I'm under impression that my gearbox, when it goes in limp home mode, starts to heat up the cooling system.

I think that, from some reason, when in limp home mode, the ATF gets warmer than usual, causing heating up of cooling system (i't doesn't overheat-> it warms up to 96-98'C, and fan kicks in and lowers it to 92-93'C).

There is a line that goes from the gearbox into the radiator, which does the cooling of the ATF, right? Now, does the upper line lead into the radiator or out of it?

Reason for this question is that I'm going to put a small radiator for cooling the ATF (oil cooler from a vectra GT or something like that), and I want the ATF to go from the box, into that small cooler, and then into the engine cooling radiator, and then back into the box.

So, i must know, which of the two lines leads ATF from the box to rad?

I'm not sure which line is which however woudln't an additional cooler just be masking another problem?

There is no indication that the transmission cooler is inadequate when the gearbox is operating correctly. It could well be that more heat is dumped into the fluid in limp home mode because the gear selection is probably not always optimal for the driving conditions. For example, if the car is in too low a gear, of the torque converter is not locked up by the ECU, the torque converter will be operating less efficiently and the fluid will get hotter.

I think your solution lies in resolving the underlying gearbox problem not by treating the side effects of the problem.

Kevin

good thinking....

it just may be that the torque converter doesn't lock up...that may cause ATF to heat up, right?

I'm just in the process of repairing the box.

Torque converter lockup requires an electrical signal from the ECU and there is no manual override AFAIK, so it almost certainly won't engage in limp mode. That in itself could account for the slight increase in running temperature as the gearbox dumps more heat into the radiator.

Kevin