Thumping Driveline?

[James Downing]

Ive had this reoccuring sound/feeling for a bit under a week now, I didnt want to call wolf though, so I waited a bit before posting about it. (Im going to tell as much as I can in order to better help you guys diagnose it)

I first noticed it in a parking lot, while going maybe 5 mph going over a speed bump. The car let down over the speedbump, and I felt a slight bump, and a slight sort of "thump" that came from the left-front area.

It has progressed, (or I have just become more preceptive to it) to what feels like a small ball bouncing around inside my tire. It doesnt seem like a regular thump, more sporatic, but occurs maybe once a second when driving through the parking lot.

The noise is slight, and can only be heard if my music is off. But I can feel the bump through the petals.

The noise seems to mainly occur when coasting, and is more of an aggresive thump at slow speeds.

Today I tracked the noise/feeling into 50 mph, and noticed that it was still notable even at that speed, but feels like driving over a VERY slightly rough road... the type of jolt that is so slight, that you would normally shrug it off as hitting a pebble.

My only guesses are that either:
a) something has come off inside the tire
b) a wheel bearing has gone bad
c) something transmission related (but has only shown signs of a 1 second 1-2 shift thus far)
d) cv joint... but doesnt have turning problems

So... thats all I can think of right now, If there are any other questions feel free to ask. I dont really know whats going on.

(oh yeah, I checked the CV joint rubber housing, and they didnt have any oil seeping out)

Thanks everyone, I think Im also going to bring it by my mechanic's monday. I just thought I would get some help diagnosing the problem.

stupid sho...

 

[billyshoe]

I have a winstar that does this and I believe the trans. has a lag time finding the gear it wants to be in on down shift, then hits a bit hard. This is what is does. I don't know why I don't care that much. I never have checked the trans oil level in this vehicle. I just keep driving. I'll maybe check it if it warms up.

 

[Bizzy]

James, have you checked your tires to see if they have any bulges in them? The belts could be separating and it could be causing a bubble. Not a good thing to be driving on if it pops.

 

[James Downing]

Well, the thing is... it doesnt seem to be a regularly occuring bump. Sorta random. But I will give it a double check tomorrow before going out on the parkway (valentines night drive).

I swear it feels like the bearings are sticking.

But the reason I say it could be the cv, is that when there is tension on the drive-train (braking or accellerating or maintaining speed) it doesnt seem to clunk at all, yet when coasting, is when it seems to occur. shrug

 

[TYSHO]

I was having the exact symptoms, clunk right after giving it a little gas, and then one day...I went WOT at 5 mph and...POP...massive grinding. It turned out to be the inner cv joint on the passenger side. The rubber boot was fine, but the fluid was bad.

 

[91taurisho]

The splash shield on the inside of the fender well could have a couple clips missing and when you are just coasting it MIGHT be hitting the tire/strut/anything else. It's just an idea so don't flame me on this but I had the same type of noise at one point. I also had that same noise in my old SLO. It always happened at low speeds right when I'd take off(slowly) and coast at 5mph or so. shrug It COULD also be your strut mount(bearing) is going bad(or starting to show signs of wear). When you accelerate it pushes back on it and it pushes forward on it when decelerating. When you're coasting and you hit just the slightest bump/pebble/anything else in the road it makes that noise. Just another idea... Good luck!

 

[SonicRiot]

It sounds like the wheel bearings or ball bearings are shot and grinding together, eventually seizing up. Pull the wheel off and inspect for rust. They aren't sealed in front, so you should be able to see. The other thing to do is to get the car up on a jack and shake the wheels looking for ball joint, bushing, or strut problems.

 

[James Downing]

For some reason, the most logical, in my mind is that the strut bearings are going somewhat bad, or showing wear. I have noticed my passanger strut (I think) is ticking when I turn the wheel at low speeds. So, maybe the drivers side is going bad along with it. They are still the stock struts and shocks. Maybe its time for new ones.

Any other ideas out there?