6 speed barking sound after hard acceleration

[PBerry]

I just developed a bark/chirp/screech sound after letting off of throttle after hard acceration. It will do it with stock fueling in 6th gear. There has always been a quieter version since new when letting off of throttle suddenly in 6th gear. I do not know why the truck does it, so I am looking for some leads from someone who knows more than me.

 

[rbattelle]

I believe what you're hearing is turbo bark. This occurs when the sudden drop in energy available to the turbine results in reverse flow through the compressor. When you suddenly drop the throttle the manifold pressure is very high but you've lost all your exhaust energy so the compressor can no longer continue to drive flow. The resultant condition can be severe enough to snap the turbo shaft and should be avoided at all costs.



-Ryan

 

[sag2]

I was researching turbo bark and found TSB 11-05-96 that says the turbo will bark (actually described as woof woof woof) when going to sharp decel, and it is completely normal. Nothing has really changed from then to now as far as basic plumbing and design. I just could not imagine that virtually all trucks do it under the right circumstances, and it would cause a turbo to fail. Looks like this confirms it is normal.