Tiptronic snatching in auto

[lpg boy]

I bought a 2003 v6 4motion Highline estate a couple of years ago with the 5speed tiptronic box . Done 15k in this time.
I was told the gearbox oil was changed at 80k when I bought it. It is now at 125k miles. A new genuine gear selector position switch was fitted at 114k.

Problem started about 3 months 2k miles ago.
Initially the revs would fluctuate at a steady 45mph without speed change. Now the problem is when in D gear change is no longer smooth and seamless, but jolts and gives a bit of a clunk taking up the drive.

I have checked the engine and gearbox with VCDS and there are no faults. (lots of vcds experience as previously owned a different B5.5 for 12years)
There are no leaks so presuming oil level is o.k. Also I found that Tiptronics should have a different, more expensive oil.
Any idea what happens if the oil for ordinary autos was put in a Tiptronic for economy, or is low.
Is it on it's way to becoming terminal or something stupidly simple ?

thanks

[rowdy-999]

I would change the oil and filter to start with, using only ZF or OE oil.

[lpg boy]

Have found out oil was changed in 2011 . Oil and filter change as you suggest is where to start. Will start saving for oe oil and filter through TPS .
Thanks for pointer.

[Gazwould]

What is the oil spec code ?

[lpg boy]

This has been a long job to sort out, but has been down to 3 stupidly simple things.

The clunking on gear change was suggested to be knackered spark plugs but they were only 4500 miles old so I was very sceptical. I know LPG knackers spark plugs but 4.5k was unreasonable so took one out to have a look. They were single electrode NGK Iridium IX BKR6EIX-11 so were not cheapies. Found the earth electrode had dished in line with the centre electrode which struck me as odd because they were not like this when I fitted them.
Rang NGK tech help and had a good chat with someone with an interest in his job, not a crib sheet reader. Straight away he said they were the right heat, but wrong plugs , the -11 means 1.1mm gap so even on petrol the gap is too big even before wear takes place - so much for professional sellers advice. The electrode dishing became more of a physics lesson in that the spark does not 'jump' the gap, but being electricity it takes the easiest route which is from most conductive molecule to molecule until it gets to earth. Petrol is full of additives and the spark has an easy life hopping from one to the other. Unfortunately LPG is more of a pure fuel and the extra useful conductive molecules are just not present so the electrons (spark) are hitting the electrode with more impact due to the molecules being further apart to jump there from. My eyes hadn't quite glazed over at this point so my practical LPG learnings from the last 20 years were starting to make sense. From this he recommended an immediate short term fix was to reduce the gap to 30 thou plus the eroded bit which was not measurable but what I really needed was the designated NGK Laser line LPG 1 plug. When I got these I found the gap was 35 thou and the earth electrode had a patch of something fused on to counteract the erosion, don't quote me but he mentioned platinum but information overload was setting in.
Fitted and working, this stopped the clunk when leaving a slow corner after entering on a long over-run when the auto threw it down one gear then grabbed another to have a stab at the right one.

Gear change still seemed a little early with the hunting problem still there.
Following the advice on the forum for genuine parts for the auto service , mortgage in hand went to TPS for oil, filter and gasket. Provided I didn't open the them they would credit any unopened ATF bottles, so got 7
Talking to someone that works on specialist and custom cars about doing it myself, he said from Autodata the Tiptronic level needed to be checked a)at temperature, and b)the final check is made with the engine running ensuring the torque converter was full. Change of tack, I'm not laying under a running car, up on blocks and doing that last fill to level.
Off to Auto Shack and watched them do the job close up.
Drained oil, removed pan and filter - made in china 2013 so was probably a cheap oil and filter change when it was done, cleaned it all up and re-assembled with new genuine VW parts. When the oil had been refilled correctly over 5 litres went in, but we only drained about 4litres, so they think the previous engine running level check wasn't done it - took us about another .75 litres for the final level after the engine was started.
Gear changing was now smooth but I still felt it was changing up too early because after a change with soft throttle it gave a momentary over-geared feeling and the revs then blipped a bit.

Thinking back to the conversation with NGK guy he claimed when the lean burn engines came in the spark voltage was increased to push the spark harder across the fewer molecules in lean burn combustion and some manufacturers did quiet uprates of the coil packs to help the power and economy.
My engine has a coil & h.t. lead system that was original, so I looked up the expected life of h.t. leads and the manufacturer said 80k, so they would probably go 100k before problems mine has done 130k+ now so probably tired enough to affect running efficiency especially on LPG
Fitted new copper core leads, hoping they will last the car. This has removed the feeling the auto has changed up too early giving a smooth increase in speed under both hard and soft acceleration with the only indication of low rev gear changes is the rev counter needle drop because the engine is so quiet.

Job done but a B5.5 will always keep us guessing.

Why LPG - 2.8 30v V6 estate driving through the full time Quattro system costs 13p/mile to run and tows (at 15p/mile) like a tractor but much faster, beats boy racers from the lights up to 60 mph with trailer on, you should see their faces when they catch up. And of course, most of all, LPG is better for the environment than some other fuels.
Talking of tractors, my wife has a 1.9 TDI 100hp B5.5 estate and now diesel has gone up it costs her 13p/mile to run and towing a trailer hits her's really hard.