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Folks I'm really looking for some input on this... I really need to know if cars with exhaust modifications have this issue. I do know the few I have seen at show/shines & spoke with had stock exhaust & were not aware of the vibration until it was pointed out.

Again thanks for your input!


Hello all,

I’m fairly new to this forum. Have been reading posts off & on for the last couple of months & have be researching for a problem that I have experienced with my Shelby convertible.


Shelby GT500 built in later part of 2008 & is a 2009 model year.


Modifications – None, totally stock OEM equipment only.


Mileage is just under 5000 miles – car never raced or abused – basically hi way driven.


Problem: Vibration


Occurs: when vehicle moving in all gears or revving the vehicle in neutral?

Note: the vibration in neutral occurs with clutch disengaged & engaged.


Engine RPM ranges 1600 – 1700, 2100 – 2300, 3100 – 3300, 4100 – 4300 RPMS.

Note: vibration can be felt in seat, floor, doors on acceleration or deceleration when coming into these RPM ranges or revving the engine. In all gears when vehicle is moving. Less noticeable in 6th gear, but is present.


So in stating that, I hope someone can help me with this issue & has some good advice – Thanks!

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Hi GTT500 thanks for the reply. Yes car is stopped.


Check the harmonic balancer(crank pulley).Have the car running and see if you have any wobble from that pulley.And are you sure that the engine is not misfiring?You may even have a flywheel issue?

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Check the harmonic balancer(crank pulley).Have the car running and see if you have any wobble from that pulley.And are you sure that the engine is not misfiring?You may even have a flywheel issue?



The scoop – What I do know is that there is a lot more of these cars sold, worked on & driven year round south of the boarder.


1st I made a mistake converting the kilometres to miles. It has now been corrected in the original post & is under 5000 miles or 8000 kilometres.


I’ve had the car into the dealership where I purchased the car three times now.


The first time I took the car to the shop. The shop foreman could not find the complaint. (The complaint was a vibration at 1650 RPMs approximately – no other RPM range vibrations were know about at this time) so out to the shop I whet with him. We run up the car – he said he couldn’t feel it.


Then we went to two other newer 2011 units (dealer owned) the shop foreman had me run up those engines. As we neared the 1650 RPM range he told me when the vibration was coming in – proving he knew about this complaint in my opinion. The driver’s door was open & he was touching the door to feel the vibration. The shop foreman then called it a “vehicle characteristic”.


I spoke with the service manager & sales manager about that “vehicle characteristic”. In this area dealers will not let interested buyers of the Shelby test drive the car. It was determined that they would try to identify / diagnose it further.

So on my second visit, the shop foreman’s plan was to loosen of the exhaust to see if it was grounded out. Was not. Then the exhaust was unbolted from the manifolds and I was asked to come out to the shop to run up the Shelby! Well with this condition (exhaust leakage) you all know how the engine will run & hunt for RPMs.


The shop foreman’s plan was now to cut the exhaust & put flex tubes in to remedy this complaint. I spoke up to the sales & service managers about this type of repair, asking if Ford would authorize it. The dealer ship (shop foreman) ended up submitting the complaint to Fords technical support line & steering them to call it a characteristic. So they did.


I then spoke with a guy that specializes in Ford after market parts & has built several Mustangs and agreed to run the Shelby out to him to check out. He determined that the problem was a tuning issue. Meaning it could be anywhere from the air intake to the exhaust tips. He also couldn’t believe that a Ford technician wanted to cut the exhaust & put flex pipes in…One of the things this guy told me was to drive the car differently ( I was shifting the gears when the shift indicator light came on & not accelerating hard. So the engine would always come through the 1650ish RPM range where the vibration is always felt) Don’t get me wrong, I’ve had my foot into the engine compartment so to speak.


So when I left that business I started driving my Shelby. Running the RPM ranges higher & not shifting when the shift light come on. That’s when I found the vibration in the RPM ranges of 2100 – 2300, 3100 – 3300, and 4100 – 4300.


Again I went to the dealer & spoke with the service & sales managers. Also a technician because the shop foreman was not there. It was determined that the car will be booked in for another inspection/diagnostics where they would try to isolate the problem.


Upon my arrival for the third appointment the shop foreman came & spoke with me & told me the problem is related to the timing chain length. He jumped on the technician that was to try & isolate the problem – that technician didn’t spend a lot of time on the car – my opinion is he did want to step on any toes. Again the complaint was submitted to Fords technical support line & steering them to call it a characteristic. I did express my concern about the way this was handled to Ford Canada customer support & service/sales managers at the dealer ship.


Hence the reason I’m here. My apologies for making a book out of this. I’m not sure how they can call this a characteristic with out giving some indication of what is making the characteristic. I have also found this vibration in the 5.0 litre new mustang.


Thanks again for any help & advice you folks can give me! Looking forward to hearing from your large knowledge base.

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Check your plugs. You may have had some bad gas.



Hi GTT500,

Once the weather changes here I will check that harmonic balancer. we are currently at -20 *F

Car is in the garage, but garage is not heated & I don't think there is a block heater on that car - may have to wait till a Chinook blows in or spring,


Again thanks for your suggestions!

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