Audi A6 C6 3.0tdi tiptronic

[MartinNikolov2311]

Hello guys,i'm writing here cause i really don't know what to do..
I started getting tired of my car..So,i had had the car for around 2 years now,everything was working perfect in December 2018 i replaced the gearbox oil and filter and the gearbox was shifting perfectly before and after that..Everything was in order until i had to replace the timing chains..In September 2019 i replaced them in a shop in my town(which is little and i live in Bulgaria,so mechanics here are not very experienced on these cars..So,they replaced the timing chains with the transmission and engine out of the car..Then they assembled everything and the car was ready..So i drove it and everything seemed fine until the beginning of November 2019 when i started experiencing issues with the gearbox..There were vibrations when accelerating,rough shifting and when coasting the car was shaking forward and backwards.When they opened the transmission oil pan,there was oil mixed with coolant which we supposed damaged the gearbox(i suspect they failed something when assembling the engine and the gearbox after replacing the timing chains)..So in January 2020 i transported the car to the Capital of Sofia where a "better" mechanic was working on my car..So he recycled the gearbox(don't really remember what he told me he had replaced) and sent the torque converter to be recycled too in a licensed garage..So,we replaced the torque converter(with a recycled one) and everything was smooth for a month and 2000km(except one thing that i noticed that when the torque converter was locking up in 3rd gear around 32-33km/h it wasn't really smooth but was rapid and it was feeling like something pushed the car from the back for a second) on the other gears everything was perfect,then same started again..When i'm on "kickdown" right before shifting up at 4200-4300 rpm the engine revs to 4600 rpm for around 0.5-0.7sec and then engages the next gear(something like changing a gear in a manual transmission without letting the accelerator off)..When i drive on manual mode and i stay higher than 1600-1700 rpm it is almost gone,but if i try to accelerate harder from 1300-1400 rpm there are hard vibrations all over the car..Also when i'm coasting and let of the gas when the engine goes under 1600-1700 rpm the whole car starts shaking front and back(like in a manual transmission i press the clutch and then let it off and again and again) and the rpm gauge also shakes.. P.S. when i cold start the car and all of the fluids are cold until the coolant gauge reaches 70-80 degrees the gearbox works almost normally(i mean there are no vibrations at all and it shifts smootly) but there is severe clutch slip and the car accelerates slower i suppose is from the fact that the torque converter doesn't lock up until the transmission oil reaches optimal temperature..When the coolant reaches 70-80 degrees the torque converter starts locking and the vibrations show up but then the car accelerates better..
I would be really thankful if someone could help me with some information about my problem..
P.S. Also the first time(before recycling the gearbox) i had loss of coolant,but now i do not and i still haven't opened the gearbox oil pan to see if the oil is mixed with coolant again.

[niedzial1983]

what was the reason for the gearbox oil change on the first place? tiptronic is sealed for life and if the oil change was done incorrectly this will be cause of the issues. when chaning oil you need to ensure the tranny is flashed and after 1k miles the oil needs to be changed again to enusre all metal fillings are flushed