Another interesting gearbox fault.

[ian_s]

Evening all,

I have a gearbox issue I hope someone may be able to shed some light on, i'll try to describe it accurately. I'll also say that I'm a mechanic by trade but I have zero A8 or ZF trans experience.

Basically my daily journey is half B road and half on the M1. When the car is warmed up I slow down for the villages and the gearbox thumps/jolts down the gears, not every shift mainly the higher gears around 40mph. On the M1 it is absolutely fine with no jolt when I use kick down to shift. When I pull onto the slip road the inevitable jolt comes.
If I drive in S instead of D I have no issue at all, its like the higher revs sort it out.
Sometimes when stationary it also jolts as I move the selector into D or R.

In the couple of months I've owned the car I've changed the trans oil along with a new filter in the sump. I didn't find any nasty chunks on the magnets or burning in the oil.
I also changed the air mass meter as these can cause all sorts of auto trans issues.
The F125 selector position switch also needed changing to sort a 01119 fault in the abs fault memory. (pig of a job!!!)
All parts used were genuine.

The only re-occuring fault I have in the memories is the engine saying that both cats are defective, this has only came about since the air mass meter replacement.

Anyone have any suggestions? It's like it doesn't know when to shift so the jolt is the torque convertor trying to catch up?

Any help is greatly appreciated,

Thanks in advance.