Help Diagnosing a Hard Contact Point/Noise


New Member
Mar 9, 2023
Thanks for reading, everyone. I need some help troubleshooting a hard contact "bang" noise when my 87 GN goes through a steep dip (for example a transition joint on the highway between bridge and pavement). It only happens when the car has 2 or more people. The noise sounds like it's metal on metal, and seems to be coming from the passenger side under the front floor mat. Some say its coming from right behind the passenger seat, it's really hard to tell due to sound travel. The passenger can even feel the contact vibration when it occurs.

Just three weeks ago I had the front end suspension rebuilt.
- new inner and outer tie rods
- new center link
- idler arm and brackets
- QA1 front duel adjustable coil overs and springs
- QA1 thrust berings

This helped quite a bit and the contact happens less but it hasn't eliminated the issue completely.

Are there any specific points I need to check for contact? Any other ideas of what this could be? As always, I really appreciate the help, input and time, and feel free to ask me any questions. Y'all be safe out there.
Have you checked the exhaust hangar/bracket?

Could be the converter/exhaust moving if the rubber has broken or if the converter/exhaust is too close to the floorpan. Take a look at the heat shield as well.
Check to see if the downpipe is making contact with the upper A-arm mounting points . Mine has a slight dent from suspension contact .
Thank you guys, really appreciate the feedback. I'll be checking these points this evening after work and will report back.
When the installed did they install the QA1 thrustbearing kit? Highly recommended.

Did they install new coil spring isolators?
This I think is more likely your issue.
Also check upper pass a arm hitting down pipe
Driveshaft loop? I had to take my aftermarket one out. Its the weird angle looking one. I have an hr trans mount and with two or more people in car the driveshaft hits it.
Appreciate all the feedback guys.
Checked the exhaust hanger and it's in great shape.
Sorry guys, accidentally hit post while writing.

Appreciate all the feedback guys.

I didn't see any evidence of contact between the downpipe and a arm. Checked the exhaust bracket and its in really great shape. But, while under the car I found what could be a contact point from an exhaust pipe and the undercarriage (picture for reference). Ironically it is slightly behind the passenger seat, which is where some say the noise is coming from. The exhaust does have play in it and very little clearance at this point with the car parked. I'm going to mark it up with chalk, load up the car, and do a test run on Saturday. Fingers crossed we found it.

@AN/GNC-52 they did not install the thrustbearing kit or iso's, and I'll certainly do some research on these.


  • 20240308_033435.jpg
    2.3 MB · Views: 20
For the isolators I like the OPGI ones better that MOOG.
The thurst bearing kit is highly recommended by QA1. Seems like it would make adjustments easier by preventing the spring from binding.