U-joint going bad, or something worse?
08-30-2011, 09:48 AM
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U-joint going bad, or something worse? Quick backstory, car is an '02 Z28 M6, 76k on drivetrain and chassis, 4.10 gear, mild cam, street tires, I drive it daily to work and school, never been to the track since I've owned it. I haven't launched it from a stop, only get on it when nobody is around or I'm getting on the interstate or something.
I drove to work just fine yesterday morning, but driving to school after work I was noticing what sounded like an exhaust leak at the time, and didn't think much else of it. On the way back from class, the noise became much louder and I started picking up a knocking vibration in the shifter a little. At first I was thinking engine, but when I disengage the clutch and free rev the engine it sounds perfectly healthy and normal. I had the car in sixth, and when I'm off the gas and letting the car coast in gear it doesn't make any strange noises. It's only when the car is in gear and I'm accelerating it begins to knock and vibrate a little in the shifter. At low speed in 1st/2nd/3rd it doesn't really make the sound, but once I get up to maybe 50-60 it starts and gets much louder as speed increases, so it seems speed dependent and not so much rpm dependent. I'm hoping it's just a u-joint maybe has gone bad and not something really serious like the rear end making it's death rattle.
Anyone had a similar experience or maybe take a wild guess at what this could be?
I drove to work just fine yesterday morning, but driving to school after work I was noticing what sounded like an exhaust leak at the time, and didn't think much else of it. On the way back from class, the noise became much louder and I started picking up a knocking vibration in the shifter a little. At first I was thinking engine, but when I disengage the clutch and free rev the engine it sounds perfectly healthy and normal. I had the car in sixth, and when I'm off the gas and letting the car coast in gear it doesn't make any strange noises. It's only when the car is in gear and I'm accelerating it begins to knock and vibrate a little in the shifter. At low speed in 1st/2nd/3rd it doesn't really make the sound, but once I get up to maybe 50-60 it starts and gets much louder as speed increases, so it seems speed dependent and not so much rpm dependent. I'm hoping it's just a u-joint maybe has gone bad and not something really serious like the rear end making it's death rattle.
Anyone had a similar experience or maybe take a wild guess at what this could be?
09-10-2011, 09:36 PM
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Even with so low miles? I'm sure it's always possible just to have something like that go bad early, but I haven't been to hard on the trans with powershifts or anything.
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09-24-2011, 02:11 PM
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Bump, I finally had a chance to get under the car today. I can't visually see anything wrong with the t/a mount, or the trans mount. I did notice about midway on the ds it looks like something rubbed a small groove in it, which makes me think back to a u-joint going bad and allowing the ds to move around and hit something. How can I determine if one of the u-joint has gone bad, what are the signs?
09-25-2011, 06:01 PM
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If its a bad u joint can check it by wiggling the drive shaft with your hand and see if it has a lot of play in it. MAKE SURE the E brake is on and the car in neutral. But with the miles you have and the way you say u drive, i doubt a U joint is the case. 
09-26-2011, 11:27 PM
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U joints are cheap, replace them. However, stock DSs with rings rubbed into them are not safe. They are literally as thin as a coke can to start with. I'd purchase a new/used DS if it was me.
