My 1997 A8 Quattro was doing just fine at 122,000 miles. I was fat, dumb, and happy that I didn't have the transmission problems I have read about for the past two years. However, yesterday in sub-zero weather, my transmission decided to go into limp-home mode on my commute to work. Long story short, my A8 is now a giant paperweight, unable to move forward or reverse. My local mechanic has picked up codes P0740 (Torque Converter Clutch Circuit Malfunction) and P0730 (Gear Incorrect Ratio). His opinion is that the transmission is kaput, and it's time for a new one. Your thoughts? Any recommended sources for a rebuilt transmission with warranty? Thanks.

 

Forward/reverse don't fail at the same time. I would check the fluid level first. Check your coolant too. Clear the codes and try to drive it again.

 

the second code probably a result of the first
Check fuses relays
Treat the beast to a trans flush and fluid level check -clear codes then if no go follow this with a tech that cares-seems a big assumption that the trans is kaput given this info.
the real meaning is he doesnt know where to start.
Find a good trans specailist and provide him with detailed diagnosis info.
If more from manuals is required please email me
Output on printer
Possible cause of fault
How to rectify fault
17114 P0730
Gear/ratio monitoring

Wrong ratio

- Gearbox output speed sender -G195 faulty
- Rectify fault as described under fault code 17105 / P0721

- ATF-level not OK or ATF contaminated
- Check ATF level

- Clutch slipping/defective
- or solenoid valve dirty/defective
- Check ATF for contamination

Notes re fault recognition for fault code 17114 / P0730:

? The gear monitoring system in the gearbox control unit checks the ratios by comparing the engine output and gearbox output speeds for whichever gear is engaged. The above fault code is displayed if an incorrect gear ratio (implausible signal) is detected.
? When testing the stall speed, the gearbox input speed in the torque converter should be approximately 0 rpm with the vehicle stationary and a gear engaged. If this is not the case, the above fault code will be displayed to indicate possible clutch damage (see "Reading measured value block" =>Page 01-115; Display Group 001
17105 P0721


Sensor for Gear output speed -G195


Implausible signal
- Open circuit or short circuit to earth or positive
- Check wiring and connectors according to current flow diagram 5)



- Screening for -G195 defective
- Gearbox output speed sender -G195defective
- Read measured value block =>Page


Continued ?

 

Thanks -- I will pass along this info and post the results.

 

I mis-reported one of the fault codes for the transmission -- instead of P0740, it should be P0741 (Torque Converter Clutch Circuit Performance or Stuck Off), in addition to the previously-reported P0721 (Gear Incorrect Ratio). Don't know if it makes a difference. My mechanic is dropping the pan this morning and replacing fluid and filter. He's also checking fuses, sensor connections and outputs, and relays to make sure we didn't get fooled by poor connections aggravated by the recent slush and ice buildup on the roads. We'll see what's next. I'm also looking for a reliable transmission shop in the Rochester, NY area. Thanks again.

 

Mine went into limp mode last week. It was about 10 below at the time. I debated what to do for 2 days and tried it again, and it worked fine. I had the transmission flushed and its been working good ever since.