Jerking when downshifting 4th to 3rd

[M-A8]

First thing I would do is what guys already said, gearbox service.

With the following things I guess not everyone may agree, but it's not what I think or came up with, it's base on others experience and advised by the Audi's ex Master Technicians who look after my car (they worked for Audi across the globe over many years, from US through Ireland and Europe and few years ago they've opened their own Independent VAG garage and now they are one of the best if not the best independent VAG garage in London)
I know for a fact that some Audi's Master Technicians call them in if they stuck on something. Plus they do a lot of the gearboxes, from service to full rebuild.

Anyway. In their opinion, if there is no obvious damage you don't need to use sucking machine, draining off at the temp of 50degrees is absolutely fine.
As they fill the gearbox with same original oil which was in your gearbox from new so you don't have to worry about some oil left in torque converter. This oil is just fine.

It's not that they can't afford the sucky thing as they are flat out 6 days a week for few years now, but in their opinion it's not necessary.
They could be wrong, plus guys here are way much more experience than I am, but this guy's reputation is just outstanding.

I'm saying that coz it's not easy at all to find a ZF specialist near you, unless you live around Glasgow

Don't forget to change the seal and filter at the same time.

Another great thing I think which one of them ''introduced'' from his experience in US is this.
http://www.ebay.co.uk/itm/Lucas-Oil-...item1c44274c7c

It wont harm even if you have no issues with your gearbox as it's a good maintainer, but can solve quiet few issues which you would thing need some work done to your gearbox.
I know two A8 and one Q7 owners which noticed difference especially with slips.
They were noticing a loud noise when putting a foot down (slipping) and after 500+ miles with this fluid the noise was gone.

This type of service with VAG guys will set you back around 400-450quid.
200 for the original ATF, 40 for the seal, 40 for the filter + labour +vat

I was really really making my trip to Mackies in Glasgow on the way to annual meet, but because they've had no appointments on the day I was traveling I was kind of forced to do it with my guys.
It's not that I didn't want to use my guys, but after so many good reviews I just wanted to experience Mackies service.

I know that Mackies are the best in the business and I would never ever question their professionalism, but this job can be done by a really good and trusted VAG specialist as well.

I'm fairly lucky because my car was well looked after from new and it's even more looked after since I'm the owner, so after draining the oil and comparing it to brand new oil, your seriously couldn't see the difference in colour, you wouldn't recognize which one is which, BUT this does not mean that oil was same quality what brand new one !!!

There was some dirt on the magnets (bottom of the oil pan) but filter was crystal clear.
Even with 150k on the clock now (and still 6.9sec 0-60 ) I've been told on few occasions, mainly by other A8 owners, that my gearbox runs really smooth and gear changes are almost difficult to notice in D (if not the loud exhaust) and very smooth in Sport, so I am very pleased and I'm a hard believer of maintenance maintenance and maintenance, if you you don't look after your heart (engine) and legs (gearbox) , you wont last long.