Ive had this problem for over 3 years and its only been getting worse. 97, 4.6, 103K miles. Ive had the tranny flushed 15k ago, along with general maintence. The problem is at stoplights I feel a vibration through the floor and hear a vibrating noise, If i put the pickup in neutral or park the vibration goes away. I dont have the vibration when i start moving, Hoverever, when its friggin cold like -10 and I dont let it warm up, in reverse I get the same noise/vibration. If i leave it in gear and put the park brake on and look underneath I see the exhaust virbating up and down, but not side to side. Ive noticed a rubber mount or something similiar to that which is part of a bar that acts as a brace and bolts to the exhause and sits under the tranny. If I hold or put pressure on the exhaust when its vibrating everything goes away. The problem is not a misfire or idle problem as far as I can tell, no codes come up, the dealerships are milking my pocket book for all its worth. I am curious if there are rubber motor mounts that may be getting worn out and possibly be a culprit or if anyone else has any suggestions.

Thanks

 

My '97 does the same thing. It just started it this winter. I assumed that it was the exhaust considering that the noise went away while driving and also the noise disappears after the engine warms up.

Thanks for proving it. I'm going to try the same thing on my truck and if it is; then I'll convince the wife it's time for Flowmasters.

 

At low Rpm's there will be some vibration that should be absorbed by the transmission and engine mounts. Your truck has a transmission mount by your right foot. I would check that one first.

 

On the 97s Ford put the tail pipe in front of the right rear tire.I had it moved to behind the tire and it started vibrating.I had to buy the exhaust damper and install it rite after the "Y" on the exhaust pipe. Vibration gone!

 

I've heard that some of the transmissions as they get a few miles on them, can cause some vibrations due to torque convertor slippage. My transmission shop said it is especially evident in the newer E40D transmissions. Dunno if this would be your problem, though... might be worth a check.

-Flea

 

my money is on ignition. 4.6's are a PITA for wires and wet holes. A very slight miss, will only be noticed at idle.

I'm fighting one right now. 1997 200k, I just did wires and most of the miss went away.