Is it my VC or my CV?

[Skydmark1]

Hey all, I've been doing some searching and reading here about bad viscous couplers and trying to diagnose an issue with my Mountaineer. It's AWD and has a loud vibrating rumble. It starts at around 15mph and gets worse as speed increases. It follows speed, not engine RPM. My first thought was that I have a bad VC because when I bought this vehicle it has 4 different brands of tires on it. However, I'm now wondering if it's actually the CV joint on the front driveshaft.

I don't get any hopping or binding on tight turns which I'm hoping may rule out a bad VC?? On the flip side, when I crawled underneath I couldn't get any play in the CV either. It does look like it could be the original CV and the vehicle has 175k miles on it.

I'd much rather replace the CV joint than look for a rebuilt Transfer case.

Anyone have any thoughts on this? I might just spend the $80 and replace the CV joint, but money is tight this time of year and I'm trying to get it on the road.

 

[koda2000]

CV's usually click, rather than rumble, when they go bad. I just replaced the front driveshaft CV on my daughter's AWD '00 Mountaineer. Pretty easy job. It would click like crazy even when rolling out of gear and 2 MPH.

 

[Skydmark1]

I was thinking that as well, there's no clicking. So what's causing the issue? Am I looking at a bad VC?

 

[rathrbcruisin]

wheel bearings can rumble, grind and howl.

 

[chefduane]

Same symptoms I had. Eventually turned out to be a bad U-joint. Get the vehicle up to the speed when the noise occurs, then carefully shift into Neutral and coast for bit. If the noise still happens then its got to be engine and/or possible bearing related. If it doesn't, then its most likely drivetrain related.

 

[Skydmark1]

wheel bearings can rumble, grind and howl.

That did cross my mind, maybe I will jack it up today and give everything a wiggle. It looks like some front end parts were recently replaced but maybe they skipped the wheel bearings.

It doesn't sound like it would be the VC though? this is my first AWD so haven't had to deal with the whole viscous coupling before.

 

[rathrbcruisin]

this is my first AWD too. from what i have read if it fails it could be either a total lockup, or no power to the front at all. I know CV joints make more than clicking sounds. vibrations, grinding. Just because a CV joint is new doesnt mean its a good one. My father-in-law replaced his half shaft in his taurus 3 times, all with new ones, before he got a good one. do you feel vibrations anywhere? like in the steering wheel, or the drive train? like in the seat.

 

[Skydmark1]

Ya, I can feel some vibrating in the floor. After a little investigating today I found the upper driver's side ball joint is pretty bad. Wondering if that might be the source of my sound

 

[Ryan87LX]

The CV is the weak link in that setup. So if the transfer case starts to bind up, the CV will fail. Once that happens, you don't feel the binding as much, so you replace the CV joint, and then the bind is back, and the cycle repeats.

CV is really easy to tell if it's bad or not, just grab the driveshaft with your hand and try to move it. A bad CV (or u-joint) will allow the shaft to move around quite a bit.

 

[Skydmark1]

The front driveshaft is tight, I can't get it to budge at all.....yes it's in neutral

The only thing I can find wrong in the front is that upper ball joint

 

[rwcfrank]

Skydmark, did you ever find r fix this problem? Mine is doing the same thing!