Simon Barber

I have a 1997 A6, 2.8 Quattro Wagon. It's got the ZF 4HP18 4 speed auto tranny with no torque converter lock-up. Hence there is always some slip. I'm seeing 13% slip at 65mph. (3000 rpm instead of 2650 rpm calculated from tire size/gear ratios). Is this normal or high? (105,000 miles on this tranny). Can anyone else post their RPMs @ 65mph? (With standard size tires).

Simon

A6Gary

Your C4 A6 is equipped with an electronic differential lock (EDL) that minimizes slippage of the automatic tranny. Unless you have calibrated equipment (e.g. speedometer, tachcometer, etc.), you really can't accurately calculate the actual slippage of the driveline.

Simon Barber

The EDL is not a locker at all - the car automatically applies the brakes on one wheel when it spins, in order to divert traction to the other wheel.

Searcher

3000 at 65 is about what my A6Q runs so I'd say yours is normal.

As for converter lockup, I think it's fairly apparent that it "locks" the converter with the Third gear upshift, much like the Ford AOD does, which is why Third really lets you know it's there.