hi, I buy a oil temp gauge to my E40D , but i like to know the better place to put the sender, oil pan? in the case ? where?...

put in in the tranny cooler output line ( the front one / closest to the engine ) - it is more accurate there - in the pan when its to hot - its too late -( its were ford puts them on the newer trannys too )

The trans cooler line going to the cooler (where F250rollinon37s said) is the area where the fluid is the hottest. But there is no provision for a gage there, you will have to do some fab work.The trans pan is where most reputable builders will say to put the temp sender for the most consistent readings, also requiring some fabrication. If you decide to install it in the pan I would use a 4R100 4x4 pan, it bolts right up to a E4OD, it is deeper than a 2wd pan and it has a drain plug that the E4OD does not. For the easiest install the test port on the drivers side just above the pan rail, there is a 1/8" NPT plug. You can just screw it in there. Depending on how long your sender is be careful that you don't bottom it out. Any location is better than no gage at all.

putting it in the pan does no good. It tells you the temp of the fluid entering the clutch packs, torque converter, etc. You want to know where the hottest fluid is, as that temp will tell you when the trans fluid starts to degrade, tells you when the clutch packs or bands start to fail, and tells you how hard the torque converter is reading. The only place to get that reading is in the cooler line.

Summit and other places sell trans temp "blocks" that basically let you put a cooler line into it on one side, cooler line out on the other side, and a sending unit on top...

Thanks mates :)