"death wobble".............chassis issue?

[Freightrain]

Ok, this is all related to my stretch job on my B model. Last year, it drove perfect with no issues.

After the stretch job, the first day out on the road, it acquired a wobble at about 55 mph. It happens with or without the trailer.

The best I can do to describe the feeling is say it's not fast(driveshaft type speed vibration), but a slower, say about 1 second interval type wobble/shake that moves the whole truck. It seems a front/back motion as best as I can tell, as the cab/bunk/steering wheel all do it in harmony. It starts about 55 mph through about 60 mph and goes away to a point. It's still there, barely, but not at the extreme it is from 55-60.

I had all rear tires off/on back after Southbend, so I know they are running true. I checked RF tire yesterday morning before heading to Wellington show. I checked the wheel bearing for tightness and also king pin. I was drawn to that corner as two different occasions after a 2 hr road trip I found my RF turn signal had fallen out of the mount in the bumper. Only thing I could figure was the shake was more concentrated there and with those snap in rubber gaskets being kinda loose it allowed it to fall out.

This thing really has me confused and at a loss as it was just so "sudden". It has new bags/shocks on the rear, but could it be a bushing that can cause this problem? I know the rear support crossmember(where bags/shocks mount) needs replaced as it's pretty beat out and the cross bar is leaning backwards. It doesn't seem driveline related, as I kept the angles the same. Same tires/rims.

Any thoughts?

[hatcity]

Possible tire/rim out of round? Balance issue?

[Freightrain]

Same tires/rims. They seem to all run true.

[macattack]

i am going thru the same thing as you. mine occurs around 35-45 mph. mine is wobble from left to right. had u joints replaced, tie rods, torque tube etc....

i am getting a trunnion rebush job done. the bushings were shot. also i am getting my front king pins replaced after my bushings are done.

one other thing you can check is your front spring hangers. when i took it in for a rebush i also noticed at that time some of my front spring hanger bolts are loose. mechanic is gonna torque everything back up after the rear trunion bushings are done.

i wll let you know how things turn out when i get my girl back.

good luck with yours.

[cgallamore]

I would bet money on a tire..

[macksmoke]

I had the same problem last week on my 1-ton dump. A belt broke in my r/f tire. You almost can't see it, it runs down the rib or tread of the tire not across. Your best bet is to fell for a high spot or jack it and spin the wheel looking at the top for a high spot!!! Good luck! Steve.

[Rob]

mechanic is gonna torque everything back up after the rear trunion bushings are done.

i

Ask him to use new hardware especially the lock nuts.

Rob

[miro]

Did you reinforce the frame between the cab and bogie?

[vision386]

Larry,just an un-educated stab in the dark,but are you SURE your stretch is true/sqauare? my dad had the frame stretched on his 85 Peterbilt,and developed much the same problem,it seems the framerails were not exactly sqaure,which allowed the differentials to be "cocked" about an 3/4 inch,and made a terrible vibration upwards of 60 MPH,the frame shop located the problem AFTER chewing up a new set of steer tires,it was such a small amount of travel,it was not noticed right off,and not thought to be the problem,but after being corrected all was well......just a thought,..........................Mark

[macattack]

Ask him to use new hardware especially the lock nuts.

Rob

i will do that.

thanks

[Superdog]

I gotta agree with checking your front tires for one being out of round or a belt breaking,just went thru the very same thing with our '01 Vision.Tire looked fine,only 16k on them.

[Freightrain]

Few years back, on my '67 F100 I had a similar problem. About 55-60 mph it would have this slight shimmy feel. Never really could figure it out, til I finally needed tires. I aired the fronts down to dismount them and the RF tire had a big sunken pocket in the edge of the tread. Hmmm, guess that was it. New tires and it drove fine.

I'm going to do a closer checkout with the front tires again. Might air them down a bit to see if they get distorted like my other tires did.

This problem has been driving me nuts and I have to go to Michigan next Saturday.

[Freightrain]

Well, just ran out and did some checking with a magnetic indicator. Seems the drivers tire has a low patch about 12" long(around) that dips .04 or so. I also checked the passenger side and Bam the same thing. Guess I need a pair of steer tires?? Ugh, there goes the g/f xmas present money LOL!!!

