tanya_charbury

When I started this thread, I was planning to start an informal matchmaking thing focused on these C5 Audi A6 Quattro 4.2 V8 cars, not listing them but saying "there's one, go get it."

I'm clear the forum disallow members from listing cars they do not personally own. With that in mind, I was hoping I was coloring safely inside the lines based on what it means "to list"

Even so, a similar thread on the A8 forum was moved to "Vehicles for sale" which basically means "death by obscurity. I'm trying to avoid this thread here suffering the same fate. So, I've changed the premise of this thread. I am no longer planning to point to any more cheap, almost dead-Audis out there. Even so, I hope YOU find them and buy them.

As to what you're likely to find, here's some context based on a horribly-cynical timeline generalization:

• First owner: Someone originally bought the C5 Audi A6 Quattro 4.2 V8 for a lot of money new, and he paid the dealer to maintain it nicely. However, then he sells it. Why? Because the guy who can pay new-Audi money doesn't wanna deal with the anticipated unreliability. Maybe there's nothing wrong yet but he doesn't want his trophy wife to have to call a tow truck and miss her eyelashes appointment so he sells it preemptively because it's already about ten years old, so things are bound to start failing sooner or later. Besides, she'd love to have a new one because the new one has a cool new Bluetooth feature and a back-up camera like the Mercedes-Benz SUV her friend Liz drives.
• Second owner: The Audi gets sold to someone who starts out bravely and tries to go the dealer route, by which a ZF transmission filter will cost him $166 (actual price from my personal experience though I didn't actually buy the part from my local Audi dealer, just did a price check). Directly from ZF, that identical filter is $35 or so (yes, really). The A/C compressor is expensive at the dealer but if you know which Denso part number to buy (and I do, feel free to ask), you can get it literally at Wal-Mart new for less than $250. The Audi's second owner doesn't know this, so he tries to stay afloat but it's like dog-paddling with too-heavy lead weights. Eventually, he either drowns or cuts them loose. So, he sells the Audi, rationalizing that all the money he spent kinda sorta isn't really all that much, compared to what a new-car payment would have been.
• The third-tier owner doesn't understand these cars and there's a high probability that his wife chews gum with her mouth open. But, wow, an Audi. So he buys it. He doesn't even pretend to go the dealer route. Hello, Autozone and the local service station on the corner. Imagine the worst nightmare August Horch could have: this is it. The car's fine engineering is trashed by someone whose mechanic skills consist mainly of claimed superiority through condescension. By denigrating the Audi, the mechanic intimidates the owner enough to choose him. The monologue might include that these cars are so fulla newfangled crap, most of this stuff is unnecessary and those gawdamm Germans make everythang so fornicating complicated and Oddies especially ... but no worries, buddy, I'll take care of it. The owner has a bad feeling about all this but he doesn't know what else to do anyway. Besides, he feels strangely owned in a sort of Alpha wolf dynamic so he doesn't feel like he can talk to the mechanic as his peer. He slinks away and hopes for the best. Pretty soon the car won't run at all any more. The mechanic is unusually truthful when the last thing he says is: "hey buddy, I don't know what to tell ya." That's the end of the cash drain, except for maybe one last tow truck session. The owner lets the Audi sits on the street outside his apartment building until the battery is dead and his wife badgers him long enough. Maybe he adds in a couple of jump starts that do or don't fry anything, and then he advertises it on Craigslist for $1,000 or so.
• These are the cars that I buy, perhaps with the brakes so bad the wheel won't even rotate any more, or bright red transmission fluid, or totally mismatched, stripped, missing or overtightened transmission pan bolts, or the engine speed sensor wires having been cut and reconnected the wrong way, or the engine speed sensor having been removed and reinstalled with the spacer missing so it hits the flywheel, or the outer tie rod end so loose that the car does a slalom even while I hold the steering wheel steady, or only one large bolt is still present, to hold the sub-frame in position ... all actual examples from the cars I bought.

