Knocking noise from backend......

[SmockDoiley]

As it says I've developed this nasty knocking noise coming from the backend somewhere. Its rhythmic and only happens upon releasing the gas pedal. It will not do it in park, and it occurs in any gear. As soon as I let off the gas it starts to do it, and immediately goes away when I gas it again. It slows down as I slow down and its not affected by braking. Car rides fine, its a 95 GT with 116k. Its an auto and the only mods are cold air, MAC dumps, and electronic shift kit which is almost always off. I did notice that when I let off the gas once the noise kicked up, then stopped as the tranny shifted, and then started again when the tranny was done shifting. Sometime this weekend, I'll lift the car up and put it in drive and see if I can get it to start again while I'm under it. Got any thoughts. I just did the shift kit and dumps and now this noise. Mufflers are tight and the noise isn't random like a shaky exhaust.

 

[SmockDoiley]

To be exact it started right after the exhaust install, and its more of a thud,thud,thud,thud than a knock.

 

[mstang2ride]

Well first thing id check is to see that the exhaust isnt close to anything that it could be hitting since it started right after your exhaust install (yes, I know its tight, but its still possible). Id also check your driveshaft, sounds like you may have a u joint going bad or loose. good luck

 

[Stang8URMPRT]

I had the same thing happen. Ended up being the passanger side muffler was hitting the driveshaft. Just check that you have ample clearance around the driveshaft/body/rear end... Also make sure everything fits tight and all the hangers are in good shape.

 

[SmockDoiley]

Like I said, I already checked all that stuff and it was good. This noise has too much of a pattern anyways.

 

[HISSIN50]

first blush i would have said rearend. but the exhaust is too coincidental. Smock, are you able to jack it up to simulate it being on flat ground? otherwise, the mufflers will hang off the underbody while the DS lowers or hangs down, when you jack it up (basically changing all the geometry).

i have had a pass side pipe hit the DS too. nice score marks on the DS.

good luck with it bud.