[hatcity]

Y'all can buy me a coffee some day

[Rob]

Well, just ran out and did some checking with a magnetic indicator. Seems the drivers tire has a low patch about 12" long(around) that dips .04 or so. I also checked the passenger side and Bam the same thing. Guess I need a pair of steer tires?? Ugh, there goes the g/f xmas present money LOL!!!

Being an understanding and compassionate woman, she'll realize the importance of new steer tires.

PS: Guard "the boys".

Rob

[Freightrain]

I do have one question. When I checked the pass. tire, I noticed the low spot was the area that was sitting on the ground. It was wet from some grass and I noticed it. The drivers side was dry and I didn't know where it was sitting originally.

Should I take it for a spin and warm them up and try again? I can't believe that new radials would flat spot like an old Firestone bias ply!!

I had the balance stuff put in the tires back when. Does that stuff go bad? Should I put it in new tires(if I Need them)?

Oh, BTW, If I were a betting man, I would say that likely she'll say that she will buy them for me. She bought my rear tires for the race car this past spring. I'm a very lucky man. The "boys" will be just fine(and in good hands LMAO).

[Rob]

Like I said, "Understanding and compassionate" I know. I've met her.

Rob

[ducky698]

Hi, hopefully its tyres, if not then does it have the same silly spring hangers at back of front springs as an R model? u know the ones with the rubber block? mine did the same thing till the front springs settled in, it kicked the hell out of the truck. I drove it in the wet an it must have helped the springs seat better in that block as its like a different truck now.

Grant

[41chevy]

Warm them up and re inspect them, cheap insurance to see if its the problem. I have never used the magic balance additive, my tire shop said it will eventually cause grief. Paul

[Freightrain]

Grant, B models have the rubber clamp in the front. Haven't poked around that part, but pretty sure it's okay.

I talked to the tire shop. They say "Counteract" is silicone based and can't harden. I told them these tires are 10 yrs old and they said they did use another product(Equal) back near that time that "could" be an issue. Only thing they can do is take the product and and spin the tires.

[41chevy]

If the tire shop has no answers, it's pretty easy to measure your wheel base. You should be able to get a reasonably accurate measurement to see if its true. Paul

[Mike]

Hi Larry........I just wanted to throw my worthless wooden nickle in about the subject. I cannot find a worthwhile reason to use any kind of liquid balance in any tire, except mybe a tractor. It seems to me that anytime you put liquid inside a tire, it will take time but will finally brake down the rubber and make it soften up where it sits for some time. And most of our hobby trucks sit more than not. Hope all is well with you.

mike

[macksmoke]

Hi Larry, do you have ribs in the front? If so check if on or two of the ribs are higher in one spot. If so you have a belt seperation.

Run your hand side to side all around the tire. If you feel that one row of rib is higher in one area (6,12,16 inch.) That's the problem.

[Freightrain]

I rotated the pass. tire to the rear and took it for a drive last night. No change, still has wobble at 55 mph. I swapped that tire back up and then rechecked runout of tires. Still has a .05 low spot on each front tire, about 12" area around circumference. I checked across the ribs, and seems pretty flat, except the outer rib is lower, but it does need a check on alignment as it's always kinda cupped the edges slightly. It's 60 yrs old, I don't expect it to be perfect.

I'm making a call today to set up an appt to have the fronts taken off and inspected for what is inside them and if that is the problem. I'm really hoping it's something simple(make that cheap), as I haven't priced new tires but I'm betting they haven't gone down in 9 yrs! I found my original receipt and it was $254 each.

My trip to Michigan this weekend is looking pale due to weather that is coming. Won't have to go if it's raining. I won't go if I don't get truck fixed.

[macksmoke]

I'm sure your sick of removing tires, but if you swap both fronts with two rears you should end up with a hop not a wobble. It sounds like you have a side to side shake in your steering wheel more than a hop through the truck. Normally if you feel it in the steering wheel it's in the front. Also a tire(s) out of balance can cause the same feeling. I may be way off here just trying to help. Feel free to call me (603)582-0252. Steve.