152MPH

Hey all,
I have a 97 A6 Quattro Avant and the transmission will not upshift into 4th gear. I bought it used 2 years ago and it has always been like this. It shifts smoothly and properly from R 1,2,3, but at 60mph you are pushing 3200rpm and they just keep climbing. The selector lights on the dash are burnt out, so I have to assume that it is not in 4th gear. The MIL light comes on and the car shows a code of P0734 and says "4th gear ratio incorrect" on my OBD2 scan tool. What do you think could be the root cause?

A6Gary

1. Check ATF level (clutches can slip when oil pressure is low).

2. Check connector to engine and TCM for contact corrosion, water penetration, and loose fit.

3. Faulty ECU or TCM.

4. Engine RPM signal faulty and not yet recognized by OBD as faulty. Read Measuring Value Block to determine if RPM is resgistering correctly.

5. Connected wire from engine to TCM loose faulty.

6. 8-point connector front, on tranny between valve body and wiring harness loose or faulty.

Have you trire manually shifting the tranny to verify that it doesn't go into 4th gear? BTW, you can find R&R instructions to fix your gear selector dash display lights in the C4 FAQs.

A6Gary

BTW, @ 60 MPH, you would be WAY above 3200 RPM in 3rd gear.

152MPH

Thanks for the help that gives me some things to start knocking down. I have changed the filter and fluid with oem parts and the reccomended german fluid, the old fluid was a little bit on the reddish brown side, but no real smell to it or burnt appearance. As far as the manual shifting, yes, if I get the car going up around 60mph, which does register 3200rpm on my tach,(not shure if this is normal on other audi's), moving the selector from (D) down to (3) produces no shift or change in rpm. That's precisely what gives me the impression that it's not shifting up to fourth. Also, when you accelerate from a stop you can watch the tach and notice the shift from first to second and then to third, and then all the way up to 85mph,(as fast as I ever drive the car), you never see the rpm's drop for a shift to fourth, just a constant rise to around 4100rpm at 85mph. My friend's V8 Quattro cruises at just over 3000rpm at 85mph if that's any comparison.

I really appreciate the help