2004 C4S - told I have bad transfer case - IDEAS

New member here in northern Ohio. Recent purchase of 2004 Carrera 4S Cab Tiptronic. Gorgeous ride. Runs well. Doesn't leak a drop of oil. 75k. Bought at good price knowing there was an undiagnosed differential "whine" coming from right rear. An Indy I trust says he thought it was just the differential, however he now tells me it's the transfer case and AWD not working as it should. Quite a noticeable whine, a bit like a manual transmission in an old muscle car. Transmission fine, thought it was differential only (not too bad) but transfer case bad mumbo jumbo if it means a tiptronic replacement. Porsche will not sell him transfer case alone. They offered a rebuilt tiptronic with transfer case for $18,500. (absurd) He is looking used, etc and we will see what turns up. Questions are these: 1) Is this common for the transfer case to give up the ghost? 2) true that Porsche won't sell transfer case alone? 3) If I just go ahead and drive it like this what is the potential outcome? 4) what kind of labor are we talking here in addition to an engine drop? NO I didn't have it checked out first. And yes, I knew there was some kind of an issue there. DOHHHH This took bad turn, but that is life. Want to keep car. Just looking for some advice on direction and possibilities? - Hutch

I don't have the answer but the car looks VERY nice, as does your fairway behind it. Best of luck!

porsche does not sell separately....they recommend a full replacement. Not sure what going rate is. there has been quite a few cases with the 996 turbo tips...assumption has been the tranny mount. I bet your tranny mount is shot....causing excessive movement wearing down that gasket. there is one company that i know of in the states that sell the gasket...it's about 100 buck iirc and a couple hours labor with tranny in the car...no need to drop. I can't remember the company...it's in CT i believe...a well known tranny company. search the 996 turbo forum

sorry, it wears down the gasket at the tranfercase/tranny junction causing leak...then whine

I'm thinking C2S

Transfer case? AFAIK the AWD system in the C4 doesn't have a transfer case. The drive for the front diff comes out the front (back?) of the transmission. There is a viscous fluid coupling that is best I can describe it part of the front diff. I'm always a bit leery when an indy diagnoses a problem with a part that isn't in the car. Front diffs can be had. This includes the viscous drive. I can't recall the price. Sometimes you can find then used. Some owners remove the front diff and axle shafts and convert their AWD car to just RWD and put the hardware up for sale. The transmission/diff is rebuildable, if this is where the noise is coming from. When I had my 996 Turbo in -- which has nearly the same AWD system as your car -- and a leaking transmission (selector shaft) was found and there was some back and forth between the dealer and the factory about fix or replace, the techs told me they could rebuild the tranny. They said they can rebuild the trannies in the NA 996 models and while the two transmissions are not the same they car close enough. My point is the techs seemed quite comfortable with the NA transmissions so there's that. Cost might be a bit high. Curious as to what the cost would be I was "quoted" maybe $6K to fix the tranny including removal, repair, and installation. Fortunately the car was under CPO warranty and the old transmission was removed and a new one installed at no cost to me. There are a number of businesses that rebuild these transmissions/diffs, too. I can't recommend any but the names pop up here once in a while. Check the ads in Excellence and Panorama for businesses that rebuild 996 transmissions.

I had the front differential rebuilt including a new viscous coupling in my 996 C4S. It was roughly $3,500. It also began to display a subtle gear whine before it failed.

In the Tip at the tail end of the box there is a removable housing containing a couple of bearings and a gear which Porsche have named "the AWD output mechanism", anyone else would call this the transfer case. I wouldn't see it as a big issue to change the 2 bearings in it.

Call Gbox in Boulder Colorado. They may be able to help and give you a quote for a rebuild. (Not sure if they work on manuals only)

Make sure the tire diameter of the aftermarket wheels is within OEM spec. Otherwise, I have a 2WD conversion available.

If it's the front differential, as a couple have suggested, one possible solution is to remove that sucker entirely. This requires either acquiring a couple of axle stubs or dissecting the CV joint to remove the axle stub (I did the latter), but otherwise costs nothing. Obviously if you're trying to keep your car in concours condition/like-new, removing the front wheel drive components may sound barbaric - but it's easy and the result is enjoyable. And did I mention it's free?

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Quite a long way from the front diff....

Thank you all who have responded! What a great forum. It's very helpful. I'm leaving town for 10 days not sure what to tell the Indy. Will likely have to wait until I return. Porsche is telling him "New/rebuilt tranny only" or problems will surface. He is perfectly OK with a GOOD used tranny. Previous owner did have a leak in area of transfer case/AWD output case, in 2011. Repaired and doesn't leak a drop now. Likely damage was done then. Who knows what damage may have occurred if leak was long lived. What is the worst case scenario if I keep driving it like this while we find a good used 996 AWD Tiptronic tranny, rather than taking whatever we find right now? - Hutch

It's hard to guess about what COULD go wrong if you do nothing, since it has yet to be determined what exactly is making noise. Indy first mentioned right rear, but then mentioned AWD not working correctly. I guess I'd ask him to clarify what he means by "transfer case."

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If you have the $$$, bite the bullet and fix it. Hopefully, you can find a good, used complete case for a decent price. If not, sell the car. P.S. Hopelly your purchase price was LOW enough to have given you a cushion for this bad outcome

Change it to 2wd and see if the noise persists. If it does you know it's not in the pinion gears in front diff but could still be the spider gears and/or bearings... if the noise goes away you know it's in the front diff or possibly the output shaft bearing in the 'trasfer case'. Either way... just make it 2wd if you want for awhile and worry about fixing it later. That's what I'd do anyway.

Perhaps this is a totally uniformed remark, but the whining sound I am hearing is clearly coming from the right rear. I have several comments regarding nixing the AWD (front diff) but original post did mention the sound comes from the rear, not front. Is it still possible there is a front diff problem? - HUTCH (OP)

Has the right rear wheel bearing been eliminated as the source of the whine?

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YEP

When my front differential failed, it was difficult to determine the source of the whine initially. As it became louder and more frequent, I noticed that it was coming from the front of the vehicle.

I have a replacement transaxle for your car with 37K miles on it.. Its a tiptronic as well! I bought the car it came from to get the engine core. Contact me! A smoking deal awaits you, as I have had this for 3 years with no use for it!

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If the vicious coupler is making noise, then it would come from the right rear if you're sitting in the driver's seat. If you want to test if it's the AWD, remove the driveshaft (leave the carrier/front diff in place). If the noise goes away, then your most cost effective method is to do a full 2WD conversion, which is a helluva lot cheaper than a new trans.

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That's a good option too.

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Its such low mileage that its not even dirty! Its just sitting in my storage are collecting dust.

You need to find a shop that uses a tool like this: Amazon.com: STEELMAN 97202 Wireless ChassisEAR Diagnostic Device Kit: Automotive Amazon.com: STEELMAN 97202 Wireless ChassisEAR Diagnostic Device Kit: Automotive All they need is to clip one sender at each corner of the car and drive the car. Then they can pinpoint exactly where the whining is coming from. Other than relying on hearing it inside the cabin. Better to have it correctly diagnosed before shelling out $$$ and replacing the wrong parts.