Should auto discovery get this hot???

[scubawall]

I have a 1996 discovery es 300tdi, currently living in spain 12 miles from coast but 910 metres above sea level, the transmission hot light comes on approximately half way up the hill (500 metres in altitude)when towing a 1 tonne trailer. The temperature is usually about 30 degrees C. Is this normal, I have changed transmission oil but not much change. Do I need a larger oil cooler or is it likely a transmission overhaul? The red light doesn't go out until i get home and let it rest, the last mile having 200 metre height gain and no tarmac.
Any help much appreciated.

[JulesV8]

Hi There,

Just looked at the manual and they say use ATF Dexron IID and this covers it from -30 to +50.

It may be that its working hard or as you say, the oil cooler may need replacing. What are the fins on the cooler like? Before going to that massive expense, what kind of fans do you have? Vicous standard or aftermarket electric? It might be worth going to a scrap yard and picking up an old electric fan and fit it in front of the gear box oil cooler to help reduce the temp...maight work out cheaper.

the other thought, when you replaced the oil, when filling, did you put enough it (Engine on, go from N to P to R, check level?)

And make sure you dont over fill it!

Good luck