Thumping sound

08 gt Guy

New Member
Dec 12, 2019
1
0
0
23
Corpus Christi Texas
Everyone I’m new to this forum so let’s see how this goes I have a 2008 mustang GT when I’m picking up speed we’re going onto the freeway as soon as my car hits about above 3000 RPM I start hearing this thumping sound it’s back to back to back and it comes from the rear of the vehicle possibly the exhaust. I have long tube headers and Offroad X pipe and a straight piped rear. This problem is only started to occur recently and it seems to happen mainly whenever I first turn my car on at first I thought it was the spark plugs Because the sound is similar to whenever my spark plugs for Dad however I replace my spark plugs less than a month ago in the car doesn’t stutter whatsoever or hesitate the car has the same power and always has it’s just a weird thumping sound in the rear of the vehicle don’t know what’s causing it if it’s normal or if it’s Beth my car any info would be appreciated thank you. because the sound is similar to whenever my spark plugs were bad however I replace my spark plugs less than a month ago and the car doesn’t stutter whatsoever or hesitate the car has the same power always has it’s just a weird thumping sound in the rear of the vehicle don’t know what’s causing it if it’s normal or if it’s bad for my car any info would be appreciated thank you
 
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08GT500

Active Member
Jul 12, 2018
898
139
53
51
Massachusetts
Hi,
Have you checked for engine trouble codes, may be present without the CEL illuminated.(?)
Decipher whether it seem to be more engine rpm related or vehicle speed related? 1,001 things may cause issues as described. Narrow it down by pulling Codes & gathering information by observation. This will help find the anomaly.
Pull Codes, clean & seek out
- Engine RPM related items such as:
An intermittent COP.
A dirty MAF sensor.
A belt driven engine accessory hanging up or
out of balance.
Harmonic balancer separating.
Vacuum leak
-Raise the vehicle up using both the Jack & jack-stands for Safely by the axle to simulate ride height. Look for Chassis, Drivetrain, items such as:
Broken Coil, bad shock
Bad CV joint
Broken tranny mount.
Spin tires, check for Resistance,!tug & listen for noise, endplay.
- Tires & Rim’s, Braking or exhaust system...
Broken or missing exhaust clamp, hanger.
Exhaust flange loose, pipe striking chassis, axle.
E-brake not totally releasing; hanging up, on one
(or both) rear tires.
Tire out of balance, tire pressure(TPMS
operating, calibrated?), lost a wheelweight, rim
bent from
curb, etc.
Post what you find, k?
Good luck!
- John