Vibration When Letting Off Gas and Getting On Gas

[04DSGv6]

Just picked up an 01' True Blue Cobra the other day. It has BBK long tube headers and BBK Hi Flow H pipe. When I was driving on the highway I noticed when I press down on the gas pedal I get a vibration/sound coming from my dash area. This also happens as soon as I let off the gas. It only happens for a second or two, but the faster I'm going the worst the vibration/sound is from letting off and getting on the gas.

I'm thinking it has something to do with the exhaust and the pressure that flows through it because of the fact that it only makes this vibration/sound for a second or two when I get on or let off the gas. Like when letting off the gas the back pressure from the exhaust is causing something to vibrate real bad.

It's not noticable until I'm going about 60 MPH and from there on up the vibration/sound gets worst/louder.

If anyone has any ideas I'd appreciate it.

Thanks.

 

[Roots-type]

Check the differential mounts(bushings). The stock rubber, if that's what is still on the car, will be balooned out and throwing the pinion angle of the driveshaft off. When you hit the gas, the differential noses up. When you let off, it falls back down. These changes in pinion angle will cause serious driveline vibrations.

I doubt its exhaust related because you said it increases with speed.

 

[quick01snake]

Sounds like what mine is doing I think mine is driveshaft related.

 

[4valved]

Mine does this as well I think its my trans mount

 

[UrbanKnight]

Tighten the driveshaft where it bolts to the rear end...(4 12mm 12 point bolts) Thats what it was for one of my previous cars...

 

[Dirty "C"]

Mine has a THUMP when I put it in to first or reverse. I think it is "U" joints, any other ideas??:shrug::shrug:

 

[UrbanKnight]

Try what I said above first. 10 minute fix if that's it

 

[jacker1991]

The FTBR kit is the real fix!

Mike out!

 

[04DSGv6]

A buddy of mine also said it could be a motor mount or tranny mount, does this sound possible? The car has 85k miles. I know those mounts have never been replaced, at least from what I was told from the previous owner.

 

[TBCobra]

Another vote for drive line issue. Mine does it as well, the faster I am going the worse it is. It doesnt help I have 4.10 gears and my DS is spinning retarded fast at 80mph.

 

[kevin01cobra]

Could be motor mounts. I fixed a bad vibration that way but still have a minor vibration so I would do the easy options first with the drive shaft

 

[quick01snake]

Could be motor mounts. I fixed a bad vibration that way but still have a minor vibration so I would do the easy options first with the drive shaft

I don't think it would be motor mounts since he said it is speed dependent not rpm dependent.

 

[kevin01cobra]

I don't think it would be motor mounts since he said it is speed dependent not rpm dependent.

Motor will vibrate at some same low RPMS in every gear. In 5th the motor feels a different torque from the roads due to gearing and air resistance than it would in any other gear so it will create different vibrations. 60 MPH in 5 th for me was the start of a ridiculous vibration, same speed in 4 th created no vibration or even at the same RPM, replaced motor mounts and no more vibration.

 

[br549]

Get under the car and look around.