I have a friend who has 37 cats. I understand why she rescues them. The same mindset inspires me to rescue C5 Audi A6 4.2 V8 cars. I've bought eight so far, as I recall. I bought a blue one as a present for my mom. I alternate between driving a black one and a silver one. And, as I recall, I have five more. I have overdraft fees in my bank account almost every week and I'm avoiding eye contact with the landlady due to all the dead Audis parked around my place. Even so, I keep finding more. I *have* to stop buying them. But, you don't.

If we don't buy these cars, they end up at Pick N Pull and that's like seeing Marilyn Monroe, no longer in her prime, selling unsafe sexual services for $20 in an alley. There's just something sacrilegious about the whole thing. It bothers me.

However, I'm no altruist. I do intend that there is a "win" in here for me too, because I own and manage a used parts company (Old Car Life Extension Systems, Inc.) that's a paid vendor on this site, and although I have yet to earn my first dollar on Audis, we do make some money on BMW and Mercedes-Benz used parts. I'm hoping that if you get steal-of-a-deal C5 Audi A6 4.2 V8 cars going cheap, you might well also consider buying the used parts from my OCLES company especially if it's the transmission.

The more C5 Audi A6 4.2 V8 cars are on the road and the more helpful I am, the more likely you are to buy used parts from my company.

~Tanya

tanya_charbury

Here's an article I wrote for my classic car appreciation website, but perhaps the pictures below are more interesting. Even so, the article provides context ... aside from ending a sentence on a preposition, and if you see flaws then PLEASE point them out to me.

Bottom line, if you already own a V6 model, or you don't own an A6 yet, why might you choose to buy a 4.2 V8 model?

* * *

The 1999-2004 Audi A6 Quattro 4.2 V8 is the synthesis of two models, so a discussion of this model should begin with a re-cap of these.

1997-1999 Audi A8 Quattro

The 1997 to 1999 Audi A8 Quattro was the most upscale vehicle that Audi built at the time. It was a long, exceptionally wide vehicle, aesthetically elegant, and with the typical German luxury car features that put it on a par with the best that BMW and Mercedes-Benz had to offer at the time. It had some unusual features that made it hard to compete with:

• A magnificent engine, a modified version of which would later power a Lamborghini and the Audi R8 supercar: it was a 4.2 liter dual overhead quad-camshaft V8 with variable camshaft timing, variable-length intake runners, and an optimal combination of timing chains and belts. It was immensely strong yet light due having an aluminum block and aluminum cylinder heads, yet a forged crankshaft.
• A body shell, hood, trunk and doors made entirely from aluminum, making for a very strong yet light vehicle.
• A highly advanced all-wheel-drive mechanism called “quattro” that used the advanced low-friction and long-lasting torque-sensing differential popularized as “Torsen.”
• A magnificent and immensely strong 5-speed electronically controlled automatic transmission nicknamed Tiptronic, designed by Porsche and built by the German transmission specialist company ZF. Unlike historic automatic transmissions, this transmission enabled the car to accelerate even while upshifting, plus it had a manual-shift sport mode, plus a torque converter lock-up clutch that eliminated friction and heat in the torque converter, thus enabling fuel consumption on a par with manual transmissions.

1997-1999 Audi A6 Quattro

In the same time frame, Audi also sold the mid-sized Audi A6 Quattro, a competent and elegant design that was a continuation of the Audi 100 mid-sized 4-door sedan, albeit with the highly advance “quattro” and “Torsen” all-wheel drive.

The Pontiac GTO, and the Audi GTO

In the early 1960s, John Z Delorean was in charge of the Pontiac division of General Motors. At the time, Pontiac had no performance image. It made several large cars with large V8 engines, and it also made the mid-sized Pontiac Tempest. Into this, Delorean shoe-horned a massive V8 from a much larger car, and added various performance upgrades. He called the result the Pontiac GTO. It was an instant hit with the buying public. It also dramatically changed Pontiac’s image and became a legend.

Arguably, that’s what Audi did in 1999. It beefed up the V8 engine some more, upgrading it from a high-performance 32-valve engine to an even-more-powerful 40-valve engine. Then, it made the nose of the Audi A6 Quattro subtly longer and more square-shaped in front, to be able to accept the massive V8. The result was the Audi A6 Quattro 4.2 V8.

For its time, this car was exceptionally elegant, comfortable, advanced -- and with some many of its body panels being made of aluminum and its 300 horsepower engine, it was quick in an impressive smooth way. Its transmission was very strong mechanically.

The ultra-high-performance version of the same basic A6 uses the same basic engine and transmission but with twin turbo-chargers added, so as to generate 450 horsepower.

Audi A6 Quattro: The 4.2 V8 vs. the 2.7 BiTurbo

Here are two pictures I took outside my shop. Both cars are silver 2000 Audi A6 Quattro cars, the 4.2 V8 on the right and the 2.7 BiTurbo on the left. Please notice the front parts in detail (and please ignore that the 2.7 has an internally broken headlamp, and the 4.2 has cloudy headlamp lenses). Almost every front body part on the 4.2 is different, though subtly so, so that the 4.2 nose didn't look coffin-shaped aesthetically, in order to make the large engine fit.






I used to own both of these cars. They are pretty much equally fast, but I found the complexity of the 2.7 both impressive and overwhelming, so I sold that car to my fearless tech.

Here is an Edmunds road test comparing these two models of cars.

The main reason to avoid the 4.2 V8 used to be the transmission but I'm spreading the word that the single most likely point of failure can be prevented with a new pressure regulator from the ZF Distributor. I plan to elaborate on that in a separate post. I also have a renewed pressure regulator in my black 2000 Audi A6 Quattro 4.2 V8 and I'm driving it hard, revving it high, long distances, up and down the Sierras, runs from Reno to Vegas to LA to Sacramento to Reno, with documentation from the Nevada Highway Patrol proving I don't drive slowly. No transmission failures so far in 7,000 miles of such driving.

mytsigns

The 2000 A6 4.2 was the most beautiful and wonderful car I've ever owned. Bought off of a 3 year lease, the dealer (Buick) didn't know what he was selling. Fast! Fender flares! Unskiddable (if that's a word). Black on black, the perfect sleeper. How I cried the day the tranny died.

Please post your transmission maintenance schedule.

I love the idea of this thread.

tanya_charbury

@mytsigns Thank you for the encouragement!

Your black on black Audi sounds deliciously sinister. The interior color on mine is melange, which makes it a lot more bland.

"Unskiddable" is hereby a word. :-) I lent my tech one of my Quattro cars last winter (lots of snow and ice near where he lives) so he found an empty commercial parking lot and wanted to enjoy 300 horsepower while drifting. He came back looking a peculiar mixture of disappointed and impressed because the car wouldn't break loose. Now he wants to borrow one to enter in the upcoming Virginia City hill-climb near here, which should be an interesting test for the transmission (and driver, and hopefully not the air bag system).

One day in the distant future I plan to start leasing these 4.2 V8 cars out on the premise that people love driving them but are afraid of the maintenance. If my techs and parts stash are up to speed, it might be viable for me to offer a "lease it until something breaks and then bring it back and grab the next one out the pool" sort of deal. One day ... some day.

I have today read an article on an investor's website explaining how some classic cars are good investments due to appreciation potential, so if I can get the word out that no, Achilles isn't vulnerable after we give him some Kevlar boots, then all might be well as to the appreciation path for the C5 A6 Quattro 4.2 V8.

tanya_charbury

Context & Credits

This is not THE WAY, this is merely one way -- my way. It's based on what I've learned based on 2 years' worth of taking some of these transmissions apart, reading about them, writing about them, photographing them, and analyzing them, plus asking much-more-savvy-than-I people as to their opinions, plus spending time studying the spare parts catalog, plus doing 4 of these preventative maintenance procedures so far, plus some plain transmission services, plus lots of test driving -- all focused on the ZF 5HP-24A type of transmission. Fun! :-)

Budget

Aside from tools, budget for $500 if you do the work yourself.

A semi-used, semi-rebuilt transmission from my company is $2,700 and then you still have to install it, so it's much better to prevent disaster. If you follow Craigslist ads, you'll see these cars often being sold dirt cheap because the transmission failed. The root cause of the most typical failure is a preventable problem, as I understand things. Not just will your Audi be likely to last longer but if you do sell it, then with this fix having been done its resale value might well be much higher.

As might be expected with a part that combines complex and sophisticated electronic, hydraulic and mechanical components, the transmission does fail after approximately 15 years, if no preventative maintenance is done.

The failure is essentially instantaneous. At some point, the hydraulic pressure regulator in the front lower valve body housing allows a high-pressure spike through. Think "irresistible force." This blows out the rim of the clutch "A" drum. This disables the "A" clutch.

When this happens. the transmission slips in every gear that uses the "A" clutch, i.e.. the first four gears. Fifth gear still works and the car shifts into an emergency mode that some informally call “limp home mode” as in, a dog limping home after being hurt.

The transmission control computer continually monitors input and output speeds and if these are not within an expected ratio, it means there's slippage, so the electronic control unit then alerts the driver with a reverse-video display of the gearshift position indicator display on the instrument panel. This intends to convey: “Something is seriously wrong with your transmission, so 5th gear is the only way you can move forward for now.” Right then the transmission will jarringly shift into 5th.

Assuming the debris from the destroyed clutch “A” drum stays put, or finds its way safely into the transmission filter and isn’t slowly damaging other components, the car can hypothetically be driven in this mode for long distance. One of our project cars has been driving with a damaged clutch “A” drum for 18 months or so. In this mode, acceleration is slow, and revving the engine when accelerating might slip and burn out another clutch, so patience is advised. As the car picks up speed, it behaves well enough and it’s possible to get a speeding ticket in this mode on every public highway in the US. Even so, failure of the "A" clutch is best avoided, hence this article.

Cautions from a Too-Hot Blonde

I'm happy to provide input for folks to use at their own risk. It's NOT risk-free. I managed to hurt myself pretty badly though. I hope you will not make the same mistake I did. I burned my arm on the passenger-side catalytic converter. I’d felt it hurting but I’d decided to tough it out and finish the procedure, and thereafter go soak my arm in the kitchen sink filled with cold water. This was a bad mistake. I had basically slow-cooked my arm. The tissue damage was pretty severe and I’d have been better off abandoning the procedure and starting over later, and attending to my burned arm immediately. Owee. So, be careful, and enjoy the information below -- some of it was earned the hard way. :-)

Big Picture

The work is basically a combination of a transmission service plus renewing the hydraulic pressure regulator in the lower front valve body housing.

Pressure Regulator Renewal

As I understand things, that regulator is basically a light-alloy piston sliding back and forth inside a tunnel, so over 15 years, the piston and the tunnel wear each other out. There are various fixes to this, from too-informal-by-my-standards to way-too-complex-for-me-DYI to my preferred approach of sending the entire lower front valve body housing to Eriksson Industries, the ZF distributor in Connecticut, and paying them to renew the regulator. They are super-nice.

They bore the tunnel larger and install an oversized unit made by Sonnax, sort of like when you bore out your engine's cylinders and then install oversized pistons in your engine after the cylinders have worn so that they are no longer being smooth and round and the original size. In the process the ZF distributor folks also do some cleaning and inspection of the housing.

I send them many of these, so I get an unusual price but probably the retail price is still likely to be less than $300. I don't rush them so it takes maybe two to three weeks total turnaround time. If you take that route, during that time, your Audi is out of commission. It's also good to not have the pan off and risking contamination during that time, so it's not just a delay factor but also extra hassle (as in put the pan back on, and later take it back off again).

... and Now a Word from Our Sponsor

If you want to have only a few hours' worth of downtime for your Audi then first buy a core unit as to the lower front valve body housing, and then you send that to be renewed while meanwhile you're driving your Audi. My little company (Old Car Life Extension Systems, Inc.) will happily sell you such a core and buy your old core back later, with a $60 difference in the price, which covers the hassle factor and the risk involved with some of the cores coming back being unusable. So if you want to avoid a couple of weeks' downtime, and to that's worth $60 plus shipping, great.

You can probably get these cores elsewhere too but be careful to get a complete one so you don't have to assemble it when you get it back from the ZF distributor; there's a lot of spring-loaded stuff that can go flying across the room. That's why I like to get a complete one, send a complete one, and get a complete one back so I can simply pop it into my Audi.

If you buy the core from a not-so-savvy source, be discerning because there is an early version and a late version, and there IS an important-enough-to-matter difference. For the C5 A6 Quattro 4.2 V8 cars, you want the later ones, so either get it from another such car, or from a post-1999 A8 Quattro, NOT the 1997-1999 A8 Quattro because that's the early type.

Other Original ZF Stuff to Buy

While you're placing that order with the ZF distributor, also order from them an original-quality ZF pan gasket and original-quality ZF pan filter. There's a long story as to why. Now that I've learned enough, I choose the original ZF stuff for these two types of parts. Also order the little O-ring that goes around the upper neck of the filter. Also order a new ring to go around the fill plug.

Blauparts Stuff to Buy

Then, contact Blauparts. Buy a 6-pack plus one extra bottle of the special honey-colored transmission fluid that this transmission needs. They're nice people, and they'll also tempt you with their non-ZF gasket and filter. Politely resist -- but do buy the Blauparts hand pump too, and a weird little pipe that's shaped like a letter J so that it goes into the fill hole and then hooks on the side, so the fluid you pump goes up and sideways and down, so that it won't run back down unless it's for the right reason, which is the pan being nice and full of this fluid.

Tools to Buy

Get a pounds-inches torque wrench plus a foot-pounds unit. Get a bunch of Torx T-27 heads on various ratchets and a size that fits the torque wrench. Get the Ross-Tech VCDS software and the cable that connects a USB port in your Windows laptop to the ODB-II port in the driver footwell. Get a hex head (Allen-style) pair of wrenches that can fit the drain plug and fill plug, respectively and that can fit into the torque wrenches. I think they're sized 3 and 5 but don't quote me on that.

Safety Stuff

I bought a welder's jacket to protect my arm but you might not need it. Key point though is that you'll need to be under the car with the engine running, and also being nice and warm so that the transmission fluid is in the 30 to 50 degrees Celsius range, right as the transmission pan is so full that any additional fluid being added runs out the fill hole.

Gloves are very good. Eye protection is good but they make some things harder for me to see, which increases risk ... so I have mixed feelings about it.

Get some way of holding the car aloft sturdily and level, keeping in mind that the Audi jack is nicknamed "The Widowmaker." Also, the jack points and the bottom of the car nearby are not hard to dent and damage, if you put jacks or jackstands in the wrong places (as I found out the hard way). Even so, avoid jacking the car up using the rear differential since that can easily crack it. I like to use the body near the jack points but I use something to spread the load and not dig into the metal floor pan of the Audi. As you plan this part of the work, remember you'll be under the car with the engine running. Hot exhaust, hot fluid going up, hot fluid running back down your arm ... good times.

* * *

This pretty much covers the preparation. In another post I plan to cover what happens next.

~Tanya

clancy

Nice write up!

Are you familiar with the trans in the S6 with the V8? Is it safe to assume it has the same pressure regulator issues?

tanya_charbury

@clancy Thank you for the encouragement :-) I was inspired.

Yes, I'm familiar with the transmission in the S6 from studying the spare parts catalog. I'm undiagnosed as to Obsessive-Compulsive Disorder but it's a safe guess that I probably have it, so for me that means: I studied it in depth.

I also came sooooooooooo close to buying an S6 with a dead transmission but I was just too broke at the time, dangit.

The ZF 5HP-24A has more than a dozen sub-variations, with three of them pertaining to the A6 4.2 V8 and one to the S6. As I recall from reading the spare parts catalog, the main difference for the S6 variant is a different torque converter. Essentially and structurally though, the S6 variant is the same transmission as the A6. I can see no reason why the pressure regulator issues would be any different.

