gtodoug

iTrader: (1)

I just had the 3.91 gears installed and the car drives fine in a straight line. I though from time to time I was hearing tan thump, thump noise on take off but not positive. Even in the slightest turn the car is making a thump.............thump.............thump sound. It's almost as if something is stuck to the tire but you can tell the sound is internal. I talked to the tech and the only thing we can come up with is that since we put the harrop diff cover on it holds like double the amount of gear oil. He had only put the recommended amount of friction modifier in for the stock cover, but ended up putting almost double the amount of gear oil. The second thing is we used Mobil synthetic gear oil instead of the gm stuff. Same weight as the gm stuff though. Any negative effects from using the synthetic stuff with the friction modifier from gm? He thinks that since there isn't enough friction modifier that because of the amount the new diff cover holds it's being "watered down" and not allowing the diff to get enough lubrication causing clutch chatter in the diff. I hope I said all that right. Anway I need some opinions.

We ordered the gm fluid and are going to drain the mobil and add the correct amount of friction modifier with the gm fluid. Anybody think it might be something else?