Volvo: Transmission and control unit, market model, turbo engines

Question

Hello Ray,

you have helped me many times until now. now I have another question because the problem I have confuses me. my car is a 2,0 litre 850 with auto trans. the trans had a major repair last year and the internal parts were renewed. the problem I have is the  transmission Tcu causes the trans to shift rough especially when the car is started cold and I wanted to see how the car will behave by ordering a used TCU from ebay. the difference between the two tcus are one of them is the tcu of 2,0 litre engine(european model) and the one I ordered is the tcu of 2,4 litre engine(U.S market model) because all the non turbo engines in U.S are 2,4 litres.. when I installed the tcu of 2,4 litre engine I realized the shifting is very smooth and the car performs much better. what confuses me here is should I keep on using the 2,4 litre engine tcu or install back my old tcu which is 2,0 litre engine tcu..  what would be your comments?

many thanks

Answer
Mete,
Since I do not have information that tells what the differences in the control units are, it will be a guess. Most times when I swap control units and the car runs fine I go with what works well. So in your case I would leave the one in that gives me the shifts that I like. If you are not getting any unusual fault codes and the performance is good continue to use it and watch for any flaws.