Transmission Fluid in radiator several weeks after transmission repair. Any idea why?

I think you need a new radiator.

Thank you. I thought that might be the case. Do you know why they would bypass the oil coolant system?

For the engine oil cooler in the radiator, people by bass those because of test done in the city driving in the summer, standing stopping traffic actually heats up the engine oil to a undesirable temperature, braking down the engine oil faster. They found just the oil pan itself cools the engine oil good enough.

Thank you for the answer. I guess I will have to see what the mechanic finds in the morning. I am hoping to keep this on the road, as I really do not like how complicated and computer laden these newer cars have become.

That sounds about right since I have had truck two years and no problem with cooling or engine at all, at least not since this transmission rebuild. Since I do not need truck every day for work and usually take out a few times a week for local errands this is the first real long drive since the rebuild. Thank you for the advice.

Make sure that no coolant has got to the transmission. If it has the transmission needs to be flushed immediately.

It turns out the radiator was disconnected from transmission and the transmission cooler installed so two cooling systems are now separate. The transmission fluid in the overflow was what was flushed out of the system, and everything should be fine according to the mechanic. The smoke was apparently steam from too much fluid spilling onto engine when it heated up. So hopefully all will be fine and I will take some longer trips over next few weeks to be sure all is OK. Thank you Bob and also for all the other replies. I can fix things around the house but not well versed in automotive repairs so I appreciate the advice.