Hey riverol, is was going through the faq's checking things out about our trannys and your problem and came across this. Is this your post?

960 AW30-40 Self-Destructs in Hot, Hilly Climates. [Cautions from Rafael Riverol] Leaving your 960 stock with OEM radiator, no cooler, and cheap transmission oil, together with dealer maintenance according to the schedule, has resulted in a new transmission in every single one 960 I know about in Puerto Rico at around 50k miles. Not only are we talking about thousands of dollars, but a much worse never ending tale of woes and headaches. Volvo technicians tell horror tales throughout U.S. To help prevent this, install a transmission cooler. The factory kit is a simple bolt on, but not cheap. I bought one for my 960 (1995) for $385. Of course, you should also use synthetic transmission fluid. Mobil is a good choice and readily available. If you are careful, you may want to install a Magnefine transmission oil filter ($20, from their website) and perhaps a transmission fluid temperature gauge. If you want to mount the gauge on the pillar you can get a pod from the MVP website for about $30. If you have a 960, I emphatically recommend you do all the above and watch your radiator and coolant like a hawk for any signs of contamination transmission oil particularly in you have the Volvo plastic radiator. But if you do the above, you should be OK as the transmission on the 960 is a Warner (Asia) unit closely related to the one in the Lexus. Be safe or you will be sorry.
Poolman