On occasion I will get a really hard BANG sound from the back of the car. I can't duplicate it on purpose, but it seems to happen when getting hard on the gas, while turning left, over areas where the rear suspension partially unloads or loses grip, and then regains it.
Basically the only time I've heard it is
1. during rallycrosses at various spots here and there.
2. on a U-turn that I make occasionally where the right side wheels go off into the dirt on the shoulder, and the bang happens as they come back onto the pavement I think.
3. the other day, while turning left into my driveway (which has a dip at the transition where the right rear wheel may lift off the ground).
The sound is best described as if someone has a hammer and whacks the bottom of the car really hard, somewhere around the fuel tank, back seat, or forward area of the trunk.
A few notes:
1. shock mounts are good, new, and have reinforcement plates.
2. diff bushing is new
3. subframe bushings are new (both the main bushings and the trailing arm bushings)
4. all suspension parts and subframe bolts are torqued to spec.
The only things I can think of are:
1. Some kind of swaybar bind (though I can't see how that could happen with this design....stock 325 sway with stock endlinks, also new). Though I guess I'll check the swaybar mounts in case something broke.
2. something loose on the diff mount (I haven't checked the bolts that secure it to the chassis, but will this weekend)
3. something internal in the diff (it's a 3.91 LSD, but works fine)
4. ???
Thoughts are welcome. This is the rallycross car, so I'm not generally concerned with noises, but these bangs are with such hard force it seems something that could be an issue.
Also saw someplace someone said something about the diff mount flexing the trunk floor "like a paint can lid" which could cause such a bang. Any experience with that happening?
Thx
Josh
Basically the only time I've heard it is
1. during rallycrosses at various spots here and there.
2. on a U-turn that I make occasionally where the right side wheels go off into the dirt on the shoulder, and the bang happens as they come back onto the pavement I think.
3. the other day, while turning left into my driveway (which has a dip at the transition where the right rear wheel may lift off the ground).
The sound is best described as if someone has a hammer and whacks the bottom of the car really hard, somewhere around the fuel tank, back seat, or forward area of the trunk.
A few notes:
1. shock mounts are good, new, and have reinforcement plates.
2. diff bushing is new
3. subframe bushings are new (both the main bushings and the trailing arm bushings)
4. all suspension parts and subframe bolts are torqued to spec.
The only things I can think of are:
1. Some kind of swaybar bind (though I can't see how that could happen with this design....stock 325 sway with stock endlinks, also new). Though I guess I'll check the swaybar mounts in case something broke.
2. something loose on the diff mount (I haven't checked the bolts that secure it to the chassis, but will this weekend)
3. something internal in the diff (it's a 3.91 LSD, but works fine)
4. ???
Thoughts are welcome. This is the rallycross car, so I'm not generally concerned with noises, but these bangs are with such hard force it seems something that could be an issue.
Also saw someplace someone said something about the diff mount flexing the trunk floor "like a paint can lid" which could cause such a bang. Any experience with that happening?
Thx
Josh
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