Chasing a Rattle......CSX 6000

[ASO544]

I have a new CSX 6000 car with less than 700 miles on it and have been chasing a rattle /knocking since day/mile one. The rattle /knock seems to be chassis related as it only makes noise when going over bumpy areas or when the chassis flexes and it has a metal sound to it. It does it when under power or when coasting ( in gear or out of gear).

I also get a couple of popping sounds from under the car when I push the car out of the garage ..... which I usually do to keep from killing the family with the exhaust : )

I got under the car and checked the usual suspects

1. Drive shaft is tight with no play
2. Rear end seems tight
3. Tranny is mounted tight
4. Side pipes are tight
5. Parking brake cables are zip tied to minimize movement
6. Wheels are tight
7. Battery behind passenger seat is mounted tight
8. Seat belts where they attach to the body are tight
9. Trunk lid is tight and I removed the trunk lift rod just to see if it was the culprit and it wasn't.
10. Rollbar is tight
11. Electric fuel pumps a tightly mounted
12. Seats are tight and no movement.
13. Gas cap is tight
14. Tail lights are tight
15. Tags mount is tight
16. Jack lifts are tight
17. Aluminum wheel well close out panels are secure.

The one thing that has me concerned is the rear end was replaced under warranty during the power train install as it had a loud howl. Im wondering if something wasn't secured properly on the install but everything looks and feels tight and there is no tell tell "thunk" you usually get with a loose pumpkin. Car drives great.

My other concern is I can only check the car when on jack stands and the suspension is full flexed so that may be hiding the problem.


My next move will be to remove the rear tires and check the rotors and calipers just to cover that possibility but feel they are good based on how the car drives and stops..

My other thought is the fuel tank. Maybe it's loose inside the rear housing as I not sure what actually secure it to the chassis. I also noticed the two large bolts that you can access from the access plates in the trunk....are those for the rear end mounting?


Any thoughts or suggestions will be greatly appreciated? I'm sure it's gotta be some thing simple and staring me in the face.

[EM-0785]

ASO544,

Just a thought regarding your comment: "My other concern is I can only check the car when on jack stands and the suspension is full flexed so that may be hiding the problem."

Whether for this issue or future reference, a set or two of RhinoRamps or similar from the parts store can supplement the jack stands with a similar height while keeping the suspension engaged when needed. I went with the heavier duty ones, not for the extra weight bearing capacity, but they're wider to better handle wider tires.

You can check/access engaged suspension with wheels turned at various degrees for clearancing, brake line routing/testing, etc. as well.

Good luck finding your noise issue. Brent

[mrmustang]

Check pinion angle, check driveshaft U joints for binding........Both will need to be done on a drive on, four post lift so that suspension is still compressed as if the car was on the road.






Bill S.

[cobrakiwi]

Check the aluminum panels, the rear bulkhead and the inner rear splash panels around the fuel tank.

Also check the clutch fork, depending on what setup you have (external slave with fork) the fork can rattle against the main frame rail if not setup correctly.

[1795]

Originally Posted by ASO544

I also noticed the two large bolts that you can access from the access plates in the trunk....are those for the rear end mounting?
.

Those two large bolts are for mounting the differential.

I would agree with the others that you should get the car up n ramp t keep the suspension compressed and check the angle between the tail housing of the transmission and the pinion of the differential.

The problem with getting the car up on a lift so that the suspension is loaded is that you cannot turn the tires and see the driveshaft moving and listen for noises. I was just thinking that maybe if the car was on a dyno you might be able to run it at ow rpms and listen for a noise and possible look for things that may be binding or moving?

Let us know what you find, and good luck.

[MOTORHEAD]

I have a similar knock going over bumps. Early Kirkham, original style suspension, bottom shock mount has rubber bushing, not enough clearance when suspension movement causes bushing to compress. Note wear points where shock tab has been hitting a arm and mounting tabs.

[ASO544]

Thanks for the start guys.

[Tjd]

Jack up one wheel at a time with the jack under a arm so the wheel off the ground and then turn and shake the wheel to see if there's any play we careful it doesn't fall on you
Do both rear wheels at the same time if you have two jacks or block one side up and hold the other room with the Jack then rotate wheels and listen for noises
Only have to lift it high enough so the wheels not touching the ground
Tom

[jhv48]

Four of the popping sounds could be from the springs re settling on their perch. Every time you raise the car, the springs hang loose and when you lower the car, it can take a few bumps for all four of them to reseat.

[Kit Coyle]

I think these are are reasonable suggestions to check into. Haven't you
checked with the Shelby people? This is a low mile CSX car, fairly new,
and a "premium" was paid for it. What do they say? If the car was an ERA
you would get helpful answers by just picking up the phone and calling
them.

[RodKnock]

Originally Posted by cobrakiwi

Check the aluminum panels, the rear bulkhead and the inner rear splash panels around the fuel tank.

The rear bulkhead was the one rattle that I found quickly and easily. While driving I just put my hand on it and the rattle went away. Ultimately I installed carpet in the trunk and the noise disappeared.

[E5USMC]

Try the drive shaft hoop