Another vibration Problem

[GGOODMAN]

this is for my cousin same truck as mine just green and tan. He's got a vibration at about 40-50mph and when he jumps on brakes. Any slower or faster and it goes away. Here's whats been done in the last three months.
U joints
Ball joints
Rotars turned and new pads installed.
1 pc drive shaft with new u joints put in.
Drove truck in 4 hi problems stayed the same no worse no better.
Tires rotated and balanced.
He changes his oil every 5k and fuel filters every 10k.
I'm running out of ideas I think he got a warped rotar... anybody else care to chime in.

[POWERED SPARKLESS]

What do the tires look like? Are they cupped? I have the same problem and 45 mph but I have a bad cup on them.

[GGOODMAN]

no, nearly new 315/75r16 bfg all terains maybe 12 k rotated and balanced regualrly.

[mrnecsteve]

Originally Posted by GGOODMAN

this is for my cousin same truck as mine just green and tan. He's got a vibration at about 40-50mph and when he jumps on brakes. Any slower or faster and it goes away. Here's whats been done in the last three months.
U joints
Ball joints
Rotars turned and new pads installed.
1 pc drive shaft with new u joints put in.
Drove truck in 4 hi problems stayed the same no worse no better.
Tires rotated and balanced.
He changes his oil every 5k and fuel filters every 10k.
I'm running out of ideas I think he got a warped rotar... anybody else care to chime in.

Sounds like he needs to define the problem even further with some "diagnostic
procedures" USE CAUTION !!
step one : safely put all 4 axels on sturdy jack stands. Run the vehicle thru the gears while someone observes the wheels and tires. Look for abnormalities
especially a deformed tire .Use a visual stationary reference next to the wheels and tires. Apply the brakes and check for smoothness.If nothing found go to step two
step two,take the wheels off. (if drum brakes are involved ,put all lug nuts back onto wheels with equal torque) While keeping your distance and the speed down, observe the drive line. Put on the brakes lightly to simulate a load. Watch the drive shafts for unusual flex or wobble
If I were to take a guess...there is a slipped belt on a tire or the tire is deformed.A slipped belt is something you will feel when braking that seems to come and go. Using this method ,you can begin to isolate: tires and wheels or drive components.
Using this method,I have isolated bad tires.Also, I once found that an aftermarket aluminum wheel was bending the rotors when torqued down.
Exact wheel torque procedures can be critical...aluminum wheels dont bend too much !!!
Stay clear and dont overspin!

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Last edited by mrnecsteve : 07-11-2008 at 05:38 AM.

[04f2504x4]

Originally Posted by POWERED SPARKLESS

What do the tires look like? Are they cupped? I have the same problem and 45 mph but I have a bad cup on them.

I have the same exact problem at 45 miles per hour, it feels like I am driving over a wash board. Since this started I have put on new brakes and rotors all the way around, new tires all the way around and yet it still does this at exactly 45 mph. Wheel bearings feel great when I had it up off the ground trying to figure out what else might be causing this problem. I can't stand to drive 45 mph because of this, it feels just like I am driving over a washboard.

[OregonStroker]

is the truck lifted? how is the suspension?

[RedDye01]

were the u joints tight in the yolks? sometimes if you dont whack them real good so theyre loose before you put the drive line in they can bind just a tiny bit and cause a vibration.

[GGOODMAN]

Trucks lifted seem my sig for details. Dont know shop did the drive shaft. I'll give it a look. He sene developed some ac problems and Ive got to replace my draglink so his vibrations got moved on the list.

[OneTon]

Is it possible the ROTORS were turned too thin? If it only occurs while braking ... I would find it hard to believe it has anything to do with the tires. If it occurs at that speed without braking .. I would say it is a balancing issue ... a LT315/75R16 is alot of tire to balance. Are they static balanced for cosmetic reasons ...?

[04f2504x4]

My truck does it any time you are at 45 mph (accelerating, coasting or braking it does not matter). My truck had 285 75 16's on it and had the same problem. It was not lifted in any way and was 100% stock with only 45,000 miles on it. After 14,000miles of dealing with this vibration I replaced all the brakes, rotors and pads, it was time for them anyway. This done nothing for the vibration. I then thought well maybe the tires are out of balance and I needed new ones anyway, so I replaced them with new ones and Nothing , vibration was still there. I have since put a levelling kit and 315 75 16's and the same vibration is there that was there with the 285 75 16 tires so I really doubt the problem can be blamed specifically on tires or the levelling kit. And the vibration is still at the exact same speed as it was before, at 44 there is little to no vibration, then at 45 it feels like you are on a very large washboard and by 47mph it is smooth as can be again.

I also want to add that my speedo is not calibrated , so the vibration is always at 45mph by the speedometer and not by actual road speed.