wrinkledpants

I, too, am a Redline fan. Most of the well known gear oil companies (Redline, Amsoil, Motul) all make their gear oils synthetic. The factory fill for the whole driveline is non-synthetic. If you live where it's flat, you don't track your car, you don't tow, and you don't see cold winters - the factory stuff is just fine. It'll be more expensive than going with other fluids, though. Most of the good driveline fluids advertise to "meet the spec," but they don't all submit samples for licensing, and therefore don't show up on Porsche's approval list. It's not because the fluid is unapproved, but that the company didn't pay the fees for the testing and licensing. Sometimes - this is confusing for people.

I'm pretty sure the GTS doesn't have a locking rear diff. I think that only came on the off-road design package. But, you can check by going into low-gear, then locking the center diff, and flipping the switch one more time to see if the rear locks. Or, look at the rear diff. The stepper motor to lock it is on the driver side of the rear diff, and it's about the size of a soda can with a wiring harness plugged into it. You can't miss it.

For me - if the fluid meets the spec and it's from a reputable company - I wouldn't have a problem using it. Most report smoother shifts going to a synthetic, but that also could be from the fact that the old fluid was just that - old. Replacing it with OE fluid might have smoothed out the shifts just the same. Lots of people will have opinions on driveline fluids, but really the only sure-fire way to know is with an oil analysis. I don't see many of those on gear oils. For me personally, the only fluid I don't use that is approved is M1 0W40 because it will shear to a 30 weight. Lots of people with good UOA on that fluid, but also lots of them showing the shearing. This is why a number of drivers from various brands and models elect to not use M1, especially if they track or drive in a manor that puts their car through the paces. But - that's just my opinion and my personal choice. Not bagging on folks that choose to run that fluid.

No - just drive it. It's not hurting anything to start in first gear. How many miles on the car?

The idea of preventative maintenance is to replace before you get indications of failure, or at the very least, or a long ways from home with a check engine light. All the parts I listed - in total - might be $600. And, they'll all last another 10 years or 100K miles, if not more. For me - I much prefer to replace items when they're still good, but nearing the end of their life, rather than develop a coolant leak, run rich for 20K miles, or have some other problem develop. But, much of my maintenance ethos stems from the aviation world. YMMV

Turn key on (but don't start car). Push gas pedal to the floor and hold for at least 10 seconds. Release gas pedal, turn car off, pull key out of ignition. Restart car as normal and see if that does it. The tranny will learn your driving habits, and sometimes it's not always for the better. Depending on the mileage and age of your cayenne, you may be due for a fluid change, too.

On top of what you've listed, I'd do the coolant reservoir cap, coolant temp sensor, primary oxygens sensors, water pump, thermostat, power steering flush (and all fluids, actually). It's what I'll be doing and I'm at 100K miles. Most oxygen sensors start to decay and reach their life expectancy at 100K miles. They could go another 50K miles before throwing a code, but Bosch states that their usefulness is up around 100K miles, and it's what I've experienced on other cars. You could probably check your long term fuel trim numbers to check, but it's a wear item. So, do it now or do it later - you'll need to replace them at some point. I'd rather do it ahead of time before getting a misfire and having to start down a lengthy troubleshooting process.

I'm sure you could probably do a search and find the torque specs. But, as for the procedure - it's not hard and they shouldn't need any special guidance. It's 3 bolts plus the ball joint and it comes right out. You just want to make sure they don't torque the bolts back down until the car is resting on all 4-wheels, or they put a jack under the tire to get it into the correct position. But - this is how it should be done on any car.

Implausible signal usually means a dead or dying O2 sensor. Since the car runs in closed loop when it's warmed up and at part throttle, it'll try to maintain stoich using the O2 sensor as a feedback mechanism. If the O2 sensor was fine - then you'd likely see a rich or lean code if the injectors weren't doing their job.

The relay voltage and voltage at the injectors could be related, but not sure how. I'd start with swapping your bank 1 and bank 2 injectors to see if the problem follows. That would help rule out a bad injector(s) from a bad harness.

Misfires on Cyl 5-8 is a symptom of a problem. Could be an injector harness, or could be the failing O2 sensor.

If it were me, I'd start with getting the battery system checked to rule that out. It's like a poltergeist lives in the car when the battery is low. After that, i'd get a fresh set of primary O2 sensors in there. Realistically, they last 100K miles, especially on an FI car. They could go another 50K miles without throwing a code, but you'll be running really rich and well below what's considered "ideal conditions." Pull the harness off the ECU or disconnect the battery to reset the long term fuel trim data once the O2 sensors are in, and then drive the car for at least 50 miles if you restart the car and it's not misfiring. Rescan and see what comes back. If you're still misfiring on Bank 2, swap the injectors with the other side and see if the misfires follow. If they don't, then you know you have a harness problem on Bank 2. If you have a bad injector, you could probably get one at a salvage yard, pull the rest of your injectors, and send them for cleaning and flow testing (15 bucks an injector).

