bikedave99

I just ran through the diagnosis and repair of a shudder/clunking/vibration issue on my 1998 Toyota Tacoma. It is a 3.4L V6, manual transmission with manual locking hubs, but most of the info should apply across the board. Hopefully the below information will help you on your path back to a smooth and quiet (relatively) Tacoma. Please feel free to supplement or correct any of the info below or provide additional tips.

First off, here were my symptoms:
1) Since I purchased the truck with 130k miles on it, it had a small shudder that occurred only in second gear for a few seconds during acceleration. More recently this became more pronounced and would appear at random across the first three gear accelerating.
2) It developed a hum/whine at highway speeds.
3) When slowing down it started producing a fairly heavy clunk clunk clunk from about 10mph to stop. The clunking seems to definitely come from the front end of the truck, and possibly the driver's side.

From researching on here and around the web, I concluded it could be one of these things:
1) Front or rear differential ring gear or pinion chipped
2) Bad wheel bearing
3) CV axle failing
4) Improper/inadequate grease at front wheel hub engagement splines
5) Failing clutch or flywheel issue
6) Wheel or tire imbalance
7) Worn steering components
8) Bearing failure at output or input shaft on transfer case
9) Bad U-joints or center carrier bearing.

Tests I performed to eliminate the above (same order and number):
1) Drained and replaced differential fluid. I dragged a magnet through the drained fluid to check for excessive metal shavings or chunks. My fluid was still clean and no metal found.

2) I suspected my front left wheel bearing since I replaced my front right not that long ago. To test this, when the whine/hum or clunk was occurring I steered left and then right as this should be putting more or less pressure on the bearing and change the pitch or volume of the noise. Don't do this at highway speed obviously. Alternatively, after a driving for a while, pull off the road and just go around and feel how hot each of your hubs are. Are any hotter than the others? If so, make sure it isn't your brakes rubbing causing it to heat up. Also, jack up the each tire and grasping it firmly, check it for excess play per the FSM. In my case, nothing was hotter than usual and steering back and forth did not change the noise.

3) The CV axle test is pretty much the same as the above. Driving slowing in a parking lot and turning tightly one way and then the other should cause the CV axle to make noise and then stop making noise as it is loaded and unloaded. As stated above, turning had no effect on the noise my truck was making.

4) If your (manual) hubs are not locking and unlocking properly, they can cause noise as well. I don't know exactly how to test this except to pull the wheel and locking hub and off and check for grooving in the engagement splines, clean it up and lightly re-grease. Both my hubs and splines were in good condition.

5) If it is your clutch or flywheel generating the noise, you should be able to isolate the noise by pushing the clutch pedal in and out when it is making noise. Pushing the clutch in and revving the motor did not stop or change the noise my truck was making.

6) If your wheel or tire is out of balance, the vibration/noise should vary with your speed. It should also correspond directly to each rotation of the tire. In other words if you slow down and listen, the noise or vibration/clunk should occur with each rotation of the tire. In my case, I noticed that the low speed clunking I was getting was happening more than once per tire rotation. This told me that my tires and wheels were fine, and, most likely, my wheel bearings. A wheel bearing noise is typically a constant noise or a once per revolution noise.

7) Worn steering bushing or components can cause some vibrations and noise as well. To check mine, I jacked up the front end of the truck and grabbed one tire and jerked it back and forth to see if there was excessive play. There wasn't. With the vehicle back on the ground you can also just grab various component of the steering linkage and yank on them to see if anything is loose. All of this was tight on my truck.

8) To check the input and output shaft bearing on the transfer case I just grabbed drive shafts at each side and pushed it up and down and sided to side to see if there was much play. There wasn't.

9) To check the u-joints and carrier bearings on the truck, you can also slide under and yank them around to check for play. There should not be any except for the carrier bearing. From my research, it seems like the carrier bearing can have up to 1/4"-1/2" of wiggle still be ok if it spins fine. My carrier bearing and u-joints did not have any play in them with this test. However, to eliminate them completely I decided to pull the drivelines anyway. I first pulled the front driveshaft off (careful to mark exactly how it comes up so you line it up and bolt it back on in the exact same orientation it was removed), then went for a drive. The noise/vibration/clunk was still present. So, I reinstalled the front driveshaft and pulled the rear. I locked the front hubs, put it in 4wd and went for a spin. The symptoms all disappeared. I got back to the house and check the u-joints on the rear driveline. The double cardon joint moved fine, the rear u-joint was a little worn (when I rotated the joint, it preferred to stay in a "groove"). But, the front u-joint was almost fully locked up in one direction. So, I replaced both u-joints on the rear shaft and that solved the problem! I also shimmed my carrier bearing down a little to get the driveshaft more straight in a line.