A8 2.8 Sport issues...!

[robmorphet]

Hi there all, never used this forum for posting, but has been great help with info in the past, so I thought I may as well ask you!

My 1999 A8 2.8 Sport facelift model has tiptronic problems. The gear and steering wheel shifter doesn't work - or rather doesn't select when moving. If I shift in to gear mode, say at 70/80mph it drops in to 4th, then 3rd, then sometimes 2nd!! Quite disturbing!! Other times nothing happens, the lights are on when I move the gear over, but nothing happens when I try and change gear. In auto its fine, and tows great (bike box trailer so not heavy).

The engine is sometimes very lumpy, when in gear and not moving, or rolling off from a standstill, almost jerking.

I know a little about cars, but tonnes about bikes - trouble is they don't have autoboxes so please help!!

Had the car 4 years, done 150K miles (mostly motorway) and do hammer it, but change the oil and filter every 10K.

Hope one of you guys can help me.

Rob.

[cruiser647]

Hi!

I think there are 3 things you can try - cheapest first:-

Change the spark plugs to new Bosch Super 4 jobs. (£60 max)

ssecondly:- Change the MAF (easy 5/10 min job) but it cost £100 - £200.

thirdly :- Get the gearbox fluid and filter changed. I think an Audi Stealer is best placed for this. This will cost about £100 - £200 as well.

Good luck!

[Chris_B]

Could it be as simple as a sticking selector switch? One of the steering wheel switches or gear level switches could be sticking and sending spurious signals to the gearbox to change down? If it works in automatic mode, there shoul dbe little wrong mechanically, and I doubt a transmission controller failure would only affect tip mode.

I can't tell you how to go about diagnosing it further though, but I'm sure somebody here will be able to give you some pointers.

[Botang]

Before spending any money or worrying unduely it would be best to have the fault codes checked to see if it bring up anything obvious, if you look in the Vag-com section of tyresmoke you will find a database of people that will help you out (just scroll down to U for UK listings). Either that or get yourself along to one of the Tyresmoke meets (see Meets and trackdays section) and ask if anyone can bring vag-com along.

As far as gear selection goes it does sound as though a switch or something like that is playing up, as Chris rightly says could be as simple as a dirty contact.

[PaulW]

Are you saying that when you shift from "D" to tiptronic, the gearbox changes gear without moving the shifter or steering wheel buttons?

If so, then it's either the switch on the shifter or one of the steering wheel buttons, or there is a short on the downshift leg of the electrical circuit.

To downshift (or upshift), there are two switches in parallel (one on the wheel, one on the shifter), when one closes, it shorts a pin of the transmission control unit (TCU) to ground. The diagram below shows a car with only a tiptronic shifter, the steering wheel buttons would be in parallel with the shifter switches.

That's your problem, this circuit is getting grounded out either by a sticking switch or a bad ground circuit.

Here is a diagram of the tip circuit:

So you'll have to troubleshot that, shouldn't be too hard.

The 97 A8 that came to the states did not have tiptronic, here is a procedure on how to retrofit it, click it and you'll probably find everything you'll need.

http://www.audipages.com/Tech_Articles/auto_transmission/97tiptronicupgrade.html

Good luck!

[robmorphet]

Thats great guys, thanks.

I'll change the plugs now as have used NGK ones, ref the gearbox change, is that a hard job? has anyone completed it recently? Coming from a bike racing background I change oil in the box on two wheels regular, would imagine it can't do any harm to drop the oil from an auto could it?