Honestly - I'd go back to the normal paper filter. The oil on the K&N filters can kill your MAF, and they just don't filter as well as the paper ones (demonstrated by a lot of oil analysis reports from various platforms). You gain almost zero HP with it, and given that you have a 5K+ lb car with a small V6, there isn't much you can do for HP mods that will make a real difference (that you actually feel). PAG and VAG cars don't usually have a flow problem when it comes to air boxes unless you're really going beyond stock HP. Lots of high HP cars from VAG and PAG running the OE airbox and paper filter. It's what I run on my CTT, and even when I get it tuned with a modified exhaust, I'll still run the stock air box and filter. Even if you could gain 5 HP from an air filter, we're talking about going from a power/weight ratio of .05 to .051. The Turbo has a power to weight ratio of .085. You're gaining 2% on your power to weight ratio. For comparison, the difference between a full and empty tank of gas is close to 3%. So, if you want a mod that doesn't add wear to your motor, drive around with less fuel.

My favorite mods are preventative maintenance. But, I think 20" wheels are kind of a sweet spot for wheels on this car. You can mount a 275/45/20 tire on there (stock size is 275/40/20) and that really opens up a lot of tire choices, plus it fills out the fenders nicely, IMO. I do like those wheels, and I have found that most replica wheels are pretty strong. So, I wouldn't worry too much about the manufacturer.

Not much else you can do with a V6 Cayenne. Stay on top of maintenance, and use that mod money for road trips.

Back tires on my CTT are a bit more worn than the front. Wondering if I should rotate them up front, or if they were possibly rotated to the rear before I purchased it, and I should just leave them until wear is even.

How do you know the whistling was from the turbos, and not an accessory bearing? Did you rev the motor and the whistling matches the spooling up and down of the turbos?

Good point. I'll just stick with OE and consider it a wear item. Doesn't look overly tough to replace, anyway. Thanks for the help.

Just reading about that now on the 996 forum. That's crazy. Does anyone make a metal water pump? Pelican lists 2 other manufacturers other than OE.

Don't have access to that magazine, but that's a bit starling about the pieces floating around in the system. If you do take the water pump out, find it's missing pieces, how do you go about getting them out of the system? Or is that something you just hope it comes out or hope it's not plugging an important passage? The blocked flow to a turbo wouldn't be good :(

When I get mine pulled up, I'll throw up some photos if it's missing pieces.

Makes sense. I guess I'll do the full monty, sans the Redline stuff. So, are you saying that the actual impeller will get smaller over time, and it's ability to move coolant is why people run into problems where they are over heating? I've never fully understood how a bad water pump causes an overheat problem if the impeller is still spinning at the same speeds. I get how the leaks form, and I guess I could see a leak introducing air into the system, but never got how the water pump itself caused an overheat issue - mechanically speaking.

Picked up an 04 CTT, and the PPI revealed that there is a small coolant leak on the coolant pipes (they are aluminum). Car has 100K miles on it. In previous cars, the water pump was kind of a wear item that was replaced at about 100K miles. I noticed yesterday (I'm in Denver), that the coolant needle would move beyond what's normal, and the fans seems to kick into stg 2 speeds, but it was only 60 degrees outside (slow speed driving in the city). I've read this is normal since the cayennes don't smooth the temp readings like many cars do, but was thinking about doing the Pelican Parts Water pump kit (water pump, thermostat, upper and lower rad hoses, reservoir cap, and some Redline treatment) since I'm going to have to dig into the back to fix the coolant leak, and also do the T-fittings while I'm in there. In my 88 911, it was really apparent that the thin Denver air made for a tough cooling situation since oil temps would rise and remain high, despite having an oil cooler and aftermarket high speed fan. But, in the thick California air, temps remained rock solid when the ambient temps were the same as Denver.

Does the water pump and thermostat cause people a lot of problems on higher mileage cars? I think I may do it anyway, but if people don't see many problems with these two parts (at any mileage), I may elect to not replace them.

Control unit is located under the right front seat.

The transfer case stepper can be purchased from VW for 382. Check VWparts2go for any 04-06 Touareg. I checked on my CTT and it's the same part number. The early versions of the stepper motor ended with an A part number (stamped on the motor itself), but the updated version ends with a C. I'm almost 100% positive everything behind the dash is the same part number (at least in regards to the HVAC unit) as the Touareg. VWparts2go has the cheapest new parts I've been able to find online (got most of my Touareg parts from them). When I cross checked a lot of the flapper solenoids with the VW part, it was quite a bit cheaper.