Transmission Behavior Question

[PixieVC]

All of you with RS6s... answer me this...

Under light acceleration (slow - gain of 5mph per 10 seconds), at what RPMs/Speed does your car shift from 2nd to 3rd, and 3rd to 4th?

The reason I ask - I've noticed that my car simply will not shift from 2nd to 3rd at any less than 25 MPH, under any circumstances unless I override the computer with the upshift paddle...

The exact same thing happens from 3rd to 4th, which it won't shift to at less than 40 MPH.

I'm just curious of it's normal... there are a lot of 25 MPH and 35 MPH speed limits around, and driving 38 mph at 2,900 RPM is going to be a whole lot more inefficient than 39 mph at 1,900 RPM. I'm regularly overriding the computer to force a shift.

I suppose my question is... is this NORMAL behavior for an RS6 trans? If it is not normal, what might be causing this behavior? And before anyone asks - shifts are always fairly smooth, very consistent, and predictable. Shift behavior under harder acceleration and wide open throttle is as expected - it will hold the gears longer, in the case of WOT, to redline and shift smoothly to the next gear.

Kickdowns and upshifts are also smooth. Torque converter works fine - very fast to lock, and I did the 'test' that some forum memeber suggested - 5th gear, 50 MPH, floor it... and the RPMs went up by about 50 (yes, fifty), and then back down to where they should have been in the span of about 1 second... so I'm guessing it's working as designed..

Any pointers? Am I just being a car hypochondriac? Thanks...

[peiserg]

just Vag your transmission. if there is an issue it will show up.

[PixieVC]

just Vag your transmission. if there is an issue it will show up.

I'd love to. Let me just conjure up the equipment and software and read the codes. Or maybe there's money in me developing a telepathic code reader for cars in general? A mind to computer interface for OBD-II... Or I know, I will let the mechanic I keep in my trunk do that for me and have him issue a full report. This would be an excellent use for an old middle east oil lamp.. Rub it and get 3 wishes...

point is: not all of us are so equipped. To get it scanned I need to go to a mechanic and shell out dollars - neither activity I enjoy much (who am I kidding? I LOVE spending money!!)...

[JSRS6]

Those are the normal speed shift points.

[mik15]

mine changes below what Pixie is describing here, it's shifting around 2200-2400rpm if i let her do its job and do not interfere, i am not sure if this matters, mine has an ABT tune but as i understood from them they didn't reprogram the TCU...

[MaxRS6]

I'd love to. Let me just conjure up the equipment and software and read the codes. Or maybe there's money in me developing a telepathic code reader for cars in general? A mind to computer interface for OBD-II... Or I know, I will let the mechanic I keep in my trunk do that for me and have him issue a full report. This would be an excellent use for an old middle east oil lamp.. Rub it and get 3 wishes...

point is: not all of us are so equipped. To get it scanned I need to go to a mechanic and shell out dollars - neither activity I enjoy much (who am I kidding? I LOVE spending money!!)...

Invest in the Ross-Tech cable. It is a "must-have" for any RS6 owner IMHO. For a few hundred dollars you can scan your own codes and it can provide a wealth of information. By pulling a "base" log of information, you will be able to view changes when performance issues arise or the dreaded CEL decides to rear its' ugly head. The information can also be very helpful when dealing with techs.

http://www.ross-tech.com/vag-com/index.html

If you don't yet have the MTM TCU chip- Get it.

[mik15]

Max - which one would you say is the best one to buy? i am interested in one! Is the KII-USB ok?

[aussie rs6]

+1 - get it from hoppen for ~$125. The minimum "must do" upgrade for any C5 RS6.

[kday]

I bought the HEX-CAN when I bought my RS6. It's more future-proof and I think there may be some upgrades (bluetooth?) that require the CAN part.

I agree it's a critical investment for an RS6 owner. I keep it and an old laptop in my trunk at all times.

[vitalian]

Pixie, although those shift points are just a tiny bit higher than on my car, they look pretty normal to me.

[peiserg]

Sorry for assuming things here.. but if as you stated when you got here, your goal is to beat the shit out of the car until it's basically only good for parts, one might assume you would have a $125 part that would save you the inevitable trips to pay someone to figure out whats going on. And as an aside, once you've done the whole beat the hell out of the car till it's only good for parts thing, can you save me some of your switches if they are still cosmetically and mechanically sound? The dealership wants a lot O' cash for the switches I need.



I'd love to. Let me just conjure up the equipment and software and read the codes. Or maybe there's money in me developing a telepathic code reader for cars in general? A mind to computer interface for OBD-II... Or I know, I will let the mechanic I keep in my trunk do that for me and have him issue a full report. This would be an excellent use for an old middle east oil lamp.. Rub it and get 3 wishes...

point is: not all of us are so equipped. To get it scanned I need to go to a mechanic and shell out dollars - neither activity I enjoy much (who am I kidding? I LOVE spending money!!)...

[PixieVC]

Oh boy. I knew taking certain liberties would come back to bite me. The car will be serviceable at the time I decide to let it go. I made a huge investment in the car, above the price of purchase, to ensure that it'll be working well for me for at least a few years. Per your comments, I've gone ahead and decided to dump the several hundreds of dollars on a computer interface for the car so I can... look at a stream of numbers and try to determine if there's a problem. Fortunately pattern recognition happens to be my personal piece de resistance as an engineer and analyst, so I should be able to have this figured out in no time.

MTM TCU, huh? I really don't want to rip up the carpet for that... anyone know of a shop or a man I can pay here in the SF Bay Area to handle these sorts of things for me? Doing the computer upgrades, for example...

[lswing]

Oh boy. I knew taking certain liberties would come back to bite me. The car will be serviceable at the time I decide to let it go. I made a huge investment in the car, above the price of purchase, to ensure that it'll be working well for me for at least a few years. Per your comments, I've gone ahead and decided to dump the several hundreds of dollars on a computer interface for the car so I can... look at a stream of numbers and try to determine if there's a problem. Fortunately pattern recognition happens to be my personal piece de resistance as an engineer and analyst, so I should be able to have this figured out in no time.

MTM TCU, huh? I really don't want to rip up the carpet for that... anyone know of a shop or a man I can pay here in the SF Bay Area to handle these sorts of things for me? Doing the computer upgrades, for example...

The codes read out really easy, interface is great, used it a few times to diagnose simple issues on my own, no trip too the shop. Also the TCU is pretty easy to get to, side board snaps off, carpet lifts up, 5 mins or less, plug and play if you send it to Hoppen, although they have a backlog I'm guessing. The shift points with my MTM go higher the further my foot is in the gas. Easy on the pedal and it shifts around 2,500-2,800, hard on the gas and it doesn't shift until 6,500:) And driving in Trip is ultra smooth if you shift right on, downshifts are amazingly smooth at a stop sign.

$250 for the RT cable is nothing, I'm looking at a $2k steering rack sometime this year...

[PixieVC]

The shift points with my MTM go higher the further my foot is in the gas. Easy on the pedal and it shifts around 2,500-2,800, hard on the gas and it doesn't shift until 6,500:)

Mine does this...

Perhaps I already have a TCU and don't know? And perhaps a chip. Given how badly I murdered my friend's E39 M5 the other day... there might be some merit to it.

[Hy Octane]

With the adaptive TCU shift points will change according to conditions. If I do a short trip on the freeway in D the tranny adapts to higher shift rpm.. when I return to traffic in the city.. at first it continues this pattern,.. over a period of a few minutes of being in slow n go traffic, the shift points come down until it will go into 5th gear at 35 mph.. so for me its a constant change deal.. I do wish there was a way to isolate the shift program that one prefers and have it as a default.. in other words, a way to switch off the adaptive brain when you have found the ideal program that suits your style..

[PixieVC]

With the adaptive TCU shift points will change according to conditions. If I do a short trip on the freeway in D the tranny adapts to higher shift rpm.. when I return to traffic in the city.. at first it continues this pattern,.. over a period of a few minutes of being in slow n go traffic, the shift points come down until it will go into 5th gear at 35 mph.. so for me its a constant change deal.. I do wish there was a way to isolate the shift program that one prefers and have it as a default.. in other words, a way to switch off the adaptive brain when you have found the ideal program that suits your style..

Are you modified in any way? Stock?

Mine is anything but adaptive. It's the same pattern regardless of driving conditions or circumstances... feels like an old analogue non-electronic gearbox. My trans will only adapt to higher, not lower shift points under harder acceleration.

My computer won't let me select 5th at less than 40 mph, and less than 35 mph will downshift into 3rd.

[Hy Octane]

Mine is stock.. you might try resetting the ECU/TCU.. not by Vag com but by physically removing one battery cable for a few minutes and then reconnecting it. You might have to reprogram a few things like radio and window codes, but it willreboot the computers on board and reset everything to default.
Like any computers, they get a bit confused sometimes and need a reboot..

[kday]

Disconnecting the battery won't reset everything like it did in the past. The ECU stores some things in a non-volatile EEPROM. I don't know about the TCU.

[peiserg]

The TCU is really a 1 banana job. Maybe even a 1/2 banana. It's under 5 minutes, and that's if you go slow. If you are an engineer, this would fall into the 1st semester, intro to freshman physics class.


Oh boy. I knew taking certain liberties would come back to bite me. The car will be serviceable at the time I decide to let it go. I made a huge investment in the car, above the price of purchase, to ensure that it'll be working well for me for at least a few years. Per your comments, I've gone ahead and decided to dump the several hundreds of dollars on a computer interface for the car so I can... look at a stream of numbers and try to determine if there's a problem. Fortunately pattern recognition happens to be my personal piece de resistance as an engineer and analyst, so I should be able to have this figured out in no time.

MTM TCU, huh? I really don't want to rip up the carpet for that... anyone know of a shop or a man I can pay here in the SF Bay Area to handle these sorts of things for me? Doing the computer upgrades, for example...

[4everRS]

Pixie, I have bad news for ya. You will be spending much more on this car as time goes on. I consider it a pretty high mainanence car when compared to normal cars. And even the regular maintenance is much more expensive than a normal car. You ought to have a couple thousand in savings just dedicated to car issues. That or the cash flow to be able to sustain a financial hit when something like the tranny shits the bed.

[PixieVC]

Pixie, I have bad news for ya. You will be spending much more on this car as time goes on. I consider it a pretty high mainanence car when compared to normal cars. And even the regular maintenance is much more expensive than a normal car. You ought to have a couple thousand in savings just dedicated to car issues. That or the cash flow to be able to sustain a financial hit when something like the tranny shits the bed.

I have a $5,000 slush fund for the car. I figure that should cover the bases for anything short of my engine blowing up...

[peiserg]

The $5k will hopefully hold it. Most of my servicing has been under that, but this last one was $7200, and the one before that was $9100, i believe. The last one was valve cover gasket, 4 injectors, temp sensor, timing belt, water pump and cv boot. can't recall the other. I think i blocked it out of my mind from the pain.

[hahnmgh63]

In my case KWV3's to replace the crappy recall DRC and the Revo / MTM software and that is it except engine, diff, and tranny oil changes and rotors which thankfully I do all myself. That is until, my own fault, I broke the downpipe stud not being careful enough trying to remove them to gut them. Now I dumped $8K into the car, tranny/TC, Turbo Rebuild, hoses, seals, all my labor. None of this had to be done I just figured while the engine is out make it all equal or better to new. Maybe my car was a midweek production and they weren't hungover on Monday or looking to get off work on Friday and didn't down too many liters at lunch while they put it together as it's been very reliable (I'm looking for something wood to knock on right now since I said that). I'm looking for another 5+ years of reliability with a trans that shifts better than stock.

[mik15]

since we're talking about money...only bought the car less than 3 weeks ago and already spent 5k and it's not yet as i want it to be but at least i did the important jobs like the DRC and T-belt so hopefully at least for a few months from now on i won't have to spend again too much money :)...hopefully!

[ttboost]

Disconnect both battery cables from the battery and touch them together for about 10 seconds. hen go drive it and see if it changes. Sounds like maybe your TCU is stock. The MTM TCU chip is a MUST for these cars. Not only will you get better shifts and drivability, you will prolong the life of your transmission (especially if you upgrade the TC too). Might cost a couple bucks, but will go long and far in helping you enjoy your RS6 experience....otherwise you will be in for a new transmission soon, especially if your ECU is flashed.

As I have said before... you REALLY have to love Audi's and love THIS car, to put up with some of its shortcomings...and if you can't wrench yourself, you will spend a decent amount paying someone else to...

[QuattroRS]

Yeeks, were these out of pocket service costs or extended warranty pick up the tab?

What switches do you need? I have stash.


The $5k will hopefully hold it. Most of my servicing has been under that, but this last one was $7200, and the one before that was $9100, i believe. The last one was valve cover gasket, 4 injectors, temp sensor, timing belt, water pump and cv boot. can't recall the other. I think i blocked it out of my mind from the pain.

[905084]

Pulled TCU and fairly easy to do with only 2 screws holding the kick plate, pulling up the plastic sill plate and prying up the carpet enough to pull the plastic TCU box. Take the plastic cover off and pull 2 more screws to get the aluminum TCU cover free. Connector is a cam over lock that rotates off. Now when I took the plastic cover off, the top of my TCU cover fell off. Apparently, it has been apart before as the tabs are all broken off. Can anyone look at the TCU board and tell me if it is stock or has a chip? The chip in the upper left has a label on it and doesn't appear to be a factory solder job. I pulled the TCU because of shift problems (coming out of gear under WOT).

12124

[kday]

905084, I don't know if you're chipped or not -- hopefully someone else will recognize that label -- but could you do me a favor while you have the TCU out? Assuming you have an meter that can measure resistance, otherwise never mind.

I am curious to know what the resistance is between the two CAN bus pins on the TCU. This can be done with the TCU on the bench and unpowered. The two pins are 85 and 86, which are most likely labeled on the connector with very small numbers.

[905084]

Sorry kday, just chucked it back in to take for a spin and see if the contact cleaning helps my shifting problems. I'm sure it will be out sometime i the near future though. What do those pins do? Don't want to ohm out something a fry a chip, but happy to help if I can.

[kday]

Those pins are the TCU interface to the powertrain CAN bus, which connects the ECU, TCU, ABS, steering angle sensor, instrument cluster, and (maybe) HVAC head. It's essentially a computer network, not that different from an Ethernet you might plug your PCs into, but optimized for reliable real time transfer of small pieces of data. In this case, things like engine speed, gear selection, etc. Instead of running discrete wires around the car carrying e.g. the tachometer signal, like in the old days, the ECU sends a data message periodically, and any interested control units will receive it.

At the electrical level, the bus is what is known as a transmission line, and one property of transmission lines is that they must be "terminated" at each end with a resistance, in order to prevent signals from being reflected from the ends of the bus. These reflections can corrupt data. I want to verify that the TCU is not terminating the bus. The Bentley manual suggests that it is not, but the Bentley has been wrong before. This is relevant for those of us looking to replace the automatic gearbox with a manual. If the TCU were terminating the bus, its removal could cause bus errors. And in fact there are CAN bus errors present in the 6 speed converted RS6 that I know of. This is a long shot but wouldn't it be funny if a resistor costing a fraction of a penny could fix those issues...

If the TCU is terminating the bus, there should be 120 ohms between pins 85 and 86. If not, the resistance will be much higher.

No worries if it's not conveniently accessible.

[905084]

The CAN bus must be like an Arinc 429 bus in aircraft I assume. I'll check it next time it's out. Had the beast out for a spin after contact cleaner on the TCU and it didn't miss a shift. Still had the MAF implausible signal and banks 1/2 running lean so it's time to find a leak i would guess.

[kday]

I wasn't familiar with ARINC 429 until I just looked it up on Wikipedia, but yes, it is very similar.

[4everRS]

905084, can't tell if your tcu is chipped. I doesn't look like it by the solder work. Looks original. I've been wrong before.