Audi A6 + RS6 (1997 - 2004) - 1998 2.5tdi Quattro tiptronic - Gearbox

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Wed 16 Jul 2008 18:33
1998 2.5tdi Quattro tiptronic - Gearbox - mjple
Ok so having had an A6 1.9tdi previously which I loved, I decided to treat myself to a low mileage upgrade. It was pretty cheap, had massive service history and in retrospect far to many gadgets to go wrong.

My last Audi never had any major problems despite getting to 185,000 miles and this one only had 64,000 when I got it. All has gone well until just recently at 77,000 miles.

I was on the motorway and decided to overtake someone, a car was coming in the fast lane but I knew the amount of power I had available to overtake. I put my footdown which took the 5 speed auto which was in 4th down to 3rd, the revs increased as I went past it got close to 4000rpm so some way off the redline when I felt like I was going to go through the windscreen, the power failed massively, I pressed harder on the accelerator and the car slowed even more causing a problem as the car behind me saw no brake lights and had no idea of the deceleration. In the end I let go of the accelerator the car jumped up into 4th and away I went.

I tried this again the next day and noticed that when I get to 4000rpm there is a loss of power, if I keep my foot down on the accelerator the rpms drop and the car slows down by a good 20mph and black smoke comes from the back of the car until i let go when the gear goes back up and all is normal. I have found it does this 2nd and 3rd, but have yet to see it in 1st. Dont know if it woudl do it in 4th as I would be going to fast to legally test it.

So do I have a dreaded autobox failure? But why 4000rpm? and why black smoke out the back? Or is it a diesel pump failure or could it be something as simple as a coked turbo? but then the turbo sounds great when revving in idle.

Finally, I noticed about a month ago that the cars mpg has dropped. Once when accelerating up a hill it would go no lower than 12-13 but now it drops to 8mpg.

Any help much appreciated, but please let it be good news. I really cant fork out £1500 for a new autobox.

Edited by Webmaster on 16/07/2008 at 19:03

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Wed 16 Jul 2008 18:49
1998 2.5 Audi a6 2.5tdi Quattro tiptronic - Gearbo - adverse camber
Doesnt sound like autobox to me. The revs dropping suggests engine problems.

Any strange noises?

Get the fault codes read and have a good look around all the hoses, I'd start with the intercooler and turbo hoses and valves.
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Fri 18 Jul 2008 18:32
1998 2.5 Audi a6 2.5tdi Quattro tiptronic - Gearbo - mjple
Thanks for the response. I noticed today that when at the lights I pulled away quickly to get in front of someone.

The revs went all the way up to about 4000 and then just as I felt the engine start to lose power the gear changed into second. The car then continued to make a lot of noise like it was accelerating but out the back a lot of black smoke was appearing the car was barely accelerating at all and the rpms were struggling to.
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