BradFed

So I have been troubleshooting my 4wd not engaging properly. I have a clunking sound coming from the drivetrain (transfer case, or front diff maybe), and I figured the clunking would go away when I got the 4wd to work.

I got the 4wd to work today by switching the vacuum lines on the front diff actuator. I just bought the truck and I guess the last owner reversed them on accident. I was confused because my transfer case would engage/disengage, and my front axles would lock in, but they would not happen at the same time. I would get one flash of the 4wd light and then nothing. Switching the actuator vacuum lines allowed the 4wd light to come on, and go off like normal. (I have 3.4L Auto with push button 4wd).

Now the real issue. My clunking has gotten worse.

With the front end raised in 2wd - I can spin the front driveshaft, and each of the tires. all 3 components move freely and independently.

But when I spin the front driver's wheel I hear a faint clicking. I guess this may be my clunking when I am on the ground driving. It almost sounds like a bad bearing with balls clicking, but I am not sure. Using a stethoscope, I can hear the noise through the driveshaft, but it gets faint in the transfer case, and louder in the front diff.

Here's where I am really thrown for a loop. When I engage 4wd with the front end lifted - the driveshaft locks, and the wheels engage, BUT when I turn one wheel - the opposite wheel spins in opposition. So as I am turning one wheel clockwise, the other is moving counterclockwise. Doesn't matter forward or reverse, or which side I spin. The wheels are locked in opposition.

The previous owner said something about have the front diff replaced, and I have tried contacting him to speak with his mechanic to help troubleshoot, but cannot reach him now - go figure. I got a good deal for the rig, so I am not really upset. I just need help fixing this!

I can drive up to highway speed, but I have a good shaking, and the truck feels like it is being held back in some way. At speeds under 10mph, I can distinctly hear the clunking in the drivetrain in both 4wd and 2wd. HI and LO. I am worried to drive it anymore until I figure this out.

Also when I bought it the exhaust was cut right before the muffler, but the muffler was not removed. Welding the pipe back together is when the clunking became noticeable to me. I am thinking he cut the pipe just to hide the clunking sound and sell it. But who knows.

Thanks for much for the help in advance!

BradFed

OK well my bad on the wheels spinning in opposition. I guess that is indicative of proper functioning. I learn something new every day.

So good news is 4wd works properly, though makes a good and loud clunk on disengagement.

Bad news is noise in the diff.

The wheel bearings all appear solid with no play. So I guess that leaves the diff.

Using this link:
http://www.onallcylinders.com/2012/0...veline-noises/

It seems like I may be closest to:

Noise: Banging or heavy clicking every two to three feet during acceleration and deceleration
Cause: Damaged or broken pinion gear tooth or teeth

Noise: Low-pitch rumble at all speeds over 20 miles per hour
Cause: Worn carrier bearings

Noise: Clunking when depressing the throttle pedal (takeoff)
Cause: Worn U-joints; worn spider gears; worn axle splines; excessive gear backlash; loose yoke splines; worn slip yoke splines

Noise: Steady vibration that increases with speed
Cause: Worn U-joint or out-of-balance driveshaft

The U-joints seems solid with no play and are freshly greased.

The transfer case and front diff were both a little low on gear oil, and I topped them off today.

The most that I have done with drivetrain before was replacing U-joints, and wheel bearings. I have never dug into a diff before, but it is sounding like I may need to replace mine, or rebuild. Which would you guys recommend from the sounds of my situation?

BradFed

One more update. Just went for another test drive and wanted to clarify some noises.

between 5-10mph the clunking noise is very distinct. da-duh-da-duh-da-duh-da is more precise In 4wd, same pace, but twice as loud.

After 10 mph, that noise kind of goes away. Mild vibration in the car after that - increasing with speed. Tires are worn a little uneven, so it's hard to tell what's causing what.

Cruising around 45mph, there is a whirring/sub-screeching noise. It's hard to describe. It's not a screech or a squeal, but it sounds like it could go there. Like a metal on metal whirring. Pretty loud, as in other cars can also hear it when cruising at 45mph.

I am going to drive it tomorrow probably an hour and a half total. I probably shouldn't but it still drives so I will.