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Discussion Starter #1 (Edited)
I hopped in the truck this afternoon, heard a rubbing sound,
looked under the truck and the 3 bolts on the flange between the cat and muffler look like they snapped... ???

The muffler was hanging against the driveshaft.

Stock truck, no mods, 38,000 miles

Is this a freak occurance or has anyone else had this happened

Is there a Recall? TSB?

2008 LMM 3500 Dual extended cab

Thanks for any heads up,

Rich
 

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Quite common. Either your dealer will fix it, or fix it yourself.
 

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Or 3 new bolts and a few minutes with a punch and hammer to knock the old ones out. Total cost? $.50-.75 and about 5-10 minutes of your time.
 

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Or 3 new bolts and a few minutes with a punch and hammer to knock the old ones out. Total cost? $.50-.75 and about 5-10 minutes of your time.
I actually broke those off under my own strength. They're garbage. I couldn't even hammer them out with a 5lb mallet and a chisel.
 

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I hated removing my exhaust with those damn bolt though. It's like my truck didn't want me to perform surgery on it so it fought back with those bolts...
 

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Thats not the cat in front of the muffler its the DPF and the heat from regens frying those bolts time after time is what makes them fail.Just one more reason to can the DPF.Almost at 50K miles on mine and think a 70K the warrenty can go along with the DPF.
 

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Discussion Starter #8 (Edited)
Thanks for the replies.

No Good on the DPF delete, I'm in New Yorkistan.

I actually broke those off under my own strength. They're garbage. I couldn't even hammer them out with a 5lb mallet and a chisel.
3 years and 38K miles, I certainly agree they're garbage, maybe the high temps corrupted them early?

So, if you couldn't hammer them out with a 5# sledge, how did you finally remove them?
Did you have to drill them out?

If I take it to the dealer, would they or have they upgraded the bolts?

I was thinking of using stainless.


Thanks again,
Rich
 

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Discussion Starter #9
Thats not the cat in front of the muffler its the DPF and the heat from regens frying those bolts time after time is what makes them fail.Just one more reason to can the DPF.Almost at 50K miles on mine and think a 70K the warrenty can go along with the DPF.
Looks like I wrote my last response while you posted, Sorry about the "cat", old habit from the gasser days... :eek:hno

I had the same thought about the heat, maybe they should hire some engineers and put some fore thought into the design.... sheesh...
I mean , bolts snapping at 38K and 3 years, :thumb
 

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Mine broke at 96000 miles while doing 65 down the highway. Mine nosed dived into the pavement. Thought I lost the rear end. I tried for an hour with a 5lbs hammer and they wouldn't come out I cut them off and drilled them out then put grade 8bolts and nuts on. Then I went in the house and ordered the dpf delete.


Sent from my Autoguide iPhone app
 

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Discussion Starter #11
Come to think of it, last year we were up in the Catskills (Hunter mountain) went to a store and a guy was climbing the hill behind the store.... He was wrestling with the back half of the exaust... Thinking back, I'll bet this is what happened to him too...
if they're that weak, a good hit and snap... how did they (GM) miss this?

Sounds like I'm gonna have fun today, can't wait....
 

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The DPF flange bolts are not as bad as the DOC flange bolts. Used an acetylene torch to try and break them free and did not budge so melted the bastards right off.

Enjoy. :neener

Wait a tick, mine were replaced already by the previous owner, so if there the same as the DOC have fun.
 

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Thanks for the replies.

No Good on the DPF delete, I'm in New Yorkistan.



3 years and 38K miles, I certainly agree they're garbage, maybe the high temps corrupted them early?

So, if you couldn't hammer them out with a 5# sledge, how did you finally remove them?
Did you have to drill them out?

If I take it to the dealer, would they or have they upgraded the bolts?

I was thinking of using stainless.


Thanks again,
Rich
Yep had to drill them out. Which was also a huge pile of fun, start with a small bit and work your way up in size. I'm pretty sure the dealer will give you the same crap over again. Just go to home depot and buy some new stuff.
 

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Just get an air chisel and blast the broken ones out, They suck so bad because the "heads" have a splined section that bites into the flange and they are pressed in. Air tools will be your friend, if they arent already broken off you might as well twist the heads off em and put new ones in while your going through the exercise anyway. If they are really stuck, heat them up with a torch and stick a crayon to the joint where they go through the flange and let the wax wick into it.
 

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Discussion Starter #15 (Edited)
OK, That was fun, could have been worse...

Drilled all 3 of them out, replaced with 2" X 7/16 stainless bolts, and brass nuts (based the nuts on something I read on another site. They use them on the head, the concern seems to be that stainless nuts on stainless bolts might weld together...

anyway, they're using them on the manifold. (stainless stud, brass nuts)

We'll see how this works out.

Thanks for all the replies

Rich
 

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These bolts were a pain in the but to get out on my truck ended up having to cut them off.
 

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Stainless on stainless wouldnt be a problem, Aluminum and steel is a problem. Anytime you mix disimilar metals you have potential for galvanic corrosion. However, with a brass nut if it does stick it is very soft and a nut splitter or chisel will be able to crack it off without too much trouble. Watch those stainless bolts, I wouldnt be suprised if they rust where they are in contact with the flange. I know a stainless welding table will rust if you grind mild steel over it and dont clean it well.
 

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Happened to me too. What a pain in the ass! I came out of the house and noticed my exhaust hanging down one day. I spent an hour with a five pound hammer and punch to no avail. I ended up having to clamp it all together and bring it down to my local shop where they got the bolts out with a torch. Unfortunately they put new factory bolts back on. If (when) it happens again, I'll have to go to grade 8 bolts.
 

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Is this still an issue? Or did Chev figure this one out for the newer LMM's?
 
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