'97 240sx base - rear end rattle/knock

[MdaddyS]

Sounds like a tin can banging on the underside of the trunk... had the exhaust guys beat on the (stock) exhaust - nothing. With the car in the air I can't find a rub point or anything loose.

This started after installing most every Cusco suspension part offered, JIC coilovers(FLTA1), ST sways front and back, Kazama subframe collars... all installed by me and double checked/retorqued by the alignment shop

Noise is worse when a passenger is in the car with me, worse on turns, seems to follow tire RPM not eng or driveshaft. If I'm very polite with the gas and driving solo I may not hear the noise. Noise is more likely to happen with a high gear/low RPM manuver (picture trying to go from a dead stop in 3rd, JUST A CLARIFING EXAMPLE, not what I'm doing )

I was leaning towards motor/transmission mounts but after driving to work without the hood today, noise does not quite correspond to engine movement. My thought is rearend now...

Hoping to provide plenty of info:I'm in San Diego.Stock eng besides aftermarket wires and K&N filter.also has SP rotors/ axxis pads/ braided lines.Enki's have been on the car for 7 years and a non factor.

Thanks in advance,Mike

EDIT: Also just replaced gear and pumpkin oil, no change in noise.also can get (I think) the same cluck to occur when dropping the clutch and pressure is off the drivetrain. I E going from fwd to reverse, backing up - up an incline. With the car on stands and my wife dumping the clutch in reverse I hear the noise but can't pinpoint it, this is what gave me the idea of motor mount because the whole eng/exhaust was jumping alot - seemed excessive... it's definately coming from rear suspension area more than transmission area.... can a bad dif clunk like this with no other dying symptoms?
Modified by MdaddyS at 12:28 PM 11/2/2005

[574-240sx]

how are the bushing in the front of the diff where it count to the subframe. I have had those wear out before and it sound like the diff it trying to junp in my back seat. Does it happen between shifts too, I would bet it the diff bushings.

[MdaddyS]

I hear a knock while shifting... I was coasting with the clutch in and quickly putting it in and out of 2nd, when hitting back in to second I thought I could heaqr the familiar cluck. That still might follow your guess.

It seems to also knock more when on the gas and turning left more so than right... would that change your guess at all?

someone is betting me a Starbucks that it's wheel bearings but I don't think that quite adds up.

Thanks for the input regardless!

Mike

[574-240sx]

I bet its the diff bushings. Check out the install pics and the ones that they are replacing with solid ones, are probably the ones that are worn.

http://splparts.com/doc/SPLSDB/default.htm