Good evening,

There are so many ways to miss the problem of vibrations and so many ways to screw up parts while putting in new ones. Here I will tell most everything about finding driveline problems and how to put in parts the right way.

The following is a list of reasons to inspect your driveshaft for problems:

1) a clunk when you go into gear or reverse
2) a humming or vibration when you are moving
3) a squeaking that is in time with your tire rotation
4) general inspection with oil change

Here is how to inspect your driveshaft. If you have a 2 piece do all of this, if you have a one piece (automatic) you do not have the slip and spline or bearing, just worry about the transmission yoke, 2 joints, and tube.

Start with a manual wiggle. hold your front yoke on the tranny, try to shake it up and down and see if there is a lot more movement than there used to be. This means the transmission bushing is worn. Sometimes tranny fluid will leak out at the same time if the seal is gone.

Hold the yoke welded into the tube and the yoke going into the tranny and twist back and forth trying to wiggle the u joint. If ANY movement is there you need a new joint.

If you have a steady bearing shake the shaft in it. If the rubber is worn out that supports it, get a new bearing as it comes with the rubber mount and hanger.

hold the slip yoke that goes over the spline and try to twist it back and forth, and up and down. If it is very loose it needs one or both parts replaced at a driveline shop, if it is just a little loose it needs grease. (Slip yokes have a hole in the plug that loose grease over time. This hole prevents over greasing and filling the slip so no movement at all can occur when the suspension works. If over greased in winter, sometimes the hole is not enough and the whole plug pops out. This is very very bad.

Check the 2nd u joint for movement by twisting both the slip yoke and weld yoke like the first one.

Check for dents in she shaft.

Check the third u joint like the other 2.

Now it is time for a running check. Sometimes joints are dry inside or seized. This is not detectable with trying to move joints by hand and this is missed by any and all oil change shops as you MUST run the truck in the air to see this.

Jack up rear end and put stands under axle.

Start truck and put in gear and let it idle running.

If your shaft is jumping up and down, or belly flopping, or one end or both ends seem to be hopping to the point that your main tube is hopping rather than spinning perfectly you have to remove the shaft and inspect it in a vise.

Seized or dry joints will turn but not smoothly and will cause a squeak or a vibration, but cannot be felt by hand unless they are EXTREMELY worn.

When your shaft is held gently in a vise (do not crush tube or hold tightly) move your joints full range. any clicking, stiffness, crunching, seizing, clicking or sloppy shaking in caps means they need to be changed.

If you have a steady bearing, give it a twirl. It should move no more than 2 turns, and it should be stiff and smooth. If your bearing rumbles, chatters, or spins fery freely around and around with no resistance it is dry and needs changing.

If you have a slip and spline, try holding the shaft with the spline in the vise, and slide the slip on. wiggle it up and down and side to side. The slip should not move up and down (if it moves only a hair grease it) and very little from side to side. Side to side is taken up while torque is put on it, but up and down will let your shaft move too much and not spin in a circle, it will whip around as it spins. Take you shaft to a driveline shop.

While your shaft is out, look at the ATS (yoke on automatic transmissions) on your shaft and see if it has only a natural wear mark, or a deep cut or groove. If so replace it is it will flop in the tranny and leak transmission fluid.

Now that you know what parts need changing and have them changed and greased etc, take the shaft in to have it balanced. Even though new parts are all machined, they can be slightly crooked or uneven, and your shavt will be heavy in different areas and parts. Have your shaft balanced so that your new parts do not wear out early. Your shaft lasted this long as it was balanced the first time, if it is not straightened and balanced now your new parts will not last long at all.

Any time you change any moving or spinning parts on your driveline you should have those parts balanced.

Rob