Grinding noise when accelerating

[quattro004]

1996 A4 2.8l manual transmission with Quattro. 266k miles. Motor and trans are original. New fluid in transmission. Driveshaft and rear diff have maybe 150k on them. All axles are in good shape. Lately (before and still after trans fluid change) the car makes a grinding noise when accelerating in 2nd-5th gear. Not in first though. Imaging the noise of a bunch of rocks or metal shards in a rolling bucket. Im suspecting the drive shaft u joint and or cv joints as they have some play and there is residual grease spun around the underside of the car near them. Not super wet but you can tell some has gotten out. Any ideas on what this noise could be from?

[Wraith600]

Jack it up and inspect the shafts. When the boots go (as you can see evidence of it all over your rims) then water, dirt etc. gets in them and causes them to click, crunch etc. CV joints are the simple first step to inspect and check out. Do you hear the noise in one particular area of the car or all over it?

[quattro004]

I should have mentioned, I put it on ramps tonight and inspected each axle and the drive shaft. All axles and their boots are good. No leaks. All have been replaced at one point or another and most are relatively new. No obviously cracks or ripped boots on either CV joint on the drive shaft. U joint looks decent but it does have quite a bit of play in my opinion. Its not obvious if the noise is louder on one side or the other. It is pretty even which is why I am leaning towards the drift shaft, trans or diff.

[bryans12v]

Check out the wheel liners. If one has come loose could be rubbing your tire. Sound is similar.

[Cgoon009]

Or wheel bearings? I didn't notice mine until about 40mph

[woolveren]

My car had some grinding noise when accelerating, but it turned to be one of the pulley in front. I think it was the AC belt tensioner pulley..

[quattro004]

Or wheel bearings? I didn't notice mine until about 40mph

Wheel bearings actually seem pretty good. I've replaced the rears in the past but that seems like it would be more of a continual hum that changes when turning and I do not get those symptoms right now. I know the fronts could use a change eventually but I'm not sure if that is whats doing it right now.

[quattro004]

My car had some grinding noise when accelerating, but it turned to be one of the pulley in front. I think it was the AC belt tensioner pulley..

Interesting..My A/C is out right now but it might be as simple as the high pressure switch has gone bad. I'm planning on swapping the switch out for a new one soon to see if that will turn the compressor back on. With yours, did it make the noise in all gears? That's what has me puzzled is that there is no grinding noise throughout the entire rev range in first but its there in all other forward gears.

[woolveren]

With yours, did it make the noise in all gears? That's what has me puzzled is that there is no grinding noise throughout the entire rev range in first but its there in all other forward gears.

In my case, the grinding noise used to come at the high rev ends of 1st, 2nd and 3rd gear. It was not noticeable at 4th and 5th, maybe the increased engine speed/noise masked it at 4th and 5th gear.

If you are getting a continuous grinding noise, it might be something else like a wheel bearing/axle..

[quattro004]

I see. For me, the noise only occurs in 2nd, 3rd, 4th, and 5th and only while accelerating. The moment I let off the gas or depress the clutch it disappears which makes me think it is not a wheel bearing. Thanks for the input.