Truck is a 1971 F250 2wd, 390/c6, power steering, and front disc brakes. On my way to work (30 miles, highway drive) I'm experiencing a fairly bad vibration in the front end from 55-65mph but at any other speed its smooth. It's not so much a "death wobble" type feeling but more a violent vibration instead. It's just fine in town and the steering is nice and tight. All tires are fairly new and were balanced when installed. It doesnt matter if i'm turning or driving straight as an arrow it happens either way. What could be causing this? Any help would be greatly appreciated.

 

C'mon, get some skin in the game. What have YOU done already to troubleshoot your problem? Is posting on FTE your first step????

 

Probably a separated tire. New doesn't mean good-

 

Death Wobble, aka Brake Judder can be caused by warped rotors. Both Ford and Nissan have had an on-going "fix" since 2004 to replace warped rotors on their 1/2 ton trucks.

Turning warped rotors is waste of time...the "blue spots" that appear when rotors warp, 'go away' when the rotors are first turned, but reappear within a short time.

Once a rotor is warped, it is warped for life, so the only fix is a new rotor. Been there, done that with both a 2004 F150 Lariat and three Nissan Titans (2004/2005/2006).

Local Ford dealer turned the rotors on my new 2004. I told the service rep: "I'll be back in a coupla days...see you then!" Within a week I went back, the brake judder had returned, was worse than before.

Other causes of front end vibrations could be a bent frame, bent wheel(s), defective tire(s), worn front end parts, alignment issues, poorly repaired damage caused by an accident.

And btw, the vibration is there all the time, you just don't notice it until it rears its ugly head when a certain speed is reached.

Something else to consider: Do you have a two piece driveshaft? If so, you have a driveshaft center support bearing and large U shaped rubber support.

Vibrations can manifest themselves throughout the entire vehicle, so if these parts are worn, this may be the cause.

 

Thanks for all the insite guys. I am going to put the truck up on the lift when i get time on Wednesday and do a good visual inspection. I dont believe i have a two-piece driveshaft but I am not 100% certain. how can i tell if a tire has separated? will it just have visual signs of the belt separating or bulges in the tire or ??? Also the truck does get some significant bump-steer when i roll over any significant pot hole. could this mean i should replace my tie-rod ends or could this just be an alignment issue?

 

I knew there was another name for it, couldn't recall it.

Bump steer aka death wobble aka brake judder. See Post #4.

 

Like numberdummy stated check all the front end suspension parts first to make sure nothing is loose or broken. Then check you front brake rotors. My gto was awful about this same problem. I would replace the front rotors and a few months later the wobble came back. So I upgraded my rotors to some nice high dollar drilled and slotted ones and iv never felt a woble since. Good luck bud hope this helps.

 

Air down each front tire and look for sunken area in tread/sidewall.

I had this very issue with a good set of BFG Radial T/As on my '67 back a few years. It had the same basic shake at 65 mph or so, no other time. Newer tires(had them on another truck), suspension good, everything else good.

I finally wore the tires out and went to dismount them. As the one deflated, it had a sunken spot on the tread. Seems a belt separated and that was the issue. New tires and PRESTO....no vibration.

 

Well i was on my way to the shop again this morning, same interstate drive. truck still shakes in the 55-65 mph range like usual. except when i got off the interstate and onto the highway i brought my truck up to 55, 60, then finally 65 and 70. no shakes... I'm starting to lean more toward the driveshaft idea, because it only seems to shake when the truck is cruising and just rolling at 60mph and not when the drivetrain is under a load and in the act of accellerating. I'll have to pull my wheels off and check the rotors and tires as my wheels dont allow any visual of the rotor (which probably dont allow them to cool too well either). Another thought, if the rotors were warped bad enough to cause a shaking condition at speed wouldnt the truck also shimmy side to side when i get on the brakes and slow down quickly?? this doesnt happen. Do you think my wheels could be exacerbating my rotor heat issue as theyre not spoked and dont have holes to allow air to pass over the rotor?

 

Rotate your tires and see if that helps. If not then go get new rotors. Also take the truck to a alighnment shop and have them check it out.

 

I actually am taking classes at Nashville Auto Diesel College, we have several alignment racks here on campus. when i bring the truck into the shop here tomorrow evening im going to try to find an open slot to get it up on the rack. I figured that would help some of the bump-steer im experiencing. I hope my tires are alright i just bought them just a few months ago and they werent cheap.

When i start my chassis/steering/and suspension class i plan on overhauling the bottom of the trucks with all new brake rotors, shoes, pads, poly bushings, shocks, coil springs, tie rod ends, etc. but thats atleast 2 months from now

 

If its a defect in the tire and you purchased them from a reputable company ie. TireRack or DiscountTire they will replace them for free.

 

OleGreen, You guys can't bend the I-Beams can you? It'll take that to modify the caster and camber, but you could at least check it.
I'm thinking that T.A.F.A. is one of the few places in Nashville that can still do I-beam alignments. I'll be checking that out in a few months once my truck is on the road.

I'd be interested in what you come up with on caster and camber with your truck.

 

I've owned a few I-beam trucks and NONE have ever needed the beams bent. Unless someone along the way really whacked it, they should be close enough without having to bend them. Not saying it's not possible, but seems like a long stretch.

BTW, it only takes one good pothole to break a cord in a tire. You never know.

I highly doubt it's a brake thing. If you get it shaking on the highway, throw it in neutral and see if it goes away. If not, then it's likely tires/alignment. If it has too much toe in, it will cause a shake as each tire tries to steer the truck. Look closely at your tie rods, using a big bar pry on them to see if they have ANY slop up/down. Using your hand will likely not be enough to move them unless they are really bad.

 

This was going to be my next sugestion.