In stock form, my first A340 lasted about 8 months, daily driven, romping on it on occaision, and lots of healthy highway pulls.
Second transmission, (Still a stock one), simply with a tube/fin tranny cooler, Installed and mounted right where my driver side Foglight should be.
I've made A LOT more power to the wheels than I originally did with the old tranny, plus, it's been over **2** years, and still holding STRONG.
If your tranny has already went down the way of south, then so be it, but if it's still decent, save it and make it last longer! Coolers, (Like Dave said), Generally you can find a decent for $50-80.
It's a great investment, they're easy to install as well.
You just need to get creative with where you want to mount it.
-Jeff