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Discussion Starter #1
Started tonight when I took off and started driving home. Horrible vibration, comparable to driving the car on rumble strips. The whole car shakes, feel it under the seat, shifter, all the plastic interior goes crazy, etc. Best I could isolate on the drive home was 25-30 mph, every single time in that range, no matter if accelerating, decelerating, in gear, or neutral. Seemed like it did it again also at a higher speed range but I couldn't find it on the roads to home. Will be trying to do that tomorrow.

Regardless, any ideas? The driveshaft was removed back about 2 years ago or so when I had to change my transmission and clutch. I honestly can't remember if I did in fact index the driveshaft and mark the position or not but it has been two years and it just started if that's the case. I don't think that I've ran over anything in the road to put a dent in the shaft and get it out of balance. I'll be getting under it in the morning.

It's an 08 GT with just basic bolt ons. Shifter, CAI, long tubes, o/r h pipe, etc. 60,000 miles.
 

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I'm assuming stock drive shaft? You didn't find anything loose under there?
 

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Blood, Sweat and Gears...
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Center bearing going bad?

---------- Post added at 04:26 PM ---------- Previous post was at 04:13 PM ----------

I had vibration issue for about 4 years until I picked up a old Hot Rod magazine that had an article about there 2006 Mustang that had the same problems as me. They went down the same path as me, Balanced the one piece aluminum driveshaft, adjusted the pinion angle, new tires. No help, vibration at 82 mph that was so bad that my rearview mirror had a fuzzy view, plastic dash wash going crazy.
What they found was that my drive shaft was balanced at 100 rpm. They bought a "DriveShaft Shop" drive shaft that is balanced at 6000 rpm, that was the fix.
My one piece drive shaft created harmonics at a certain rpm combined with my removal of soft bushings "shifter, LCA's, UCA", the vibration would run up and down the body of my stang.
I was so happy to get rid of my vibration after 4 years with my New driveshaft.
 

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Resident Headbanger
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Started tonight when I took off and started driving home. Horrible vibration, comparable to driving the car on rumble strips. The whole car shakes, feel it under the seat, shifter, all the plastic interior goes crazy, etc. Best I could isolate on the drive home was 25-30 mph, every single time in that range, no matter if accelerating, decelerating, in gear, or neutral. Seemed like it did it again also at a higher speed range but I couldn't find it on the roads to home.
With a vibration at such a low road speed, I'd say it's more likely there's an issue with one of your wheels. You might want to inspect the tires carefully for any bulges, uneven wear, and make sure they have equal tire pressure. If the tires are OK, have the wheels checked for balance. It's possible one of the weights could have fallen off.
 

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Go get rear tires Road Force balanced.
 

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Discussion Starter #6
Well as soon as I crawled under her immediately I looked at the problem... There was only ONE bolt holding the u-joint to the tranny flange, and it was pretty loose. The only other bolt on it was only hanging by about 3 threads. Two of the four bolts were completely missing. Guarantee that when I changed the tranny a couple years ago I didn't put threadlock on the bolts before I put them in, thats the only thing I can think of.

Didn't have much time at all today other than run to the dealer and get 4 new bolts and put them in and had to go to a dinner with family right after. Gonna be looking at a bunch of other things to make sure that the bad vibrations didn't jar anything else loose as a result.
 

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Blood, Sweat and Gears...
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Good find!
 
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