//// Truck shakes at 45 MPH ....Why ?? ////

Hi All,

I traded my pick up for a 2001 International 4700 box truck.
The truck sat for about 3 years but is in really good condition with about 225K miles and a brand new inspection.
The truck is great EXCEPT for the fact that it has a shake when you reach about 45 MPH.
Below 45 and the shake is undetectable, at 45 or so MPH it shakes very hard, about 50 MPH and up it seems to get smoother BUT you can still feel a little shake.

Looking at the tires they seem to be wearing fine (only minor irregular wear on the inside fronts) and they are only a little dry rotted (small cracks on 11 year old tires...plenty of tread tho).

Rears have only minor irregular wear.

Thinking the fronts were the cause of the problem I went to a tire shop and had the fronts reversed on the rims and balance beads added.....this did not really help the situation....

The tire shop recommended new fronts.....

I don't understand how tires (if bad balance) could only shake at around 45 MPH and then seem OK below 45 and only a little out of balance at higher speeds....We added balance beads but no real changes...

The Current tires are 295's (22.5 wheels)...

My other trucks run 11 R 22.5s

Would it be smart to go 11 R to keep all the tires the same from truck to truck or should I stick with factory sizing?

Is there an advantage of one tire size over the other ?

I am hoping new fronts take care of the problem BUT given that the old tires seem OK maybe something else is causing the shake? Any ideas on what to look for?

Thanks in advance for any and all help.

Andrew

My first thought is steering components. Ball joints, king pins, steering box. Grease everything heavy and take it for another drive.

Speed sensitive vibration makes me think driveline or tire. Take a gander and make sure all the u-joints are in phase, yokes aren’t loose, no balance weights missing. Do you feel it more in the seat or steering wheel? No bent wheels? Maybe jack it up and make sure no wheel bearings are bad, loose lugnuts etc. No mud or anything stuck inside the wheels? Broken drum?

I do know a method to isolate the issue that’s saved me a lot of farting around. It’ll tell you if it’s tire or driveline. Pull the axles, run the truck up to the various speeds it comes and goes. If it doesn’t vibrate at all after removing axles then it’s a tire/wheel end issue. If it still vibrates it’s drivetrain related. Pull the driveshaft from the diff to the first carrier bearing (assuming its long enough to have one). If it quits shaking the issue is in that shaft or the diff (less likely). If it still shakes pull the remaining shaft. If it quits then it’s more than likely that part of the driveline. If it still shakes you’re down to trans, clutch or engine vibration.

Hope that helps you narrow it down.

Check the shocks also. I change them on my 4400 just about every year.

If it sat in one place for 3 years, more than likely the tires. you mentioned dry rot... that right there says something to me. Bought a Motorhome that sat 3 years, tires looked new. It shook like crazy and blew the first tire in a quarter mile, all 6 tires were rotten where they were contacting the ground. Bought a Chevy suburban with the same scenario. I would lean toward the tires first.

Measure the tires for square. You know, corner to corner! Haha

I suggest that you get your new tyres from a dealer that has a balancer....never had any luck with beads.
When they spin the wheels they will also check for bent or out of round rims.

On second thoughts, get them to remove the beads and spin the wheels before you buy new tyres...you might get lucky.

What kind of suspension do you have? The reason for asking is I ordered and purchased a new Pete once that had 212 inch wheelbase, 18000 pound front, and Hendrickson extended leaf. It was painful to drive and empty would shake like crazy on a concrete road. I thought I had created the worlds first undrivable truck. I put the cab on air and it made the cab environment good. When I boxed it up the added weight straightened it out but it forever remained brutal as a tractor.. I concur with Junkyard check the tires for square, that is a long time to be sitting. and at one point a particular manufacturer in the early 80's seemed to be making them square

HI,

Thanks for the input thus far...

As far as where I feel the shake...It seems to me to be in the drivers seat....I don't feel any real shake coming through the steering wheel...

matter of fact , If I let the steering wheel free it tracks straight and does not shake side to side which often puzzled me if the wheels were out of balance in the front you'd think you'd feel something in the steering wheel...

The truck has been driven probably a 1000 miles by now with the tires that were on the truck when I got them.

I had a mechanic check out the steering components and it passed his inspection.

The balance beads did not seem to help... I'll see about spin balancing the tires / wheels

I'll check over the driveline....

Thanks

Feeling it in the seat and being so speed sensitive I’m leaning towards a tire. Either flat spotted a bit from sitting or maybe one is separating. Either way pulling axles will separate tire from drive line. Good luck!

Reading the posts all over again, I still lean towards driveline. Junkyard explained troubleshooting so well . The only thing I can add to that is, if you have half round yokes with straps on the u-joint, make absolutely sure those cups are not moving under the strap. Another common fault with Navistar suspension is the spring eye or torque leaf pin. Also rear shackles on steer springs. These would contribute more towards poor handling. Check your mid-ship or carrier bearing closely. A little play there can allow the slightest imbalance to get aggressive. Check your driveline angle. If the mid-ship has been replaced, there are 2 sets of holes in the cross members. Someone may have placed the hanger in the wrong holes.
Add all these options into a really long wheelbase of a box truck, you got your work cut out for you.
Good luck

Thanks for the inputs again....Ill do a more in depth look at the drive line and tires...
It's really helpful to have an idea on what to look at.