Modern Chrysler gearbox

[Peter.Kent]

My 412 has been fitted with the modern torqueflite as found (e.g.) in the Blenheim. So, three speeds as before, plus lock up, plus overdrive. 2000rpm = 80mph.
But sustained vigourous running results (after 45 mins aprox) in the lock up tripping out and therefore a return to 3 speeds only. The gearbox has two flexible pipes connected to the bottom of the radiator. I assumed that this was an oil cooler. I became increasingly convinced, though, that the problem was excessive heat in the oil. Thus having completed a long journey with three gears, I parked up, came back an hour later and I was back with all the gears. Research on the web suggests that the principal purpose of the matrix within the radiator is to warm the oil in extreme conditions in places like Oregon. So, it seemed worth trying a separate oil cooler mounted in front of everything. I telephoned Brian who told me that he thought that there was something in my theory and wished me luck!
So, I disconnected the existing houses (noting signs of extreme heat) and got some new hoses made up (Pirtek in Oxford) and connected to an off the shelf oil cooler which I mounted behind the grills below the bumper.
Have just been down to Dorset and the whole set up is working like clockwork. It was not especially warm on Sunday but the return journey from Bridport (125m in 2 hours) would have more than tested the theory. In short, job done.
Incidentally, this modern gearbox requires an unusual oil, ATF+4. A Mopar branded product is available (try ebay) but it's not cheap and you need more than 5 litres, so 2 cans at c. £55.
Peter

[Thor]

That's interesting. The principle of using the engine coolant to cool the gearbox is not wrong but it probably needs a much larger heat exchanger to work well enough to avoid excess temperature. Surprising that the existing Bristol item is not enough, however, as the standard gearbox had no torque converter lock-up, and without lock-up the torque converter slip tends to generate quite a lot of heat. Maybe the radiator components are a bit furred up inside.

[Peter.Kent]

The gearbox was fitted with a new rad with the oil pipe inlets etc in place. Guess it's a Mopar item? So, it's not furred up. I suppose the root of the problem may be that this gearbox is actually designed for a truck. P