that sounds like the center bearing to me

 

I have needed to replace the center bearing on both of my 240s and in each case there was no difference in the noise in load and no-load conditions. The center bearing makes a high-pitched whine (more like a squeak). If it is rumbling, it may be the u-joints.

To check the bearing, remove center carrier bearing brace. You can then pull the rubber off the bearing (it just sits in there). Wiggle the outer race, if there is any play then it is bad. Rotate the outer race, if it feels bumpy when rotating, then it is bad.

To check the u-joints, just grab the drive shaft near each joint and check for lateral or torsional play. If there is any play in the u-joint, it needs replacement.

Good luck

 

Thanks act1292, I'll check those things out as well. Probably just replace the dang center bearing since I have the parts. Really don't want to replace the u-joints so I'll get under there and mess around with the driveline for a while.

A few days ago I discovered that the belts were all about to break and the AC wasn't tensioned correctly (way too loose). Could this be a cause of some of the noise/shaking that is going on with the car?

 

Few more questions, just to make sure I'm headed in the right direction

Just to review the rumbling is a mix of vibration and thumping. It almost sounds like a loose shock mount, and the noise has sounded more noticable when I hit a hole in the road which makes me wonder if something is just loose in the rear end suspension and bumping.

I notice it the most when the car is basically sitting at a stoplight and in DRIVE. As soon as I put the car in Neutral it all goes away. It feels like it is coming from the rear end of the car. The noise is fairly consistent when driving, doesn't come and go a whole lot.

Soon I'll get under the car and have a closer look, it would be great to have a list of potential problems to look at while I'm under there. So far I have,

1. Center bearing
2. Motor/tranny mount.
3. rear suspension
4. Differential??? (sure hope no issues here)

Thanks

 

if it does it at a stop and in gear, that just about eliminates suspension and differential issues. those are all things that would only manifest while moving.

I'd be looking at that center bearing as in gear at a stop, the engine is pushing against it through the torque converter, and I'd be looking at the differential mounts.

 

finally had some time today to goof around with the car for a while. For some reason I was looking at the back end of the car and saw that one of the muffler hanger bolts was rubbing against the body! I shook the bumper and sure enough, that was the "thumping" noise I had been hearing in the back end.

But why was it doing it at red lights? I decided to try and swap out the center bearing, but stopped when I noticed that the transmission mount was literally falling in pieces and there was some fresh tranny fluid dripping off of it, so I figured that most likely the sagging tranny was the vibration issue and what was causing the muffler to bang around in the back. Threw a new mount on there and it's running MUCH smoother now. (here's hoping whatever it was that was leaking is mostly stopped now that the transmission is in it's proper place again)

Still can hear a whine while driving though which really becomes detectable at about 25-30 MPH. I can't tell if it's coming from the front wheels or the driveline (center bearing still a culprit?). I'll do some more investigating and report back soon.

 

put it in neutral, block the front tires, parking brake off, put both sides of the rear axle on jack stands, and spin the rear wheels, does anything feel or sound crunchy ? center bearings definitely can whine if they are bad.

if you're brave, start the car and put it in gear with the axles on jack stands, just let off the brake gently so the wheels spin up slowly and don't jerk it off the stand... now get out listen carefully... gentle on the brake to stop the wheels, back into neutral and engine off before you do anything else.

 

I've not changed a center bearing myself, but it looks to be a fairly simple process. the axle is bolted to the back of the tranny with a flange plate and 4 bolts, same thing at the differential end. the center bearing is mounted on a plate thats bolted up to the car frame, and a couple rubber bushing things around it (I'd replace the whole mess if I was doing it, just because I wouldn't want to have to do it again).

I'd want a torque wrench (probably both a 1/2 and 3/8 drive for their different ranges) and for sure good 6 point sockets in 3/8 and 1/2, not just that cheezy little chinese 12 point 3/8 kit you carry in the boot for emergencies

 

Getting the drive shaft off is pretty straightforward as Pierce described. Make sure you mark the front and rear shaft so they go back together the same.

The difficult part is getting the old bearing off the front shaft and the new one on. It is pressed on and if you don't have a press, it is probably best to take it into a shop and have them press the old one off and the new one on.

Good luck