One thing leeds to another.

[Bob Dunahugh]

I brought up the heatshields. That got me looking more closely at the exhaust system. Pipes are fairly good. BUT. Who ever replaced the system. They didn't put the 3" sleeves in the muffler bearings. ( And for those new owners. Our GMC's really do have muffler bearings. Really. ) So now I'm replacing the exhaust system. I've always seen the bearing sleeve welded to the tail pipe. Is that what GM did? Someone told me that GM used self drilling screws. I don't think that's the case. Bob Dunahugh

 

[powwerjon]

Bob,
The muffler bearings are for a 3” pipe. The 2.5 in had a 3” sleeve welded to the pipe.

http://www.appliedgmc.com/prod.itml/icOid/1180

http://www.gmcmhphotos.com/photos/general-pictures/p64945-3-26quot-3b-sleve.html
http://www.gmcmhphotos.com/photos/general-pictures/p64946-3-26quot-3b-sleve.html
http://www.gmcmhphotos.com/photos/general-pictures/p64945-3-26quot-3b-sleve.html

J.R. Wright
GMC Great Laker MHC
GMCGL Tech Editor
GMC Eastern States Charter Member
GMCMI
78 GMC Buskirk 30’ Stretch
75 GMC Avion (Under Reconstruction)
Michigan

>
> I brought up the heatshields. That got me looking more closely at the exhaust system. Pipes are fairly good. BUT. Who ever replaced the system. They didn't put the 3" sleeves in the muffler bearings. ( And for those new owners. Our GMC's really do have muffler bearings. Really. ) So now I'm replacing the exhaust system. I've always seen the bearing sleeve welded to the tail pipe. Is that what GM did? Someone told me that GM used self drilling screws. I don't think that's the case. Bob Dunahugh
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[Matt Colie]

Bob,

There is no way I would use self drilling screws there and I am sure that GM would not have done so either. It would be warranty in waiting.

Mine had been replaced and the installer just hammered the 3" down close enough to make an easy weld to the 2-1/2.

I cut the 3" to have four long ears on each end and used a muffler U-bold to make them up to the 2-1/2. It has only been a year so I cannot say how
good a fix this was.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit

 

[johnny]

When I had the local guy do the ratrod exhaust, he took a piece of 2 1/2" pipe and expanded one end on his Muffler Person' machine till the 3' was a
snug fit, and then MIG welded all the joints. Doesn't leak and doesn't rattle.

-johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased