3ltr BT50 Transmission Hot.

Dodger - Ross has nailed all the points well. All automatics should be fitted with an oil cooler for towing, particularly long distance towing, or towing in hilly country.

I understand the current Mazda BT-50 6 speed auto transmission is the Ford 6R80 model transmission, as fitted to the current model Ford Ranger and the F150 in the U.S. - and the Americans manufacture an aftermarket transmission oil pan for the 6R80 that is cast alloy, and which holds another 2.8L.

Both the extra oil capacity and the cast alloy pan help greatly with heat dissipation.

An automatic tranny shouldn't exceed a temperature of more than 250 deg F or 121 deg C, or you will find seals becoming hardened and leaks starting.
On these electronic transmissions, overheating will melt the plastic insulation on the solenoids and wiring, resulting in solenoid failure.

One U.S. transmission repairer recommends a maximum of 200 deg F (93 deg C) for the 6R80 - and claims that every extra 20 deg F (over 200 deg F) in operating temperature, reduces transmission life by a factor of 2.

http://etereman.com/blog/ford-f-series/potential-problems-to-look-out-for-with-the-6r80-transmission/

All OEM designs utilise the minimum amount of oil that the engineers reckon is good enough for average operating conditions, with a small portion of extreme operating conditions included.

Towing a big van a substantial distance on a hot day, is called constant extreme operating conditions - and this is operating conditions way outside Mazda engineers calculations.

Cheers - Ron.

Yes they do get hot and normally run hot, but, when towing, the temp of the fluid leaving the auto torque converter is often in excess of 100Deg C and that will boil water.
In hot weather the bottom of the radiator, normally cool, is quite hot purely from cooling the engine heat. This leaves little left to cool the auto fluid heat also being added to it.

The auto which is working hard will/can/often does overcome the system and overheating results.

If an average person has noticed it is HOT then it would be very reasonable to assume the system is near it's limit. With no reserve left, any additional loads or heat will cause a failure.

Just replacing the fluid regularly , which isn't ever done on BT50's, doesn't guard against or prevent problems with heat loads or hot ambient conditions.

It is very expensive to "suck it and see" when a the modest cost of a cooler can ensure control of fluid heat is handled.

sjp
What is being discussed is a transmission cooler, not an air to air turbo intercooler.

opps ,shows how much of what i read actually gets processed by my brain .

Ron,
it is an older 3litre bt50 and I don't believe they had the 6R80 transmission.

Thanks, Rockape. The OP didn't specify the model and I just presumed it was the current model.

So - Dodgers transmission will be the 5 speed Ford 5R55W that was a product of the Bordeaux Ford transmission plant.
Ford sold this plant to a French steel forging company in 2009 (the HZ Holding France SAS company).

HZ Holdings only continued to produce this transmission until 2011, when Ford ceased using the 5R55 transmissions, and the factory was turned over to making wind turbines.