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Shaky 4.3 GMC

I have a 4.3 liter engine in a 2007 GMC that shakes at 1250 RPM. The dealer hung weights on the exhaust cut the exhaust in two and put in a section of flex pipe and replaced the drive shaft. They then told me "They all do that " we have been in court for over two years and the truck has a total of 820 miles. has anyone else had this issue?

Any “Check Engine” Illuminations? Are They Retrieving Any Fault Codes?

I’m just throwing out guesses here. There are TSBs on some 4.3s for clogged injectors and “rough idle, surge or chuggle, and light or intermittent misfire, check engine light”, etcetera.

What about the harmonic balancer? Torque converter/flex plate?

P.S. Mechanics re-engineering your 2007 truck doesn’t sound like the hot set-up. They are trying, but could create more problems than they are solving. They need to zero in on the correct diagnosis and not re-engineer. I would have a hard time believing that these truck “all do that” and it wasn’t caught before going into production. Your’s has done this from day one?

NO Check engine nothing . This is an Harmonic vibration . I took it to an engineering firm and had accelerometers mount in several places on the truck and graphed the vibration.

Excellent job of locating the fault. Pretty high tech solution.

If I were you I’d go back to the GM dealer and tell them to replace the exhaust they cut up for no reason other than WAGs.

That flex pipe will rot out in no time, especially if you’re driving in a road salt zone.

The last time we went to court I was ordered to take it back to the dealer for one more inspection. The truck does not start because the battery has gone bad but the dealer would not replace it because the court case has not been settled. fat chance of getting them to fix the things that they have messed up.