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!