It definitely sounds more and more like the U-joint. When it is jacked up have someone move the front wheel forward and backward while you are underneath listening. Show them what you did to get the noise. It should be fairly obvious where the sound is coming from if it is the U-joint. I would not drive it until you get it fixed. If it goes completely it can cause some additional and expensive damage.

 

I think everyone's missing that you're saying that the clunking noise is *repetitive* when you're under load -- it's not one clunk when you take off, it's clunka-clunka-clunka, with (I would guess) a volume proportional to the torque, and a rep rate proportional to the road speed.

Is that correct?

Given that, folks, any thoughts? Sounds like something's slipping somewhere: loose clutches in the AT, perhaps?

 

I don't think it is inside the transmission at all, I don't think he is getting power loss when this happens, I think he is saying that he slows down to stop the clunking.

Being repetetive it has to do with something that rotates or is moving to allow it to hit another part then slam back down and then do it again.

If it is a u joint then you should be able to pick it out when the vehicle is on jack stands, for it to be that bad to hear at speed then it should be sticking or something while turning it yourself.

I am not sure where to go look from here. Maybe just take off the driveshafts and see if you can feel it by hand when they are off.

 

I didn't miss that it was a repetitive noise. A U-Joint will do that when they get bad enough. When they first start to go bad they will only clunk when you shift gears or take off from a stop. As it gets worse it will begin making the noise under heavy loads or high speeds. And it will continue to worse and make the noise more often until it does it continually. At this point it is a ticking time bomb and could go at any time.

It should be very obvious if that is it or not. Jack it up, get under it and have somebody rotate the front wheels back and forth. It will either make the noise or it wont but you should be close enough to tell.

 

Ah. It's been a long time since I've had a bad U-joint; I'd forgotten that.

 

I never let mine get that far but I have had friends who have let theirs go too long. I've also dealt with that problem with the U-joints on PTO shafts.

 

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There is a test you can do to see if it is the VC. Put the vehicle in LO range and in 1st gear. Then turn in circles with the steering all the way to the left or right. Then let off the accelerator and see if continues or stops. If it comes to a stop, I think that means you have a bad VC. Good Luck!

 

Forgive me for sounding like a moron, but everyone's suddenly started talking about the "VC"... and I can't map that to any component on a Landy; we don't mean "CV" (as in "joint"), do we?

 

VC stands for Viscous Coupling (The device that auto locks your center differential), at least I think thats what Mirko meant.