A750F 5spd auto limitations

[HK1837]

All

Just a heads up. I think I have found the limitation of these boxes. The A750F was fitted to all 2005-2015 V6 auto Hilux, all 100 series 'cruiser and I think most 120 and 150 'cruiser as well plus FJ Cruiser. The last couple of years of 3.0L D4D auto Hilux got them too.

The known weakness in these is cooling, you can't tow or drive on sand with one of these without an aux cooler fitted without doing damage, but this is no different to any auto box. Even with a factory cooler like a 100 series has, driving in high range on sand or towing big loads like 2500kg in drive will still overheat the fluid. For example my next door neighbour's 100 series diesel was traded at 160,000km and he later found out the fluid was as black as liquorice. They also have a weaker clutch pack for 4-5, which is a common fail point.

The weakness that is far harder to address appears to be in the torque converter itself. I've always had an aux cooler and an analogue gauge on mine (sender where fluid exits the box to the cooler), and have only ever towed 2250kg. Sure the engine has far more power and torque than any other 2005-2015 short of another supercharged V6, but the thrust plate in the torque converter has started to fail - we found brass/bronze shavings in the pan. The transmission fluid was changed out with a full flush 18,000kM ago, and has been running Valvoline Maxlife since then. With converters in big power SBC, Ford, Hemi etc they replace the plate with a needle roller setup, but both Wholesale Autos and Dominator tell me that you cannot do this on an A750F converter. I'm going to try some US places to see what they can do with the converter.

So yesterday I bought a good lower kM 2009 TRD box and transfer, off a wreck that had never towed. We are going to put that into the car, and run the new 140deg boil point full synthetic fluid, and then have a look at my box and see exactly what is failing. Hopefully we can find a fix! If we rebuild mine we will machine it and add extra clutches in the 4-5 area too.

Note this new fluid has been bought into the country specifically for Ranger/BT50 and 200 series boxes that people are cooking. They whack on a 3000kg van and then stick them in drive and promptly cook the fluid. Standard Ford and Toyota fluids are apparently starting to boil by 110deg or thereabouts, with a flash point of about 175degC for Toyota WS. Even Maxlife apparently starts boiling about 115-120degC with a flash point of about 200degC. This fluid (can't recall its name but will get it) has a higher flash point again, like 220-230degC. It comes form the USA. Penrite do something similar as well I think.

[hiluxxury]

I've always wondered about this. Towing is a killer and those 3.5t tow rating are insane for so many reasons.

The ZF unit in my BMW (same ZF as found in the XR6 and other RWD cars) will send a message back to the engine ecu to lower torque in certain conditions. It doesn't like temps above 100C... I dont know how the friction plates in the ranger boxes etc are dealing with those high temps.

[HK1837]

A mate changed his Ranger’s fluid at 50,000km. It was blacker than night. Mine doesn’t get hot, I make sure that if the analogue gauge even approaches 90deg C that I change what I’m doing. Auto trans shop told me that doing what I do a Ranger box would have died a long time ago!
I talked to a few converter shops too and the guys at Slingshot whilst echoing what others have told me (can’t modify the converter much) that the brass may be a bush in the front of the box rather than the thrust plate in the converter, and that some auto trans rebuilders swap these out for Babbit or bronze bushes. Will see once it comes out.

I also read the trans temp alarm is 150deg C, which is useless! This is not fluid temp where it exits the converter which is usually 20-25deg hotter than where the Toyota sensors measure.

[HK1837]

Here is the fluid we used:

https://www.lubegard.com/products/atf/#downloads