79 4X4 F-250 400M C6. All stock. There....now that all that's out of the way, I have been noticing a very fast vibration when I run on the higway over 55 MPH. Hubs are unlocked, X-fer case is in 2H. I always thought U-joints made niose when they're going out, but all is quiet. Is there anything other than the driveshaft U-joints that could cause this? Front axle U-jounts and tie rod ends are new. No noticable slop in the wheels or steering.

 

Check your rims and tires for balance, mud packed in the rims, broken or shifted belt in a tire, etc.

 

could still be a u joint, they dont always make noise when they cause vibration. otherwise probably a tire balance issue like chrepy said.

 

Speed related vibrations are very often tire and wheel balance, as these two have mentioned.

Also, it's 351M, and 400. No need for a letter behind the 400.

 

if your on a concrete highway then it could be the expansion joints and should go away at about 70mph

 

i have a vibration aswell after 55 up to around 65 then it comes back right at 75 and wont go away until i hit about 80+ish

 

I had the same problem once. I had a U joint that went bad and I didn't change it soon enough. It caused the holes in the front driveshaft yoke to wear.

When I replaced the U joint I noticed that the cups didn't fit the yoke very tight, but since I was twenty miles from home, I put it in anyway and drove it home. I felt a slight vibration in the steering wheel and on the floor board.

At first I thought it was my imagination because on some days it would vibrate and other days it wouldn't. Once I changed out the yoke, the vibration went away.

 

What about the slip joint in the drive shaft, it it's going you'll get that vibration, i have that and it's the slip joint going bad

 

I had that same vibration symptoms on my '79 F-350 4x4. I found out what it was when I stomped on the gas at 65 mph. I heard a loud bang and then heard my driveline bouncing on the freeway. I'm lucky it didn't roll my truck. The front part of the driveshaft was gone. All that was left was a tube bolted up to my rear.

 

currently have a similar vibration but it is slight...right front and all ujoints have been replaced- was fine before that.

 

VLS

After you drive the truck, crawl under it and feel your u-joints. If they're hot, they're shot.

 

Great topic VLS I have the same problem on a 73 2 wheel drive. I replaced springs and shocks front and rear, king pins new tires and rims. Truck is a three speed replaced clutch pressure plate and throw out bearing. Looks like I will be replacing u-joints.

Thanks guys

Keith

 

You guys are sick driving a 4x4over 65.That's alot of weight to stop fast

 

Check tire balance, front end alignment, steering ball joints, U-joints, carrier bearing, lug nuts, shock-dampener on the front end steering. King pins if you have em, Shocks, drive shaft slip joint. Got to be one of em

 

It’s a feel thing.

It’s been my experience that worn steering components wont cause a vibration but will amplify one.

A rear yoke or u-joint going bad will cause vibration, sometimes intermittent, sometimes consistent and sometimes at various speeds and loads (depending on the ware and what’s worn). It’s very rapid, you will feel in your feet, through your seat, or both.

An unbalanced tire will cause a much slower vibration. If it’s a front tire you will feel it at the wheel and/or threw the floor, if it’s in the rear again you will feel it in the seat.

There are many components in a driveline and any one of them can cause a vibration. To check, with the E brake off, the trans in natural and both rear wheels off the ground, grab the drive line at the rear and wiggle looking for any movement including slip joint, u-joint and the input shaft to the rear end (both up and down and in and out). Now spin the DL feeling, looking and listening for anything unusual. Pay special attention to the rubber seals next to the cups looking for any signs of rust. Follow the same procedure for the front, include checking the shaft out of the transfer case.
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If the DL system is the source of the vibration you should find it is using this simple method. Some say a balance weight could come off, however I have never had it happen to me. If it is the DL and this procedure doesn’t locate the problem you might have to R&R with a trip to the shop for a check up and balance.

I recently had a DL vibration and found my transfer case exit shaft to be the problem. After some tough use and 500,000 miles its time for a TC rebuild.

What ever you find, please let us know. Thats the fun.

Craig....OUT