Help w/ High Speed Vibration

[instangator]

I have had a high speed vibration for quite some time now and I would like to solve the problem. The vibration starts at around 115-120mph, and it starts almost instantly. There is no problems up until this point then suddenly it sounds like the rear of the car is coming apart. It not only vibrates, it rattles also. I first noticed it after my gear swap, but I had never brought the car to those speeds before then so I don't know if that is the cause or not. It was never a concern before because I rarely reached those speeds, but now I am trapping 114-115mph so as soon as I cross the traps the car is vibrating. Anybody have any ideas???

 

[twogts4us]

driveshaft...get it balanced or buy an alum one - FRPP.

 

[instangator]

I thought that would be the likely fix, so I'm trying to find one now. Thanks.

 

[6Stang7]

I donno if the newer stangs are like this way, but some times how the driveshaft is oriented to the diff matters. Try flipping the shaft 180 and see if it goes away. Get this fixed ASAP though. Vibrations like this can cause major damage to you driveline.

 

[BlackGT02']

yep..aluminum Driveshaft will probably solve it buddy

 

[COramprat]

I had a nasty vibe on my car at speeds about 70-75 but it was also related to RPM's. It would start around 2500 and get gradually worse until it leveled off at 3500. Turned out I had a bad u-joint but I just put on an aluminum shaft anyway.

 

[mrpositraction]

I would try rotating your driveshaft, and simply balancing your tires. This is cheapest route first. Unbalanced tires can do this. I have had tires before that would vibrate between 50 and 60 mph only. Then go from there. I bet you would be real pissed you change your driveshaft and find out it is an unbalanced rim.

 

[propellerhead]

Read the article about driveline critical speed on www.tccoa.com.

 

[mrvax]

The aluminum d/s immediatly cured the vibration I had after swapping rear gears. Sounds like this is what you need.

 

[nickthegenius]

I have had a high speed vibration for quite some time now and I would like to solve the problem. The vibration starts at around 115-120mph, and it starts almost instantly. There is no problems up until this point then suddenly it sounds like the rear of the car is coming apart. It not only vibrates, it rattles also. I first noticed it after my gear swap, but I had never brought the car to those speeds before then so I don't know if that is the cause or not. It was never a concern before because I rarely reached those speeds, but now I am trapping 114-115mph so as soon as I cross the traps the car is vibrating. Anybody have any ideas???

Have you removed the big iron dogbone from the bottom of the rear-end?

 

[dannydoo]

why remove the dogbone?
gotta make sure the rears good,the driveline angles are correct and the u joints are good.tranny hieght is also critical,vert and horiz if you revoved the motor also.
the stocl motor mounts on my car had shims on both sides

 

[RoadconeTuning]

make sure the dogbone is there...