Our 6-speed auto box in a 2006 Signum 1.9 CDTi has developed a delay, followed by a thunk when we first engage drive. This only happens in the morning (or at the start of a journey), but after that it changes gear fine. No spanner light on the dash and no problem when stopping at lights (where it shifts into neutral) and setting off again (when it re-engages 1st).
Local garage checked the ATF and said is was brown/black. Glycol test for checking contamination with coolant proved negative.
Rather hard sell to change a piston and housing, torque convertor and fit a new cooling unit / coil - all for the princely sum of around 2.5-3k (in VAT).
I suggested trying a ATF flush and see if that cured the problem, which went down like a lead ballon. Stating with 100% confidence that it would be waste of money (£100 ish).
What I still do not know is what caused my ATF to be become black - although they did not mention a burnt smell. If the cooling coil has gone, does any know how long the ATF would be expected to last before it went bad again. Are talking weeks, months etc?
If anyone has gone through a similar situation I would be keen to hear what happened. After my ATF flush the problem may come back and I may have to return to garage with my tail between my legs, but for the sake of 2.5K......
Thanks in advance for your time and effort,