Whats my most likely vibration cause?

My 07 Gt500 has been on the back burner for a while but now that I have a few projects finished up I want to start using it again. I had gotten some new wheels and tires a while back along with upgrading my driveshaft and somewhere around that time I developed a vibration at higher speed around 100 MPH or faster. It hasn't been a big deal because I don't spend a lot of time driving that fast but as many know the cars can get there in a hurry if you want to have a little fun. My wheels are American Muscle 2010 style Gt500 wheels, My tires are Michelin Pilot Super Sports, and my drive shaft is a Drive Shaft Shop one piece aluminum shaft. Other mods in sig. Any ideas?

Thanks
Greg

Was the driveshaft balanced?

Have weights on it?

Did shaft come complete ready to bolt in or did you have to add your slipyoke and rear flange. Where if you had to add your parts it still needs balancing before installing

I have a similar setup to yours, minus the AM wheels. Check your pinion angle with your suspension loaded... -2.0* is your target value. If your driveshaft is new, it is unlikely that it is causing the vibration because DSS does verify that each shaft is high speed balanced. However, the aluminum one-piece design is less forgiving than the OEM steel two-piece shaft (less dampening), so it will transmit more NVH from other driveline components; having swapped mine out a couple of times, I can attest to it.

Check that your brake rotor retainer clips are/were removed. They may interfere with flush mounting on some aftermarket wheels.

Next, I would have the wheels and tires road force balanced from a reputable establishment. I took mine to my local Ford Dealer and the machine cut the actual weight required for each tire from a solid thin lead strip, making installation cleaner looking and less chance of throwing weights at high speed.

Third, I would disconnect the driveshaft from the rear pinion flange, rotate the driveshaft 180*, re-connect it and re-torque bolts.

Lastly, I would replace your new wheels and tires with your original ones, if you still have them, or borrow a known good set from a buddy to rule out wheels and tires as the culprit.

SCGallo2 said:

Lastly, I would replace your new wheels and tires with your original ones, if you still have them, or borrow a known good set from a buddy to rule out wheels and tires as the culprit.

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Ditto, with the driveshaft. Did the vibration happen when you made one or more of these changes or sometime thereafter. If so, how long? When I've had driveshaft problems they generally start at lower speeds and get progressively worse the faster you go.

Is there any way to put your old wheels and tires back on. You could eliminate one at a time until you find the issue.

oldstv said:

Is there any way to put your old wheels and tires back on. You could eliminate one at a time until you find the issue.

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this. I had MPSS tires, and that was the issue. Sadly it as expensive. There have been issues in the past with the MPSS.

I would start with the simplest and easiest.... get the tires and wheels checked carefully and balanced precisely. I go through this kind of stuff all the time, and when I go to the tire shop, I am ALWAYS sure to grease the techs' palm with some cash, usually a $20 bill, that way I get treated like a king, haha! Explain to the tech what is going on and let him check everything out.

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Get away from the NTB's and Discount Tires of the world for balancing and get to a specialty shop. Every decent size town has one or more of these shops, and they don't charge much more for balancing. Local forums and other info sources should be able to direct you to the good shops.

fullboogie said:

Get away from the NTB's and Discount Tires of the world for balancing and get to a specialty shop. Every decent size town has one or more of these shops, and they don't charge much more for balancing. Local forums and other info sources should be able to direct you to the good shops.

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It all depends on the techs IMHO. I use a local Town Fair Tire, which is a chain. They have the latest and greatest equipment, and the guys there have been stellar, especially with a little gratis thrown their way, haha! You gotta get to know the techs and manager and build a little rapport, let them know you're a 'special' customer, that's the secret IMO. Those guys all LOVE high performance cars like ours, so they are more than willing to go the extra mile.

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Thanks for all the replies. I probably made a couple too many changes at once on the car but some were needed and so it's a little hard to point a finger. Also I haven't had a vibration come in at a higher speed before. You can cruise the thing at 90 mph down the highway and it's smooth but when I make a quick pull and get to 100 or better is shows up. Wheels were bought new from American Muscle. One of the fronts came bent and was rejected by the tire shop but AM replaced it with a new one. I bought the Michelins through Costco since they had the best pricing and I had them mount and balance everything. Unfortunately I sold the stock wheels to fund the new ones and I don't have those to try anymore. I may be ably to borrow a friend or family members.

These were installed 4-5 years ago and I believe the vibration has been present from the beginning. Unfortunately right after installation My 70 Mach 1 was rear-ended in a collision and that sparked a 4 year full rebuild on that car along with two baby boys and a move to a new house so the Shelby hasn't gotten a lot of attention since that time. With the other projects getting finished and life settling down I think it's time to get the Shelby sorted out and get back to driving it!

builttodrive said:

Unfortunately I sold the stock wheels to fund the new ones and I don't have those to try anymore. I may be ably to borrow a friend or family members.

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You may want to try swapping the tires back to front and see if the vibration changes. If the vibration was in your butt and then changes to the steering wheel its probably the wheels/tires. If it stays in your butt then it could be the driveshaft or pinion angle.

Here an extract from this page that may help: The Driveshaft Shop | Driveshafts 101

DRIVESHAFT VIBRATION: 101 (not for CV axles)

Most people have trouble determining if the vibration in their vehicle is coming from the DRIVESHAFT or not. There are typically two types of vibration most vehicles would have. A fast cycle vibration or a slow cycle vibration, to help understand this lets say we put a bucket of water on the passenger’s floor. If the vibration in the vehicle produces small ripples on the top of the water this would be considered a fast cycle vibration. This type of vibration is usually a drive train vibration, things like the driveshaft, motor or torque converter. If the vibration puts waves on the top of the water or splashes, this type of vibration is a slow cycle vibration and usually is an axle or tire vibration. People have trouble determining where the vibration in their vehicle is coming from. Try the test below if your not sure.

JACK TEST

A simple way to do this is out the vehicle in question up on jack stands (make sure the vehicle is completely secure), block the front tires and run the vehicle up to the speed you have the vibration. Make sure you use the brake to stop the drive train before you put the car in park if it’s an automatic. If the vibration is a fast cycle vibration you may want to have the DRIVESHAFT checked for balance. This may make no sense to you but you may try indexing the shaft 180 degrees (just pull the shaft off the rear yoke and put it on the opposite way). What this does is change the resonant frequency property of the driveline and in many cases it takes the vibration away. If you have a slow cycle vibration take the tires off the car (make sure you put lugs back on the axle to keep the brake in line) and run the vehicle again. If the vibration is gone you now have to find out if it’s the rim or the tire and good tire shop can help you with that. This is a simple test for any vehicle but please if you’re not completely sure of how to put the car on stands safely bring the car to a certified technician to perform the test. If you want further help with understanding this process or want help understanding vibration problems please call or e-mail us. We live for drive train and will help as much as we can.

Hopefully I'll be able to dig a little deeper and investigate along with road test the car again soon but I am wondering how recently TDSS has updated their shaft. I purchased mine from Van at Revan Racing in May of 2015 and I noticed on the website they talk about a new and improved design.