Good afternoon, I have a 1996 Ford.

Good afternoon,
I have a 1996 Ford Explorer 4.0 2wd with about 110,000 miles. It runs great and I've never had any problems with it, other than having the A/C redone. I had a complete transmission service done about 10,000 miles ago and it's never leaked and works perfectly. About a week ago, I left my house in the morning, and about 2 blocks later, I was pulling away from a stop sign and it had a slight slip. I went back home and checked under the car for leaks, and checked the fluid. It was low, so I added about 12 oz. And it worked fine after that. A couple of days later, the same thing happened. Again, it was low on fuid, but no visible leak anywhere. I decided to check my coolant, and found transmission fluid in my radiator.? There is no coolant in the transmission fluid, but there is transmission fluid in the radiator.? The radiator has had a small leak for quite some time, but never really got much worse. I've owned a lot of cars over the years, but never heard of this before. Could this have anything to do with a bad radiator?
Thank you