The best bet would be to monitor the flow through the coolers. You could do this by removing the rear cooler line at the transmission. Then make sure fluid flows out the line while engine running, in park or nuetral. 1 quart in 20 seconds is general rule. Other than that. I would say the converter hub seal has lost its integrity to seal when excessive converter lube pressure is placed on it or it reaches a certain hot temp. If fluid flow is good through coolers then it problably time for the newest design hub seal. Or, do another cooler, then a seal