Vibration at 1100RPM+

[BLloyd]

I have a bad vibration that seems to get worse and even transmit some wobble into the steering wheel at about 40MPH. It's the worst between 38-48. It's in my D250. The front end is tight, but it feels like my left front wheel is wobbling, so I think it's the engine... ... ... ... we replaced the fan clutch which was worn, but that didn't solve much. Any ideas?

 

[pepecat]

Even though the front end is "tite" i'd still check the alignment and wheel balance.

 

[JLEONARD]

And also check the rim to see if it's bent... and make sure the chamfer on the holes is not so worn out that one of the nuts doesn't make good contact.

I've been thru both issues on mine.

 

[91W350]

Drop down a gear and drive 48, that will tell you really quickly if it is engine or chassis related. I am betting it is chassis, most likely a tire or wheel. You can also rotate the left tires and see if it moves to the seat of your pants instead. Glen

 

[BLloyd]

Drop down a gear and drive 48, that will tell you really quickly if it is engine or chassis related. I am betting it is chassis, most likely a tire or wheel. You can also rotate the left tires and see if it moves to the seat of your pants instead. Glen

I initially thought it a bent wheel, so since I was intending on replacing them, ignored it for a while. Then I replaced the stock rims with some aluminum Rickson wheels, balanced with new tires. And it's still present... ... ... . same as before.

 

[91W350]

If you drive the same speed in a lower gear and the vibration is still there, it will not be engine related, as the rpm range will be much higher or you will pass through the vibration at a lower speed if you do not care to rev your engine that high. Occasionally I drive mine where the governor catches it, just because I can. Have you checked the drive shaft as well? Glen

 

[pepecat]

bent rear axel even?

 

[dpuckett]

I went through this recently in my D350, and the following made it 80% better at all speeds except 58-61mph, and I never drive that speed anyway.



I had been having a heckuva vibration from 40mph up to about 82, but it would come and go. After 82-83, the truck smoothed out, but I could see my fuel gauge going south.



I jacked up my right front wheel, preferrably on a flat hard surface, lie concrete. I placed a cinder block in front of the wheel, and took a piece of flat steel about 12GA x 1" x 2ft, and placed it flat on the block, just barely away from the surface of the tread (1/32-1/16" clearance). Rotate the tire slowly, taking good notice of whether the tire bobbles in and out, or stays fairly even. Mine had about 3/16 runout on the right; 1/8 on the left. I marked the high spot on the tire (mine was about 120deg of rotation that was high), and then broke the tire down and rotated the high spot of the tire to the low spot of the wheel (valve stem), and runout came down to less than 1/16". Took it for a test drive, and at that time, was smooth as glass (with the exception of the 58-62ish range, had some slight vibration, that could well be the engine mounts). I have driven it a couple times since then on highway trips, and it is MUCH nicer.



If that doesnt work, check wheel bearings, as they will make a bad vibration at certain speeds, though they tend to be more consistent.



I have a thread entitled "still chasing that vibration" or something like that from a year or so ago. Lot of good suggestions in there.



Daniel