Odd driveshaft vibration comes and goes

[David Edgerton]

2 pc rear driveshaft, changed the centre u joint today as it was creating vibration, rusted in the cups. Now vibration up to 75 kph and above that it suddenly goes away. Foot off the gas at 80 and vibration returns. Next thing to check or just change the other 2 u joints?

 

[Radiohead]

How loose is the carrier bearing?
I change all u-joints at the same time. Logic - one took a ****, so it's friends can't be too far behind.

 

[Khayward]

I've experienced u-joints that were bad out of the box, but usually bad joints will be a problem at 50mph, rather than all the way up. Carrier bearing is worth checking into.

 

[David Edgerton]

Ok, lifted the rear end. U joints are good at diff and trans. Center yoke, the rubber holder is quite loose in the bracket but tight on the shaft. Like the rubber shrank. I can move the driveshaft up and down about 1/8". No good right? Also noticed that the part that slips around the spine end has a wobble on the outside of the casting. Is this ok? The spline fit was tight and no play when I re assembled it. When up to speed, 1/4" wobble at the carrier location.

 

[David Edgerton]

I'll try to video and post somewhere.

 

[David Edgerton]

Ok worked on it again. Took all apart and reassembled to make sure. With rear driveline off the slip line at the carrier bearing I spun up the trans. No vibration or bend to the spline. Next looked at propeller joint, no binding at all. Moves cleanly.
Set end of the driveshaft yoke horizontal, slipped on the rear shaft on the spline, making sure the front end yoke was also horizontal.
Put on rear bolts. Lifted wheels off ground and spun up to 60mph. Vibrated like a bi--ch. The front yoke of the propeller shaft just rear of the spline slip joint has always not been parallel to the spline shaft. Visible wobbly.
Can this part wear out? Replace rear drive shaft?

 

[mtnmankev]

Both the slip yoke and spline do wear, not always at the same rate.
There should be absolute miniscule wobble on the slip yoke/spline unit.
If the U-joints are all good, and there is no slop in the carrier bearing assembly, and no wear on the yoke at the rear axle, I would take a REAL close look at the slip yoke/spline.
As long as the driveshaft isn't bent or otherwise damaged, a good driveshaft shop can replace the spline and rebalance the entire driveshaft, and all should be good.
I hope this helps .........