I like the B&M trans coolers with the fan alot and will use one when I put a cooler on my LJ. I have had several other B&M coolers with no problems at all.
The first time I installed a cooler and temp gauge was after I put a high stall speed convertor in my 80's Monte years ago. I used a B&M gauge with the sender mounted inline on a tee and a huge standard fin cooler.
I installed it in the spring time the gauge did not seem to work,the needle never moved. So I sent it back after checking everthing else and the new one didn't work either. A couple days later we had a warm spell and in rush hour traffic the needle moved a little.... I learned a lesson about minimum trans temps.....
I had to run the fluid thru the radiator even in the summer, it also lowered the water temp as a bonus and gave steady trans temps at the drag strip all day. I ran a tee sender in both lines and ended up going thru the radiator last for proper temps year around. I wont use a tee sender on the Jeep but never had any trouble with the fittings in the past though....
