PPD remapper unit /Transmission cooler

Uppy
Perhaps explain what a PPD remapper unit is, and what it is supposed to do. I can imagine it is to modify change and ratio hold patterns.
Is it PRESET or do you REMAP it as you go? according to your requirements, which most people won't know.
Re trans coolers. There are a variety of them available and it should be selected so as not to inhibit flow rate, is, decent/correct internal size of tube and or fittings. The shape of them varies a lot. Long and thinner and shorter and wider. A decent appraisal of the position available for it's fitment would largely decide on what you can fit. You can add a switched fan to it, Either manual switch or automated via a temp sensor.
Do you have some way of knowing auto trans fluid temp? It is the coolness of the fluid returning to the auto which keeps it ALIVE.
My idea is to fit it into the HOTTEST line, ie, the one leaving the torque converter so the MAXIMUM heat value/amount of dissipated by the cooler and therefore that heat isn't added to the engine radiator water to expect it to cool/dissipate additional large amounts of heat, Protects the engine.

Hi Uppy
I have a 2013 Prado 3l diesel 5 speed auto. While a different model to yours, I am hoping you might find something useful in my experience.
I have no idea what a PPD remapper is, however I am playing with the idea of getting a dyno tune and ECU remap. About $1600. For me it is that or nothing. The reason I am considering this is because I just spent $20k on a new motor after popping a piston while towing. I am doing what ever I can now to avoid a repeat.
The above is just my thoughts and intention with no hard facts to support it.
The following though, is my experience which is sort of indisputable.
I have a transmission cooler from Wholesale Automatic Transmissions. It appears well made and came with vehicle specific mounting brackets etc. Been there for several years now with no cracks or leaks.
Having said that I have found it does not cure any problems. It probably reduces the temperature a few deg. which may well equate to a corresponding rise in engine temp.
After doing a fair few things and not necessarily in the right order, I would approach it all differently next time and do it in the following order.
1. I would fit a OBD scanner first. I have an Ultra Scan which now monitors the engine temp, transmission pan temp as well as the torque converter temp with warning alarms set for all. This reveals interesting and vital data. While the T/C is locked there is no over heating problems at all in the transmission. While towing up hills with the T/C slipping the T/C temp will increase rapidly and can easily hit 150c. Now for me that is scary stuff and rightly so as you end up with very dark burnt smelling trans fluid. Not good I say. That heat is then transferred to the fluid and the pan temp will rise accordingly if not corrected with an adjustment to driving technique.
2. I now have a MM4x4 lockup-mate T/C lockup kit. This works extremely well and I never turn it off towing or not. I have been using it for a few years now. While the T/C is locked there is no over heating problems at all. However this has on a couple occasions remained locked with the transmission holding too high a gear resulting in motor overload and rising engine temp. Just something else to monitor and be aware of.
3. I am currently fitting an EGT gauge. I will then have early warning of any overload situation on the motor which I can correct long before engine temperature rises and pistons start popping. This last point is as yet untested but makes sense to me. As I said I am probably a bit over cautious now having just cracked two pistons and blown a decent hole in one of them. Believe me when I say this experience can really wreck an otherwise perfectly good day.
The bottom line is that these four cylinder common rail diesels while working extremely well while not towing, they are pushing their limits when loaded up and towing. One may or mayn't experience what I did, however starting with an OBD gauge and monitoring some vitals will tell you quickly if you have problems that need addressing. If you can do what you require without any over heating then consider yourself very fortunate and happy motoring to you. No further action needed, however, if not then do whatever is required to address your problem from there.
Hope that helps somewhat.
Roy G.

Personally I would never chip a motor. Both of my cars have an ECU Remap and am very happy with resulting power/torque and fuel savings. One is only 2 years old and one has been remapped for 5 years. The Prado 1KD motor had a bad name for destroying motors. (google it , if in doubt). A good ecu remap will help with engine running with more power and torque. It can also improve fuel economy depending on driving style and tune. Definitely go with the transmission lock up kit from MM 4X4 AS THEY ARE BRILLIANT, ESPECIALLY FOR TOWING. I run Ultragauges and these are great for keeping an eye on engine and transmission temps. Easy to set up and customize to suit your needs.