Slick 60's

I posted a question about front end wobble here a while back. Most comments where referring to the tires. Took the truck in had tire balance and rotated. Wobble still there. Here is maybe a BETTER explanation...

At right around 50-55mph it fells like the front end (maybe more on driver side, hard to tell) is very "evenly" bobbing up and down. If I go faster to 65 it "seems" a little better only because the bobbing in faster as well. I feel it in the steering wheel, floor, and can even see the hood moving.

The front suspension was all rebuilt a few years ago with the disc swap with VERY little miles put on since.

Truck Facts: 352/auto, has power steering and rag joint has been replaced. Has wide tires on front 255/70-15.

Any ideas?

Two questions,

Did you have the toe set on the front end? Also were the tires balanced on or off the truck? If they were balanced off the truck you might have an out of balance problem caused by wheel hub or disc rotor. Also have you had the wheels checked for a run out condition?

I have the same problem with my Suburban (yes, I know a Chevy, but you can't be perfect). Shakes at 65 exactly. Not 64, not 66... 65. At 75 it goes away a little. At 85 I come out of it. I ultimately believe the problem rests in my pitman arm or gear box. I tried to get the vehicle aligned and the guy at the shop told me there was too much play in the pitman arm to align and he couldn't do it.

What has me convinced of it is I swapped out my stock tires for some 35's I use to offroad. The shake characteristics were still there but at a different speed and at a different frequency (if that makes sense).

Toe was set when front was rebuilt. Truck does not pull and runs straight down the road.

I "assume" tires where balance on truck? Took it to "Discount Tire" chain where the wheels and tire where purchased. Told them about what I was encountering and to check everything out.

Maybe maybe not. I had a similar problem with 2 seperate cars. One turned out to be a buldge/broken cord in the tire itself the other was a bent steel wheel, it also kept throwing center caps.
.02 worth

I really don't think it's tire or wheel caused. Even if the shop did not check thing over like they said, the rotation would have changed things.

I doubt they were balanced on the truck. Getting harder and harder to find shops that still balance tires that way. Most don't even spin the tire that fast on the machine.

Have ya tried rotating the tires?

maybe try a process of elemination starting with a "known" set of tire/wheel from a different rig?......just a thought....

Check for a bad shock, a broken shock, or broken shock mount.
U@ss

Wish I had a set to pop on there. That was my thought too, but I don't.

Skip, Good idea, everything is new, but I have not specifically checked to see if a mount or shock is busted. I give it a looksie.

It's in the rotating mass... either a bad tire, bent rim, or drum out of balance. Sounds simple, but it can be a pain to figure out which one. Just be logical and try one thing at a time. The first thing is to find out which wheel and go from there.

how are the kingpins?

Ive chased this sort of stuff on multiple cars:

Rx2 I used to own, this one took awhile as it orginally had a terrible shake at 80kp/h, but tracked straight at all speeds, even when it was vibrating. Either side of 80 was ok. This was merely wheel alignment. In a fit of stupidity a year later I ran it into a gutter (ok the whole car was drifting and it was a SLAM into the gutter) buckled rim that was almost invisable to the eye, problem came back at a different speed this time. Replaced rim and problem solved.

Girfriends focus, slightly dented rim and bulged tyre from a pothole Still there ever so slightly as I never replaced the rim, but the tyre fixed 75% of it.

65 mustang, wheel balance issue. I kept getting them rebalanced to try and isolate the wheel and never realised that the weights kept throwing off until I noticed there was nothing there from the last balance!
Ended up doing an oncar balance and using stick on weight, problem solved. That was particularly annoying because it was the rear wheels so the whole floorpan would wobble.

Point of all my problems was always WHEEL/TYRE related, even with sloppy steering boxes.

As pointed out, these can be REALLY annoying to try and isolate and you're left scratching your head after lots of $$ on fixing 'could be' parts that just have zero effect on fixing the problem. I agree with the others, you might need to find someone with a set of 4 'good' wheels for you to test out. It was the only way I could get my g/f focus sorted and that was brand new from Ford!

65guy wrote: At right around 50-55mph it fells like the front end (maybe more on driver side, hard to tell) is very "evenly" bobbing up and down. If I go faster to 65 it "seems" a little better only because the bobbing in faster as well. I feel it in the steering wheel, floor, and can even see the hood moving.

One of two things is your problem, based on your description...You either have a bad tire/s (broken belt), or a bent rim/s. Tires with broken belts will still balance, as will bent rims...Spin balancers generally don't spin them fast enough to see a broken belt. As stated by another member, the problem you have is rotational.

My wife had a Silverado when we met and had the exact same issue. Found out it was pitman arms kept cracking.

Broken belt in the tire will cause a serious rumble and usually makes the truck track to one side or the other.
He says the truck is driving straight and not making noise???
U@ss

Yep, straight, no noise and no change after a rotation.

65guy wrote:Yep, straight, no noise and no change after a rotation.

Okay........Have you checked your driveline? U-joints, driveshaft, carrier bearing?

Uncle Skip wrote:Broken belt in the tire will cause a serious rumble and usually makes the truck track to one side or the other.
He says the truck is driving straight and not making noise???
U@ss

This is generally the most common issue when everything else has been eliminated. If steering and suspension check out OK and the balance of the tires is good, the problem can still be in the tire even though it balances good on the balancer.