maranelloboy05

Im officially out of ideas, I've got a whirring noise that increases with speed that I can't figure out. I hear it from the left rear of the car, but passengers say it's from the middle or right rear.

It's very noticeable around 16-17mph, 34-37mph, 42mph and 65+. At 80 it is very loud. At 70ish I can just about hear it with the top down.

Ive swapped the diff which made no difference.
Theres no play in the wheel bearings.
Directional change seems to make no difference.

Any ideas?

Slowcrash_101

Transmission output shaft bearing? Not sure if you already changed that.

maranelloboy05

I thought those were only an issue with the AP1 trans, have you heard of any AP2 failures?

Just to add, no driving seems to have effect on it, clutch in or out, changing lanes, gear, accel, deccel etc. The pitch increases with speed this accel, but nothing else changes it. I think I might have both rear wheel bearings replaced as a next step, I just hate to continue throwing money at something that no one is 100% sure of.

Car Analogy

Can you try to reproduce on a lift? Driving on the lift, see if it still makes noise with no road force.

If it doesn't, that is an important clue.

If it does, can use mechanics stethoscope to pinpoint.

maranelloboy05

Might be able to find someone that could do it. That said from memory we ran the car through the gears after a clutch install and didn't hear anything abnormal.

afzan

Try a different set of wheels/tires

twohoos

My AP2 trans has the output shaft issue. On a good day it's not too bad; on a bad day it sounds like straight-cut gears.

Jack it up and have someone gently run it up to 3k or 4k in 3rd or 4th gear - it'll be obvious if the noise is coming from the trans.

maranelloboy05

So here's some thinking on my part leading me towards wheel bearings. This noise started when I lowered the car. At the same time I swapped the cups on the axles and I had assumed crappy grease was causing the noise. I swapped axles and its still present. I'm now wondering if lowering the car adjusted the axles enough to change how they contacted the wheel bearings. This weekend when I swapped the diff I added axle spacers and I will say I think the noise diminished slightly. Could the added pressure from the spacers have reduced the noise? I'm clearly not a mechanic so just curious if this line of thinking makes sense to anyone else?

maranelloboy05

I'm considering just having the wheel bearings swapped. I got a quote for $200 for replace both rear bearings or $115 to diagnose for the noise, figure I might as well just have the bearings replaced at that price. It would essentially confirm the trans to be at fault, everything else behind the driveshaft has been swapped.

Slowcrash_101

It's going to cost a little more to do the wheel bearings. Even if you cheap out on parts, it's going to be ~$120 for new hubs and bearings. So unless they can pull both knuckles install the bearings and hubs, and slap it all back together in an hour or less expect to pay a little more. I'm not the fastest guy, but it would take me at least 2 hours to do the job.

Removing the axle nut, removing caliper and rotor, popping the ball joints off, pressing out the old hub and bearing, pressing in new hub and bearing, then replacing the the knuckle with the new bearing and hub, and properly torquing down the axle nut, all that is at least 45 minutes, and you have to do it twice.