Horrible Vibration Issue from Driveshaft Possibly?

[ColeStang_GT]

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. Stock driveshaft.

 

[JUSTA3V]

Does the steering wheel move at all? Like side to side?

I would start simple and check to see if a tire has thrown some weights.

 

[BruceH]

I'd also start with the wheels and tires. Simple things first like lug nuts and balance. You may have broken a belt on one of your tires.

 

[ColeStang_GT]

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.

 

[skwerl]

That would probably do it.

 

[BruceH]

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.

FYI those things get torqued to something like 76 ft lbs. It's a whole lot.

 

[ColeStang_GT]

That would probably do it.

Sure would. thats the first thing I looked at to and said to myself holy f**k. That could have been bad, real bad.

 

[MADGT]

Wow, glad you got to the problem.

 

[Boaisy]

Yep, definitely thread lock it. Had a shop put blue and red loctite on my DSS because they noticed a couple bolts started to back out on one end. When we transferred the driveshaft to my friends car, we did the same, and after about a week of driving, went back and made sure they were torqued down. The good thing in my case is I had braces and loops if it ever came off. However, in your case, since it is just stock, it could've gotten nasty.