While driving at highway speeds the “n” light on the gear shift starts flashing. This indicates that the automatic transmission is overheating, and that I should pull over to let it cool per the owners manual and a sticker on the drivers door. Which I do - I let it sit for about 5 mins and its ready to go again. However, this is inconvenient and has happened on numerous occasions. I have search all over the internet for a solution, and the only thing that seems to be the solution is to get a bigger pan? It seems costly to do this. Does anyone have any other solutions?
Your transmission should not be overheating at highway speeds, and if you continue to ignore this condition, you will soon be paying a few thousand $$ for a trans overhaul. I strongly suggest that you take it a.s.a.p. to an independent trans shop for evaluation. Do NOT go to AAMCO, Lee Myles, Cottman, Mr. Transmission, or any other chain unless you want to be told that you need a new transmission–whether you really do or not.
It is possible that your radiator (which encompasses the trans cooler) is clogged, and that the radiator needs to be flushed or replaced. The coolant should have been changed at least 3 times so far, so if that has not been done, it is possible that a clogged radiator is the source of the problem.
Incidentally, this trans should have had its fluid and filter changed at least 3 times already, so if that has not been done, you should have the trans shop take care of this service while it is there, as long as they don’t tell you that you do already need a trans rebuild.
If this turns out to be a “normal” situation for a properly-serviced Montero trans, then you should have a heavy-duty trans cooler installed.