Possible issues with rear live axle??
 

My daughter's 2000 2WD had some issues of shaking and when I checked the vehicle out I found the rear shoes (especially the passenger side) was down to the metal on the edges. I replaced the shoes and they seem to work fine. However, she stated yesterday that the vehicle had a shake at highway speeds that scared her. I checked out all of my work as well as had her have her tires rotated and balanced which was more than needed. The issue wasn't alleviated.

I just jacked up the rear and put her in neutral and spun the tires and checked the propeller shaft joints. The driver's side tire, when spun correlated to the drive shaft turning as expected. However, when I spun the passenger side tire, there was a 1/4 tire turn delay until the driveshaft spun, in both directions, then it spun the same, and then it had a delay again. I honestly have never seen this.

Any ideas?

Were you watching the other side tire at the same time to see if it was swapping between spinning the driveshaft and opposite tire?

Even then, the 2WD prop shaft (from trans to diff) is known to go bad on the 2WD's with age. Both the u-joints and the shaft itself can have problems. There is a rubber coupler between an inner and outer shaft that wears with time and causes vibrations at highway speed (50-70mph) that feels just like bad u-joints or an out of balance driveshaft. If the rubber section goes bad, the only solution is a complete new driveshaft.

Vibration/buzz normally means driveshaft.

Shaking/wobbling normally means tires or something that rotates at that speed (brakes, etc.).

-Charlie

What you're feeling/seeing is backlash in the rear differential and it's normal operation. All vehicles have backlash but you will get more as components wear.

Can you describe your problem in more detail? Speed, accelerating/braking/coasting, turning, feel it in the your seat, steering wheel shaking?

Thanks for your feedback.

So I went out and test drove it with your inquiries in mind:

County road test:
Slow acceleration to 50 mph nothing overtly noticeable.
However, when backing off the gas down a long hill, there was slight shaking in the steering wheel, shifter and seat as it slowed to 45. Acceleration back to 50 mph seemed to reduce the recent vibration.

Highway test:
Moderate acceleration to 80 mph, again, nothing overtly noticeable.
When backing off the gas there as a noticeable shake in the steering and seat. When I performed this again (accelerate to 80 or so cruising speed and then reduced acceleration), it seems the seat area vibration is most pronounced, almost creating a noise or hum along with the feeling of the vibration.

Thanks for your reply Charlie. My daughter had the tires rotated and balanced, and the alignment seems to be true in road tests, but I could have that checked as well.

It seems that there is a shake/vibration that comes when the truck is decelerating, not under acceleration. (see reply above as I tested this on a County as well as an Interstate road with the same observations.

Also, I just replaced the rotors as my daughter stated that "everyone is telling me it has to be the rotors," even though I disagreed. Well, she bought them, I did the labor, so there's that.

Test drove it and nothing changed for the better.

So is the shaking from the front or the back? How many miles are on this beast? If I was going to check the ujoints, (with trans in neutral, wheels down) I would hold the yoke in one hand and the driveshaft in the other. Try and twist in opposite directions. Muscle them around and look for play. Check the yoke at the 3rd member and the output shaft at the transmission. Does it have a double joint at the trans? As others have mentioned there is also a splined joint in the shaft itself. You can try and push pull and look for deviation...

I can't see feeling this in the steering wheel though.

The 2WD shaft does not have a splined section at the center, it uses a slip yoke at the trans with single joints at each end.

It does seem like the next step is manually checking the driveshaft. 4 nuts/bolts at the rear diff and it will slide out. Check for good operation of the u-joints.

Since it doesn't happen at steady-state cruise, it is less likely to be an issue with the main part of the shaft, but it could still be u-joints.

-Charlie

Can't tell, but the shaking definitely isn't simply the front, that's for sure. The beast has just under 300K.

There is NO play in the u-joints that I can muster out of them at all.

It may not be play, it may be tight spots instead. Pull it out of there and test manually.

-Charlie

So I need to pull the driveshaft to check it correct? I can do that in the AM.

Thanks!

Dave

Will do, thanks!!

I pulled it and the rear U-Joint is free in one joint, but stiff in another joint especially when bent one way over the other.

https://i.imgur.com/u0KwGRh.jpg

Seem like the culprit? Now to figure how to replace it....

Is there any use in cleaning that up really well and then pumping the zerk fittings full of new grease to see if you can bring it back to life? (I don't know the answer.)

I don't know either, but a new MOOG joint is $19, so I went that way. The local machine shop pressed it out and installed the new one for $30, and I thought that quite a good deal as I'd have to use a hammer and some joint support blocks made of wood laying around and be on my knees in the heat more than likely...