Hi everybody... well I've been going round and round with this vibration for weeks now. Its a 99 5.4l f-150 and I originally thought that it was a vehicle speed vibration, and took it to ford. The Looked through everything and found nothing. Then called me back and told me that they reproduced the same vibe while running the truck through different rpm ranges while the truck was in park. They were right. I have a low tone rumble vibration at about 1100 rpm and again at 1950-2000. It felt, and still feels like it comes from the rear, but now i know it doesn't. But the vibration is felt in the seat and armrest, not so much in the steering wheel. Any ideas you guys might have would be great. Here is the link to my previous post (when I thought it was vehicle speed related) so you can maybe pick up on some things i have left out here.
https://www.ford-trucks.com/forums/9...vibration.html
I've now realized that I thought it was vehicle speed related because at these rpms the truck is going about 30mph and 65mph respectively... guess I just wasn't paying close enough attention.
I know there are some really bright people on here with tons of experience... I hope you can get me pointed in the right direction.

 

well my moneys on the harmonic balancer...

 

another thought hopefully someone can shed some light on. im not so bright when it comes to auto trannys, but could it be something in the torque converter? my thoughts would that would make it feel like its farther back in the truck.

 

Does anyone know if these engines are slow to throw a code when there is a problem? I'm only asking because I'm thinking that maybe there is small problem with the way the engine is running. Its got a slightly rough idle, not sure if its a small misfire or something maybe with a vacuum or egr... anything like that... and when you crank the rpms to 1000, 2000, its just magnified... does that sound reasonable?
Also ran the truck up to 3000 rpm today and it has that rumble vibe again, but at a slightly higher pitch... seems its coming in 1000 rpm steps.

 

Well, I'm about to throw in the towel on this dang truck. I think i'm gonna start shopping around next week for a new vehicle. If anyone has any last minute ideas on something i can check out, please let me know. This is my first truck and I really wanted it to be a good truck... I'm just so frustrated.<!-- google_ad_section_end -->

 

I have a 1991 F250 7.3 IDI. When I purchased it 3 months ago it had no unusual noises or vibrations. When driving it home it started to make a loud buzzing sound and vibration at around 1100-1200 RPM. Typical used truck story - ran great when I bought it and fell apart on the way home. Anyways this is about my 10th used truck so I expected something to immediately go wrong after I bought it and was not surprised or dissapointed.

What I did not expect was for the problem to be nearly un-fixable. I spent countless hours reading forums to try to find the problem, and dozens of hours troubleshooting the truck to find the noise. I could not find it so I brought it to a local diesel specialist who diagnosed it for an hour, charged me 90 bucks, and told me the vibration was normal in these trucks. I then tried to fix it myself for the next week unsucessfully. Then I brought it to another reputable mechanic for a second opinion. He troubleshooted the truck for an hour and charged me 98 bucks and told me the noise was normal for a diesel truck.

Then after driving it home and almost giving up on the truck I had the idea to remove all of the fan belts and run the motor to see if the noise went away. And it did! It ran smooth as a babies, well you get the idea. I then started putting belts back on one at a time and testing for noise and narrowed it down to the A/C compressor. I removed the A/C clutch and found the pulley bearing was bad and sounded like it had sand inside of it. I replaced the bearing and it runs smooth as silk now.

Don't let anyone tell you that loud cab buzzing, noises, or steering wheel vibrations are normal in a diesel truck, they did not engineer these trucks that way or no one would have bought them from the dealer.

 

Thanks for the reply... and glad you found your problem. I unfortunately have not. I've done the belt thing and it made no difference. On the plus side, I've had the truck for almost two years, drove it about 15k and the problem hasn't gotten any worse... I guess in the end I'll just drive it until the problem makes itself more apparent... I would really just like to know for curiosity sake though....

 

Sorry I didn't read or don't remember your other post but I wonder if this couldn't be the flex plate? Sounds like something I experienced with a completely unrelated vehicle.

That time I assumed a rebuilt motor had gone south, removed the engine with flex plate and TQ still attached. After all this unnecessary work only then did I see the damage, radiating from the crankshaft mounting holes. Luckily this vehicle was already on its way to the scrap yard so it was no big deal but the lesson was some things are never as they seem.

Also just remembered a GM step van with stock steel bladed fan which had developed a crack in one of the blades. It set up a horrible vibration felt all through the truck------changing it was the cure.

Anyway a bit more inspecting seems to be in order------hope its nothing too horribly expensive!

 

The flexplate could be the issue... either a crack or threw a weight. I do have some teeth worn on it so that every once in a blue moon the starter won't engage and I get a grind on start up. but i turn the key off and it starts the next time. Its about a two inch span on the flexplate that has some wear on the teeth... could be that.