727 with fmvb question

Ok so the first time this happened I did get 3rd gear back after the car was cool. I drove 125 miles that day just to see if the problem would come back. I had no problems, but I never got caught in traffic.

My plan of attack for this weekend is to get the fluid level correct (it was above the full line....and yes I checked it in neutral) and to run my trans cooler in series with my radiator. Does that sound reasonable?

Last month I put in a new trans filter, new fluid and a 3000 stall converter. I did not see any debris in the pan and the fluid was clean. The filter was also in good shape, but I put a new one in anyway.

If I was getting frothing happening wouldn't the problem show up sooner and also affect my 1-2 shift?

Oh one more thing I should mention. Before I lost 3rd gear I did start to get soft shifts to third. They were delayed if you will. I would stay on the gas, shift into 3rd and a second to a couple seconds later the trans finally decided to shift into 3rd. A couple times also I let off the gas after I shifted to 3rd and then it finally shifted. Weird.

thanks guys for the replies. I really want to get to the bottom of this issue.