 12 or 13mm. it should be 13mm.

mind if I ask what brand of socket you're using? cuz el cheapos tha sells for 99 cents usually are a bit "off"

I tried both Craftsman and Duralast(Autozone) and both works fine. the el cheapo I got from my father just slips.

 

snap on FTW :P craftsman is good for the warranty. I have returned 20 and 30 year old tools my father gave me to a sears before and got a replacement. When they say lifetime they really mean until the company fails.

 

^+1 yep Snap on FTW.