I have a fast vibration in my truck. Most noticeable at 70 mph. I changed rear-ends a while back from a 3.55 to a 4.10. This is when it got really noticeable. I have checked u-joints and carrier bearing. Just the usual pushing and pulling on them and no noticeable slop in them. It seems to go away if I slip the trans into nuetral while on highway. Also on cold start-ups while in park it seems to vibrate for 1 sec and smooth for 1 sec then vibrate for 1 sec then smooth for 1 sec. This continues until idle comes down after 1 minute. If I bring RPM's up slowly I can feel same on and off vibration. Most noticeable in dash area. When engine gets warm it does not seem to vibrate in nuetral or park. Vibration at highway speeds is always there cold or warm. Could this be a torque converter going bad? Motor mounts or trans mount? My truck is a 1993 ext cab 5.0 with E4OD. What about changing clocking position of rear end and drive shaft?? If I run it up to 75-80 mph the vibration smooths out. New tires and same vibration. Seems too fast for tires. Any thoughts from you guys?

 

I think you may be headed for new U-joints.
I had a very similar situation this week. I got under the truck and twisted the drive shaft and did my best to check the soundness of the U-joints - I couldn't get any of them to budge. I had concluded that something else was loose and it felt like it was loose close to the transmission/engine. Vibration was originally only when I let off the gas at certain speeds then started vibrating whether I was on or off the gas and got progressivly worse at almost all speeds.
I decided to stop at a transmission shop to look at the bolts on the torque converter but when they backed it up to put it in the bay, the rear U-joint let go completely and drive shaft hit the ground. Be careful and get it checked out - I'm glad it happened in a parking lot and not the highway.
Good luck.

 

Also - just to let you know how similar my condition was - my truck would smooth out at the higher speeds (68-75 mph). Upon inspection, our best guess was the the U-Joints had been somewhat neglected. They had grease fittings but I don't think they had been serviced on a regular basis and just dried out.

 

WOW - you are describing the very problem that I'm having. I have a 1993 extended cab F-150 with 146,000 miles.

I notice the vibration of the rear window and dome light - you can hear and feel it. At times, you can kinda hear a growl, especially when you go over a bump. It's easier to detect the growl at about 45 MPH, when it's quieter. Some days are worse than others for some reason.

The vibration starts around 60 MPH, peaks at 65 MPH and is totally gone at 70 MPH. It is more noticeable under load, but is still there when you take your foot off of the accelerator.

The guys I work with came to the same conclusion - U-Joints.

Good luck to us all!
Greg

 

OK,

I brought my truck in for repair based on the vibration I was having.

Rear U-joints were bad and the center bearing had some play in it.

Now it's all better - no vibration, no howl when I go over bumps or dips and it's much quieter too. It's amazing how much noise you get used when it happens gradually. After the repair the basic noise level from the drivetrain is way down - very quiet. In comparison, my truck used to sound like an old school bus, even before I had the vibartion and howling - just got used to it, I guess.

Greg

 

If the U-joints check out, it could be the torque converter. My 95 F150 did this. Are you sure you have the E4od? The presence of the OD button on the shifter stalk does not mean that you have an E4OD.
It is more likely that it is a AODE. They are infamous for TC shudder.

 

Your vibration is engine RPM dependant as you describe it. If the vibration occurs while stopped then to me that rules out the driveline after the transmission. You also stated that the vibration goes away at speed if you shift to neutral. Either the engines balance is out or something on the input of the transmisiion is out of balance or loose.
Check the obvious first such as the harmonic balancer on the front of the crankshaft for looseness or damage. Check all motor and transmission mounts as they can lose their rubber isolation and allow metal to contact metal. Check for driveline to frame/chassis contact as well as the exhaust for "grounding." Check the torque converter nuts for tightness. If all checks OK then you must isolate which component is out of balance. No easy way. You can separate the engine and transmission, remove the torque converter and fan shroud, support the rear of the engine, start it and rev it up to see if the vibration occurs. If it does than the engine is out of balance. If not more than likely it's the torque converter. At this time inspect the torque converter shell and flex plate for missing balance weights and obvious damage. Hope this helps.
Mark