I purchased this car (2001 996 Tip) a few years ago with 87K miles on for R&D purposes to test exhaust components. It had a drivetrain noise that appeared at exactly 48mph and would go away by 50mph or so. It was a howling noise indicative of a bearing or such.
First thing done was replace the tires/wheels. No change.
We removed and replaced both rear bearings, no change.
Then moved to the differential. Changed the lube, no difference.
So then we removed and inspected the R&P, saw nothing wrong and no wear.
With all that checked out we moved to the transaxle and changed that fluid. No difference.
The option left was a bad tranny. So we bought a used one from a wrecked car and swapped it out.
You guessed it, no change.
So I threw my hands in the air and decided I'd just drive the dam thing until something lets loose, then by god I'll know what the problem is!
Well here we are 2+ years and several thousand miles later and no change!
I even drove the car one spring 1000 miles from AL to way up north and got caught in a snow storm!
Same deal, howls at 48-50mph, no other time.
I've really enjoyed the car and would like to get another one but with a manual trans, I just don't like the automatic which I bought so my wife could drive it. She doesn't drive it. Anyway I don't want to sell it with this rotten noise.
Here is the best detail I can give:
> Noise is louder when the weather is hot. Quiet in the wintertime.
> Noise is most loud in 4th gear, shift to 5th and not so loud.
> Does not do it all of the time but most of the time.
> Hit the throttle hard and shift through the gears and it acts perfect. No noise, no nothing but crisp strong shifts.
> Shift manually while slowly accelerating and it sounds the worst at 48-50mph.
So I'm stumped. This is my first 996 and I know zero about them. I'm an air cooled guy and know quite a bit about those cars.
Anybody have any idea what this could be?
