My mechanic says I need a new transmission oil cooler hose / line.

What is your question?

He says mine is leaking. I can find no fluids of any typoe on the ground, and after checking the transmission fluid everyday for weeks, the transmission fluid level is not going down. Now, the fluid is dirty, but can the transmissiuon fluid leak somewhere that I cannot see it, and why does the fluid level stay full?

How long has your 2013 Chevrolet Tahoe had this problem?

I didn't know I had a problem.