The Stovebolt Site Forums The Shop Area Driveline shaking front wheels

i have a 1939 chevy 1.5 ton truck , i had the front straight axle rebuilt a couple years ago , new king pins , wheel bareings, updated 20 inch steel wheels and tires with balancing , new tire rod ends , rebuilt steering box , font shocks .
cruising around 40 to 45 miles per hour the front wheels start to shake real bad , when i raise the front end to check the wheels for any free lay , they feel very little play vertically , no play horizonely , what am i missing ?

Should your truck have caster shims on the front axle? Does it?

Sounds like a balance problem or out of round tire. You can check the balance on these big wheels by raising the front end & backing off the brakes so the wheels turn freely. Then turn the wheel slowly to see if it will rock back & forth. If it does you can place weights on the opposite side of the heavy side of the wheel. Place a jack stand or block of wood close to the tire & rotate the wheel to see if it is out of round or has lumps on the tire.

George

Look at the wheels to see if you see any places where the weights fell off.

Swap front and rear tires on one side and see if there's any change. If no change, do the same on the other side. If there is a change, you'll know that the tire you moved to the back is the culprit. You may even have a belt separating inside a tire. I've had that happen on tires with under 10k miles on them.

Make sure all you lug nuts are tight before doing anything. I know it sounds silly but you never know if the guys that installed the new rims tightened them down correctly or not.

I've seen caster angle problems plus incorrect toe-in cause this (along with wheel balance, tires not true, tire belt separation, tires worn in a cupped fashion, etc). I can't recall exactly but I think your caster angle ought to be around 2 degrees (negative) and you ought to have about 1/8 inch toe-in or a bit less. Toe-in is not going to cause this by itself but in concert with the wrong caster angle (or a positive caster angle) it can make it worse. If you're curious about your caster angle, here is a way to get an idea of what you have: Drive around in your neighborhood, turning right and left at each intersection. Is it very easy to turn your truck? That could indicate too small of a caster angle. If it is very difficult to turn it, that indicates you have too much caster. Too little caster will be what causes your steering to go all wonky. With too much caster your wheels will be given a lot more downward force on top of that caster angle keeping them going straight and when you turn you will literally be lifting the whole front end up. If you get too much caster and hit a bump on the highway, the steering wheel will usually kick back at you. One more thing about caster: caster must be checked and adjusted with your truck sitting on the ground as it will be driven. Checking it with the front end jacked up is meaningless. If the back end of your truck sits higher than the front, you will lose your caster angle. If the back end of your truck sits lower than the front, you will conversely gain caster angle. I've seen friends of mine create a death machine by putting tall tires/wheels on the back while using small tires/wheels on the front. They think it looks neat but it will make the truck wander around like a drunk billy goat and can induce all manner of steering wobbles and shakes because the weight and angle are not correct and that lets the wheels pretty well go where they will. In Jeeps this problem is very common and is known as the "Jeep Death Wobble."

If the alignment was/is not correct the tires may be cupping, it will shake one wheel in one direction then the other wheel in the opposite direction.

Check your frame for cracks or breaks. Also check the crossmember rivets. Look carefully with lots of light to help your eyes. Don’t ask me how I know.

great idea , thanks

I had ‘death wobble’ on a school bus I was driving, tires were severely worn. Apparently no one else reported it!

Ed

Or maybe they just didn't drive as fast as you??