2008 D3 A8 3.0 TDI Sport - Facelift - Revs hunting when cold - Torque Converter?

[cmarg]

Hi All,

having bought a 65k miles A8 last November (3.0TDI S-Tronic auto box), I was chuffed with it. I gave it a major service in May and also had gearbox oil & filter changed (expensive oil!). The car occasionally (when cold) would hunt revs by 50-100rpm when driving on the flat (with my housing development) at gentle acceleration at 20-30mph. Once warm this would stop. this happened both before and after the oil change

The problem got a little worse and I found gearchanges lumpy as well, as the hunting, there were occasional lumpy downshifts when going downhill (again cold) and backing off acceleration. At this stage I had my mechanic check codes and nothing showed up. He took apart the throttle body and cleaned it. However, the problem continued when I got the car back and a code eventually came up pointing towards the Air Inlet Manifold flap on Bank 2. I then swapped out both of these (on the basis that the other would go soon) and got the car back hoping all would be creamy smooth.

However, whilst the lump downhill changes and gone, the hunting is still there when cold, albeit not as bad. I've had the codes checked and they're clear. Unfortunately, my mechanic can't replicate the hunting at his workshop, but I've sent him a couple of videos and he is steering towards gearbox problems, most likely the torque converter.

After a bad run with some other items on the car (passenger door lock actuator, passenger window winder, rear brake caliper failure...at the airport on a sunday night!!) I'm loathe to spend the £1,000-£1,500 to replace a torque converter without being sure and not having any error codes. When I was researching these cars, the S-tronic auto seemed to be pretty bomb-proof too. In a bid to rule out other engine gremlins, I had a terraclean carried out on Friday past and the car is definitely running smoother, shifts are cleaner and at lower revs (increased torque) and mpg has improved slightly. Unfortunately, the hunting is still there though.

I guess my question is, has anyone any similar experiences and, if so, what was the outcome? Also, I've seen a post where an A8 owner, after ruling out the Throttle Body, changed the torque converter at a cost of circa $3,000 and it turned out to be the electronics of the throttle body after all. The mechanicals were fine, but the underlying electronics were faulty. My mechanic is confident that the throttle body is fine....I'd rather try a swap of that before commiting to the big spend on the TC....

Or do I just drive it til an error code eventually comes up....Also, if it's relevant, I reverse park into my driveway, which is a slight decline of about10-15degrees, so fluids will run to th eback when she's parked overnight

Any help, experiences or advice welcomed....getting pretty frustrated with what was, up until this, my favourite car ever.....Thanks in advance

[damtom85]

Are you sure is s-tronic gearbox, in my opinion you should have tip-tronic gearbox

[cmarg]

Could be my mistake. I thought the older boxes were tip-tronic and then the slightly newer ones were either S-Tronic (basically a tipe-tronic by a different name) or Multi-tronic (the plagued CVT type).

In any case, mine is a tip-tronic, i.e. standard Auto with manual selection ability,

thanks

[damtom85]

You have tip-tronic, ZF manufacturer model 6hp. S tronic is dual clutch gearbox produce by AUDI and very unreliable.

You said, the oil was changed not long time ago, what type of oil was used? Manufacturer and type

[cmarg]

Thanks again. The original OEM oil was used, the brand isn't on my invoice (I use an indie), but he orders from Audi OEM only and it was £29 a litre. It was the right stuff, I've no doubt. Also, the hunting was there before and after the change. My mechanic also said that the old oil wasm't that dirty or thick when it came out and that he would expect me to get at least 60k before I needed another change of fluid

[damtom85]

Instead of buying new converter, I would find tiptronic specialist in UK, take car to them, they will dismantle gearbox from car and take it apart, they will assest what's wrong with it. They will give you rough cost. This is much better than buying just converter and praying for this to cure a problem.

[cmarg]

Thanks for that,sound advice. Although unfortunately, I live in Northern Ireland and auto-gearbox specialists are thin on the ground here. I'll have a hunt about and see if there's anyone suitable here.

Anyone know anyone good in N.Ireland? Or has anyone else any experiences with this sort of problem?

[damtom85]

If I remember well there was similiar topic in here, usually oil changed sorted out problem, I think there was case someone changed converter or mechatronics inside gearbox, this solved problem.

[cmarg]

Thanks Damtom. In the absence of a suitable auto specialist, my current options are to live with the problem until an error code presents itself or try torque converter/mechatronics, but splashing on those, with potential for no improvement is what's keeping me on the fence.

A brilliant, if frustrating car to own...german engineering isn't what it used to be....

[Scott K]

There's a very good ZF specialist in Glasgow which is a bit easier for you to get to. Could always call them first.