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post number 13 discusses results of the u-joint replacement

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99 silverado ext cab,
2WD 5spd manual
98k miles
tires have less than 10k miles
there is no North-South or East-West play in the front wheels

vibration between 40-45mph and again at 55-65mph
had wheels spin balanced twice at one shop, then a third time at another
still vibrates

First question - how precise is computerized spin balancing? Is this
typical: the mechanic balanced one wheel to 0.00, took it off the
machine, put it back on the machine. it was then off by 1/2ounce.
he rebalanced it to 0.00, then did the same test again. happened
three times. it was always off by 1/4 to 1.0 ounces.

Second - there is a tiny bit of rotational play in the u-joint next to the transmission,
major rotational play in the middle u-joint (most of it seems to be at just one of the
four points), and no rotational play in the u-joint next to the differential. Is any
amount of play acceptable or safe? How big a job would it be to
replace them myself?

Third, In neutral with the clutch out, there also seems to be very
noticeable play forward of the first u-joint. What might that indicate?

Fourth - how do you inspect the carrier bearing?

thanks in advance,
mike

 

i found these websites for u-joint repairs:

http://www.stu-offroad.com/axle/ujoint1/u-joint-1.htm

http://forums.pickuptruck.com/ubbthr...=522046&page=1

http://tinyurl.com/yuzwe8 or: vib at 30mph

sat mech:: u-joint replacement

car care clinic: u-joints

 

Dose it vibrate more when you let off the gas at higher speeds? If so then youre ujoint is bad

 

The vibration between 40-45mph is fairly robust. it persists under accelleration, deceleration, clutch in, clutch out/in neutral, and seems to have about the same frequency in any gear (running at 40-45mph) (seems to be independent of RPM)

It then quiets down and is vibration free between 50-60mph.

However, this evening I noticed the vibration occuring during light or medium acceleration anywhere in that range 50-60mph

The 60-65mph vibration is present when driving at constant speed on level ground. It goes away when the clutch is in, or when it is out and in neutral.

I know the middle u-joint is bad, the the front u-joint -s worn. I don't know if the bad u-joint(s) are causing the vibration or not, but having seen how bad the middle one is, I'm a bit scared driving. So those two will get replaced. It would be nice if this fixes the vibration problem too.

Still don't know how to assess the carrier bearing, or what the significance is of the play that exists in front of the front u-joint.

 

might need to get youre drive shaft balanced

 

Is the vibration in the steering wheel or in the seat?

If its comming from the steering wheel then it is up front, otherwise its in the rear.

Could be:
1. Out of balance
2. Bent wheel
3. Broken belt in tire
4. Bad balance (If done incorrectly, it can still be "unbalanced")
5. Out of alignment
6. Feathered or cupped tire tread
7. Brakes hanging up
8. Bad shocks or steering/suspension components.

Most tire places just throw it on and balance it real quick. Make sure the tire guy sets the machine up before balanceing. Makes sure he uses the correct measurements and makes sure he is taking the time to place the weights on correctly.

If you still have a vibration and you have identified the problem tire or tires.
A. Have them pull the tire off the wheel and place it 180 degrees from its original position and rebalance.
B. Have alignment checked.
C. Makes sure there are no bumps or valleys on the tread of the tire due to alignment wear or worn parts.

 

Your problem sounds exactly like a worn U-joint. Even if there is no motion in the drive shaft (fore and aft play or left to right), they could be dry and when there is no grease, they fight the driveshaft. One lobe is probably bad and each revolution under engine load you can feel the lobe fighting the turning of the drive shaft. If you can't find the problem U-joint then replace the rear-most u-joint first as this is usually the most troublesome u-joint on trucks.

 

My ujoint had the bearings out and practically was running running metal to metal. All it did was make a loud noise on the take off before I changed them, with no vibration. If its in the front you might want to check your motor mounts. That tends to create a lot of vibration.

 

True, or a transmission mount. My 91' shook alot when my rearmost U-joint went bad.

 

04BLKCHEVY - I think I have the same issue you described above. Did you just change the rear u joint or did you change them all? How hard is it?