here it goes,

My car has had this unusuall knocking for a lil while now. At least over the last 1500 miles. Its getting to the point where it is happening less frequently but it is still there and bothering me. Its very loud and noticable when it happens and occurs on startup sometimes and when i let off gas slowing down from about 30mph or so. At least that is when i can begin to hear it. I guess you could say that sound would be as lound as someone underneath hitting something with a hammer. It sounds like it follows the rpms as to how fast the knocking is. The higher the rpms the faster the knocking and when i get all the way down to idle it just doesnt sound like its there anymore. I checked the flexplate but that seems to be alright. There was no cracks in it and no pull at all. I was thinkin about selling the car but i dont know what is wrong and am not going to sell the car in this condition. Any help would be great thanks. It is also the L03 if that makes a difference

 

If it sounds like a hammer hitting something under the car and is getting less frequent, my bet is that your flexplate has been hitting the starter gear and is gradually creating its own larger clearance.

I had a similar problem when I installed a mini-starter. A simple shim to push the starter body/gear away from the flexplate worked. It was a loud knocking noice, just like you describe (a hammer). The interference was ever so slight that you could barely see the scuffing on the starter gear. It was not readily noticable. Remember, your crankshaft has endplay.

Try this test. With the car in gear, power brake it to bring up the load a bit, but not enough to spin the tires. Have a buddy look under the car from the side and look for sparks. If he sees any, you found the problem.

Best of luck, Ed

 

im gonna go out tomorrow and check that out and see what happens. What did ya mean by shim it. I have a different starter in the shed that i could swap out if thats the problem or will i have to move something. See what happens. Thanks for the help.