U-joint(s) or driveshaft? Or something else?

[King_V]

Ok, so, this happened, naturally, on a Saturday evening. Mechanic's closed until Monday, etc.

But, at some point, I started hearing some light, thin metallic sound coming irregularlty - sort of like something sitting in the trunk was rattling. But nothing.

Then a very low, subdued growl, that changed in pitch with vehicle speed, rather than engine speed. Didn't seem to be coming from the front (which would've made me suspect front wheel bearings). Can feel the vibration in the car, but it's very slight.

Those things make me suspicious of a particular potential issue. Get home last night, so today, I take a look underneath, with a back wheel lifted and the car in gear. There is definitely a slight wobble in the driveshaft, and this weird "tinking" noise coming, but very irregularly, almost as if of something was tapping the exhaust pipes, but not at all consistently or steadily. Seems to be coming from the rear one as best as I can tell.

Is this most likely to be a U-Joint, and I'm hearing bits of needle bearings going flying? If so, I'm lucky, since I was looking at it, and nothing it my eyes! Or could it be something with the driveshaft itself?

Thoughts? I suspect it's the u-joint, but my inner-paranoia wants to cover all bases.

[sly]

shift from R to D a few times. If you hear clank... probably a u-joint or trans mount. if you only hear it running down the road, probably a rear axle bearing.

[gadget73]

Pull the driveshaft and roll the U joints through their range of motion. If they don't move smoothly, thats your problem. They don't always get so bad as to clang before you feel or hear something wrong.

If thats good, look for oil leakage at the rear drums. Also check the rear gear oil level while you're in there. Leaks indicate possible problems with the bearings, but low oil will definitely kill them.

[King_V]

As far as I know, there are no leaks, but I didn't have time to do more than a cursory check.

Also check the rear gear oil level while you're in there. Leaks indicate possible problems with the bearings, but low oil will definitely kill them.

I will admit right up front that I have no idea how to check that. I mean, I am almost certain there's a drain plug or something that looks like that on the differential somewhere, but I had always assumed that, if I open it, oil will start coming out.

[gadget73]

the fill plug is up top, just rearward of where the driveshaft flange is. It uses a 3/8" extension to unthread. Basically the oil level is supposed to be up to the bottom of the threads at the drain plug. If some oil starts to run out when the plug is pulled, its full. If not, you can take a piece of wire and stick in there to get an idea of how far down it is and top up as needed. Its 80w90 gear oil.

[King_V]

Wait, so there's a fill plug and a drain plug? Presumably the latter being lower down?

[Piece-it pete]

You drain it by pulling the cover, which ultimately means you'll also be drenched in perhaps the vilest smelling thing that comes out of a car. Which lingers to boot.

Pete

[87gtVIC]

What he said. No drain plug only fill.

[gadget73]

you don't really get drenched. its not quite as horrible as a trans service, but it is messy and very smelly. Gear oil smells like dead dinosaur when fresh, it smells like rotten dead dinosaur when its old. The smurf jizz for limited slip axles makes it even worse.

[King_V]

ROFLMAO! Man, these are descriptions I'm going to HAVE to remember!

Though I might get some strange looks when I say "I need the dead dino replaced, and it's a limited-slip, so add some smurf jizz..."

[slack]

I spilled some of the old gear oil in my trunk. The car reeked of that stuff for MONTHS. I ended up throwing out the trunk carpet entirely. Doesn't smell anymore but damn. That's the last time I put a vat of that in the trunk.

[TwoTone_90GS]

If you decide to tackle the job yourself, wear clothes that you are willing to throw away afterward. Getting any of that fluid, new or old, on your clothes will ruin them. Gear oil is one of the most wretched things I have ever had the displeasure of smelling.

[Piece-it pete]

The solution!

http://www.ebay.com/itm/75W90-GEAR-OIL-32OZ-SYNTHETIC-NEW-GL-5-New-Grape-Scent-88900401-ACDelco10-4016-/161254056669?pt=Motors_Car_Truck_Parts_Accessories&hash=item258b7da2dd&vxp=mtr

Pete

[King_V]

ROFLMAO! I can't believe that's a real product!

Ok, update. So, as I didn't have the correct tools or expertise to do this (I've done U-joints from cars where they were held with U-bolts or something similar... about 20 years ago), so I took it to a local shop.

I should also clarify that the groan/roar that's proportional to speed almost sounds like a much MUCH quieter version of driving on a rumble strip.

Anyway, so my mechanic calls me, and lets me know that he's taken it for a drive on the road, and gotten it up on the lift and run it, using his stethoscope to try to pinpoint thing. There was no "tinking" and what little noise he heard seemed to be coming from the differential.

He checked, and the gear oil level is correct. He also says it's NOT axle bearings.

Admittedly, he was otherwise at a loss. He said the only thing he can say is that his truck has had the same noise for about 5 years as he's hearing in my car.

Only thing he charged me for was the quart of oil he added because the Check Oil light came on.

So I pick up the car last night, and I try driving it.

No tinking noise, at all, regardless of speed.

It was really hard to hear the groan/growl noise. I mostly couldn't hear it. Once or twice I *thought* I heard it briefly, but I really could not be sure.


Bizarre.


This morning, heading to work, for the first few minutes, it was just like last night. Afterward, that low-groan-proportional-to-speed aka like-the-world's-most-modest-rumble-strip noise came back. Not as loud as it was Saturday evening, but there. Still no "tinking" though, that seems to just have gone away.

I actually glared at the dashboard and said to the car "Ok, now you're just messing with me, aren't you?"


I originally thought rear-u-joint or differential because that's where I heard the "tinking" noise coming from. Not sure where the quiet-rumble-strip noise is coming from. At this point, I might even check the front wheel bearings for anything obviously wrong (though if it's subtle, I will NOT find it!)

Other thoughts? Or have I just caused more puzzled head-scratching?

[sxcpotatoes]

Stereo ground. I know the radio or tape deck on these things have been known to have a growl eminate from the speakers increasing in pitch with acceleration/speed. If you have your stereo faded back to the rear it may explain why you thought the growl was coming from the rear u-joints.