My Taco has had a vibration that has been driving me nuts since I got it.

I was just under it this afternoon adjusting the parking brake and while I had it up on stands I wiggled the driveshaft. It shakes. And where the shaft goes into the rear differential it wiggles to. I spin the rear wheels forward then stop it quick with my hands to back in reverse there is a noticeable clunk.

Is this U-joint related?

Is there a better way to check for U-joint issues?

Could this be the vibration I feel when stopped at a red light?

Lastly, random question, why does one wheel spin forward and the other backward when on jack stands?

Thanks all.

 

U joint play will be evident at the joints, not at the differentials. It's normal for the driveshaft to be able to spin back and forth a bit, there is a bit of play in the differential gears. If you hold both sides of a joint and try to twist it and there is any play, that's a bad u joint. The wheels spin different directions while off the ground due to the design of the differential. Are you familiar with how a differential works?

 

To start, I guess I should make sure I know what a U-joint is and where it is located. It's the cross-looking thing at the end of the driveshaft that goes into the diff, right?

How do I grab it on both sides and twist it? I'm not sure I get this part.

And no, I don't know how a diff works but would love to learn that.

Thanks for the reply.

 

I think you have the general idea of what a u joint is. There are multiple of them on your truck. You'll have more than one on each driveshaft. It's basically an X with a cap on each leg with needle bearings inside to let the caps rotate. If you don't lubricate the needle joints and let them get dry, they wear out, turn to dust, and voila: play in your u joints. just grab the driveshaft in 2 places with the u joint in between and see if there is any play when you try to rotate your hands in different directions. There should be NO play.

How a differential works - http://www.howstuffworks.com/differential.htm

 

U-Joints can also sieze from lack of grease and not feel loose. This has happened to me before and it took longer to find the vibration since I thought the U-Joint was OK.

 

When mine went out I got a twitching noise while on the gas only, because you put the drive train under stress and the bad ujoints squeak and chirp.

 

So I looked for a zerk fitting to grease them but I can't seem to find it. Are some units just sealed like ball joints?

 

Toyota OEM have zerks.....aftermarket....can't say.
The zerk is hiding in the intersection of the two arms and can be difficult to see if covered in grease and gunk.

 

2wd (5-lug) shafts may not have zerks. The Prerunners use the same rear
driveline stuff as the 4wdl afaik, so they should have zerks. Some are hard to see, especially if they haven't been lubed in a long time.