As I recall, the lower front valve body housing is not just similar in the S6 but actually identical, including the hydraulic pressure regulator. I'd want to check on that before I sell anyone a core on that premise, though.

~Tanya

tanya_charbury

I still don't have the remainder of the service plan documented but I've shown what I have written so far to one of the senior industry gurus, who has been kindly advising me and has personally rebuilt hundreds of these ZF 5HP-24A transmissions. He gave me the thumbs-up, so to speak.

Meanwhile, since I can't make case studies on this thread of Audi A6 Quattro 4.2 V8 cars that other people have for sale without it being considered a listing and hence a violation of the forum rules, I'll simply make case studies of the cars I've already bought - and truth be told, I'll probably keep buying more of them anyway. At these prices, e.g., $600 per car, I just can't say no. Worst case I'll run out of money and then I'll have ten Audis to live in. I'd be the classiest homeless lady, ever.

Meanwhile, to offset the reams of maybe-boring text I've been writing, here's a Nevada sunset picture of me from this evening with my black 2000 Audi A6 Quattro 4.2 V8, plus a picture of my Audi without me, plus a picture of me without my Audi. I'm sorry that latter picture is a little risque though it's nothing you can't see on any beach in America. It's the only closer-up picture from tonight where my face doesn't look totally goofy. From just the right angle, I can look okay.

4Driver4

Tanya,
This is both a bit of a thread jack and off topic, for which I apologize. I just swapped the failing trans in my D2 S8 with a spare I had, and I'm getting an intermittent code for the G93 temp sensor. Next time you have one of these C5 units apart, would you be so kind as to post a pick of the sensor? Thanks!

tanya_charbury

Let's consider my thread as exceptionally flexible plus you personally have extra credit due to all the helpful things you've posted. :-) So no apology needed, but thank you for being polite.

It's 4:30 a.m. and I'm still awake, so in case a quick reply helps you, here it is ...

As I recall it's a very non-dramatic part of the wiring harness; it almost looked to me like a bad spot in the wiring and then I looked it up some more somewhere and I realized "oh, that's the temperature sensor. It sure doesn't look like much, to me." I'm accustomed to sensors that are a discrete, noticeable electronic component and this temperature sensor, as I recall, was anything but. So if the premise of your question was "where IS the darn thing?" then maybe what I'm writing here is helpful.

From memory as I'm typing this, the thing is integral to the wiring harness that leads to the black-tower speed sensor and the solenoids, so if you swap the entire "inside the transmission" wiring harness, the temperature sensor will accompany the wiring. Unfortunately that still means dropping the pan etc. so it's no small task.

I've just revisited page 46 of the self-study program from Audi for this transmission, and their drawing of the sensor looks like it's a thicker part of the wiring almost like a low-profile inline old-school soldered resistor, the brown ones with the colored rings and a wire coming out each end, like my dad used to solder at the kitchen table. Even so, I somehow recall the sensor being more nondescript yet than the drawing.

Okay, I see the answer now. It's on page 54. The odd-shaped sensor is INSIDE a tube of sorts, the beige-colored one that sticks out out oddly from the otherwise neat-looking wiring harness. The first time I saw this, it looked to me almost like someone had messed with it and cut off something that was supposed to continue, but no ... that's how it's supposed to be.

I hope Audi doesn't mind that I took a screen shot and am attaching it to this post.




The manual also says "G93 receives a voltage signal from the TCM" so we probably shouldn't rule out that the sensor is fine but the wiring leading to it has been munched.

If you still would like me to also go take the pictures, please let me know. I'm being a bad engineer by giving you what I think you need instead of what you asked for, sorry.

At the risk of sounding like a mom: for the replacement transmission, have you renewed the hydraulic pressure regulator in the lower front valve body housing yet?

And also, if you live west of the Rockies or near OKC, I'd like to buy the failing transmission from you, please, if you're open to that. Which three-letter-code variant is that?

~Tanya