Turbo bark?

[Mark Rinker]

I experienced a new noise that may or may not be turbo bark while towing in the mountains with my bone stock C4500.

During high (~3200) RPM, 3rd gear uphill slogs with the exhaust brake switch in the ON position, lifting off the throttle inadvertantly engages the exhaust brake and an immediate, short vibration and loud noise is heard, during the abrupt deceleration and engine braking. Obviously, the best cure is to remember to shut off the exhaust brake when not needed, but wondering if anyone else has experienced this? Maybe the shudder is trans slippage?

It doesn't feel/sound good, whatever it is. I did this a couple of times this trip - its easy to do running heavy in lots of hills.

[DmaxMaverick]

Sounds like it is probably turbo bark (blow-back). No big deal. It could also be the exhaust brake valve fluttering from the high back pressure. No big deal, either. Turbo bark can be a problem with higher boost levels, but not what you will see with your stock LB7. In that case, or if this really bothers you, install a blow-off valve. They make more noise, but they're supposed to.

There is an upside to the bark, though. Every time it happens, it'll clean your air filter.