Towing <span class="highlight">caravan</span> with 2002 Prado TX Turbo diesel

Thanks Bruce and BlueFella,

Based on the details at this link Prado specs should I be aiming at keeping the rpm to 2000 as the Maximum Torque Nm @ RPM for the 1KZ-TE is at 2000 rpm. In the same link they comment "Useful torque between 2000 - 3000 rpm but little elsewhere"

OK then, you should be running the engine between those figures while towing and towards the top end when pulling hard such as up a hill etc.

I would assume that there would be plenty of useful torque beyond 3000 RPM but the best of it would be between 2000 and 3000 from that info you provided.

Remember that the faster the engine is revving the better the turbo is working, within those limits of course. The more an engine labours the more fuel it is using needlessly and the turbo is spinning below its optimum in that situation.

After an hour of driving you will get the feel of the combination when towing and you will quickly learn what works best for that combination of vehicle and trailer. Just don't be frightened to use your gears if needed.

I use my auto like a manual when towing and I find it works best for me.

Cheers, Bruce.

Thanks Athol,

this will sound like a dumb question but I am going to ask it anyway.

With the auto on the Prado being 4 speed is 3rd equivalent to selecting D with overdrive off?

I will get a transmission cooler fitted but looks like a scanguage II is not compatible with my Prado

Paparata R
That is most likely correct, most autos with more than 3 forward gears used an overdrive as their highest gear, and generally those using 6 or more forward gears have more than one overdrive gear..

Regards
Athol W

The most important thing in keeping fluid temperature down in an auto box is not letting the torque converter do too much work. Some people think of a torque converter as just something that slips and allows you to get some drive from your motor when things are working at slow speed. A torque converter is actually a hydraulic gear box.

Its action is similar to a mechanical gear box. When you are travelling slowly you change down a gear or two. This allows your mechanical gears to convert the engine torque to a higher torque albeit at a much lower output speed than the engine speed. In our turbo diesel engines when we are travelling with an engine speed above 3,000 RPM the torque converter will not do much work, the converter output speed is nearly as fast as the input speed and the stator will be free wheeling and also turning at the same speed as the rest of the converter. If you are travelling with the engine speed below 2,000 RPM the stator will be locked by its free wheeling clutch. The transmission fluid wil be travelling in a motion that increases the torque through the converter. The output speed will be slower than the input speed, just like happens in a manual box when you shift down. Better description in these pages.

The problem is that more heat is produced in the torque converter when it is working harder and increasing the torque. If you are climbing a hill and your motor speed is around 2,000 RPM or a little more your converter will be doing a lot of work and thus producing more heat. If you manually select a lower gear and spin your motor up to 3,000 RPM or a ittle more the converter will be doing less work and produce less heat.

If you use this technique and keep your engine speed up on hills there will be no need for an extra heat exchanger.