QuestionQUESTION: Hi Brad, This regards my 425/409 4sp Impala.
when I pull out fairly heavy "banging" sounds, coming from left front of the car and sounds like it going through the frame, not the engine or trans. Once under way the bangs stop. This does not occur in reverse. I suspect a broken motor mount, but could not verify with the emergency brake on and slowly releasing the clutch. I would appreciate your thoughts. Thanks in advance. Ray.
ANSWER: Is this just one bang or does it appear over and over like in rhythm with a rotating part? Let me know.
Brad
---------- FOLLOW-UP ----------
QUESTION: Brad,
Thanks for your reply. it will bang a few times under load. When I back off the accelerator to shift up to the next gear it stops.Driving along its quiet. I can't say if there is rhythm as I parked the Chevy shortly after this started. By the way it started suddenly, and I do not "beat" this car. I do occasionally tickle the throttle, after all those ponys need exercise now and then. Ray.
ANSWER: I think that the 409 would get the feeling that you do not love it unless you tickled the throttle once in a while. Ok, lets start checking items once at a time. Check the tips of the fan blades to see if they have been contacting the fan shroud. If they show signs then the motor mounts are weak and need to be replaced. let me know if that is not it and we will go to the next steps.
Brad
---------- FOLLOW-UP ----------
QUESTION: Brad, the '09 is shroudless and has no fan attached to the water pump. I use a 16" elec fan attached to an aluminum 4 row radiator. Additionally "bangs" are are quite heavy in comparison to the fan blades hitting a shroud. Perhaps I should have used the term "thunk". I could almost feel them. I do find it odd that this occurs only under load, and not in reverse. A real enigma. Thanks again. Ray.
AnswerOk, lets move to the left front suspension frame area. Upper control arm bushings and mounting bolts. Rebound rubber bumpers, bent shock rod, Lower bushings mounting bolts, and cracked frame, especially in the steering box mounting area. Let me know.
Brad
