jfable

I just recently picked up a 2007 Turbo Tiptronic and have noticed a pretty distinct whine coming from the rear differential. The shop used a stethoscope and pinpointed that it was indeed the diff.

The whine comes when under very little load and is much louder at high speed. Off-throttle you notice very little and on throttle you notice very little. It's most prevalent with your foot just barely on the throttle.

I am under the impression that is is the gear 'lashing' that is creating the whine under those circumstances.

Is this normal for a 997.1 Tiptronic? I have read that our engines do have a distinct whine, but I'm not sure it is the same whine I am hearing.

Also curious about repair options if it's bad. Being a transaxle unit with the trans and diff in one housing am I looking at a full transmission replacement or can the diff be swapped on its own?

Thanks!
John

Quadcammer

Not really the diff, but the ring and pinion if I had to guess. not very familiar with the tip trans but I'd imagine you could remove the ring and pinion and look for damage or wear and then replace bearings or shims

Macster

Under what conditions was the noise pinpointed to be coming from the diff?

On some kind of roller dyno?

Or was the car on the lift?

If the car was on a lift with the engine running and the transmission in gear the axles droop and the CV joints do not like that much displacement. The transmission/diff noise emissions will be different that if the car is on the ground and the transmission/diff have to work against a load.

One has to be careful regarding noise. My 2003 Turbo started emitting a whine at speed that had me convinced a wheel bearing -- at least -- was going out. Backtracked 140 miles to the OK City Porsche dealer (the dealer nearest my location) and had the car checked out. Tech reported the noise was from the front tires. A slight misalignment. He had me feel the tire tread surfaces and sure enough I could detect the presence of feathering. Drove the car home -- almost 2K miles -- and once home had the car in for an alignment and after some more road time to give the tires time to adapt to the correct alignment the noise was gone.

If the noise is abnormal and if it is coming from the diff the diff and transmission are separate (the Tip and diff fluids are not compatible) so assuming the diff housing is unaffected by whatever is causing the noise the diff innards could be replaced and the diff resurrected.

jfable

Thanks for the replies!

Macster, it was up on a lift with the wheels drooping. What you said makes perfect sense.

The funny thing to me is the fact that it only is noticeable on slight load...there is no whine at all at high throttle or no throttle, and pretty much only noticeable over 60mph.

Since the car is new to me and I've never owed a 997 I think I am just going to not overthink it at this point. I'll listen every few hundred miles and make a decision if sounds start to change too much.

Also thanks for the note on being able to repair the diff. Looking at prices on transaxles had me bummed.

Thanks,
John

earossi

Is the whine gear or road speed related? If it is road speed, then I would suspect the ring and pinion. To replace the ring and pinion does not require that the transmission be disassembled; however, it will be an expensive repair. Ring and pinion gear sets are around $3000 plus the labor to install; so, I would expect the bill to be about $5.000. It may be more cost effective to search for a used transmission that is low mileage.

Kevin

I'd take your car into a Mercedes dealer and get a second opinion. The tippy was designed for MB. They can troubleshoot it as a 2nd opinion. If you need a R&P, I would take Ernie's recommendation to find a used box.

Macster

Noises are hard enough to diagnose when one is at the car. My best advice is to enlist the ears of an experienced Porsche tech. Let him road test the car. If he thinks the noise an issue then there you go.

I have to point out to new/first time owners these cars are a bit raw. They are luxury sports cars to be sure but the "sports" is a big part of the car. They are designed to handle well under even the most extreme conditions -- they are not race cars but are track tested.

Even my lowly base 2.7l 5-speed 2002 Boxster has a top speed (according to the factory) of 155mph. As a result the car is a bit raw because of the high performance tires, and stiffer suspension and springing to keep the car stable at high speeds under severe cornering. Not to mention the engine just inches behind the cabin with only a piece of carpeted sheet metal separating the engine and the cabin.

My Turbo is even more raw. I don't mind or pay much attention but people who ride in the car infrequently or for the first time always comment on the ride, the road noise, the ride stiffness, the exhaust noise, etc. Afterwards they comment on the performance and in a postive way. "Wow!" Or "Let's do that again!"

However, lest you get the wrong impression I admit I am pretty laid back when someone is in the car and don't go all clown crazy with car just to try to impress or show off.

Both of my cars manifest some transmission/diff noise. Remember in the case of my 996 Turbo and your 997 Turbo the engine is way in the back while the transmission/diff is pretty close to the cabin. In most cars the diff is way in the back under the trunk or located in the front and most (all) front wheel drive cars have tons of sound deadening to dampen the engine and transmission noise and keep it out of the cabin.

With the transmission and diff so close by I would be surprised to only hear a hint of tranny/diff noise.

But a Porsche tech can set your mind at ease regarding the noise. Either it is normal, or not, and if not then it becomes a question as to the source. I refer you to my previous post regarding tire noise having me suspect a bad wheel bearing so one can be fooled so the noise doesn't have to be transmission/diff related.

But if the noise is not normal and is with a very high confidence diagnosis deemed coming from the diff then at least you know and can decide what to do about it.

jfable

Thanks guys, I'll definitely get a second opinion. Although I think I am just being overly sensitive.

turbofever

are you running factory tire sizes.

CHECK!

Glennclifford

I have searched hi and low to find someone calling out similar symptoms. Did you ever resolve this?