Vibration at idle and acceleration

[Smith1234]

I have had my mustang (94, 3.8L, manual) since Jan and had no real issues with it except a bad transmission mount that was replaced 2 days ago. After i picked up my car from the mechanic and started to drive it i noticed it sounded different under acceleration and had a bad vibration which wasn't there before. The power doesn't seem different it just feel different like something isn't right.

At idle there is no vibration until i rev it up to about 1000rpms and its starts to vibrate bad and it goes away at about 1500rpms. But its always there during driving (anytime the gas is pressed at any speed) but if i let the car coast it goes away. I am hoping someone can help point me in the right direction. Thanks

 

[Bosko5.0]

It seems that the tranny mount was replaced with a urathane mount which would create more vibration or the harmonic balancer is going bad,and needs replaced.

 

[Chythar]

Does the vibration happen when you're at a stop, in neutral? Does it happen in all gears?

 

[Smith1234]

The mount was replaced by a poly mount by Energy Suspension. The vibration happens in all gears as long as i am accelerating, if i coast i feel nothing. Even happens idling in nutral.

 

[legalize420]

The mount was replaced by a poly mount by Energy Suspension. The vibration happens in all gears as long as i am accelerating, if i coast i feel nothing. Even happens idling in nutral.

the SN body cars use a soild crossmember to attach to the body and it transfers the vibration from the engine all throught the car. on a fox body they have rubber bushings were the crossmember meets the body so they do not have this problem. replace the mount with a stock rubber piece and it will be back to normal.

 

[Chythar]

Agreed, you're getting driveline vibration. It's always been there, you're just feeling it now. The vibration isn't hurting anything, it's normal.

 

[Smith1234]

So all this new vibration which sounds like an exaust leak (during acceleration) is caused by the mount that i used as a replacement?

Also from 3rd gear to first if i am coasting for the purpose of slowing down the transmission sounds quite different. It is now a higher pitch sound. Maybe all these sounds were there before and i didn't notice them because the transmision was moving more then it should.

 

[Chythar]

Well, it's revealing vibration that was already there - the old rubber mount absorbed it instead. So technically yes - but poly mounts are stiffer than stock and thus are known to pass on vibrations. So you could say the poly mount is doing its job. Have you noticed anything GOOD since you had the mount replaced? Are shifts firmer, does the car seem to react more/better/faster?

 

[Smith1234]

Hmmmmm anything good........ the shifting may be a bit better but over all its just anoying me, to me it doesn't feel right. Maybe it will grow on me.