second tranny cooler on PB auto

[beagle]

I've had concerns about towing a full height off road van with a gross weight close to 2.5T. I've left in D and it was in and out of lock every 30seconds, with the motor carrying on like a sewing machine. I've left it manual in 4 with better results but have had it go into some sort of limp mode especially up hills. No warning lights, just drops back to idle. After around a minute we 're on our way again. I've now had a second tranny cooler installed and will see if this sorts it out a bit. The OE cooler is quiet substantial and doubling it should save the tranny from getting over hot I hope. Pulling a very high van with a head wind feels like adding another tonne to the towing load and we'll see if it turns to shit again next trip. All other times it goes very well. The exercise was a bit of a challenge (no pun intended) and the installer had to modify the OE mounts, and suggested a smaller cooler would fit in a lot better. I'll post up how it goes and if it works, it may be a cheap mod compared to dumping it and upgrading to a bigger vehicle. Picked up a used cooler from a late model wreck and around $400 to modify and install.

[Cowboy Dave]

Your other option might be to fit a thermo fan to one of the coolers?

Having said that your description of the safe mode is different to my experience of what happens when the transmission overheats. Mine has done it quite a few times and it whacks itself into either 2nd or 3rd and won't change up or down from there until it gets back into safe operating parameters. But within whichever gear it sits into you can still accelerate or decelerate and vary the revs.

When you are describing it going back into idle, that is sounding more like an engine fault. But then it would be unusual to have that without some warning lights.

Have you got a scangauge or something similar? It would be well worth getting something along those lines so that you can see if there is a fault code logged at the time of the limp mode. Also worth seeing if you can get a proper reading on your transmission temps. I gather that the newer scangauges can produce a decent reading for that but I went old school and got a proper gauge stuck on mine. Then you can drive to the temps and manually change down for yourself if you see the heat climbing and avoid the transmission going into safe mode at all.

[beagle]

This isn't locking into second gear like most do. It just runs out of power but doesn't stop running. I just sit on the side of the road with it idling, hit the pedal and nothing. Once it actually revs with the pedal I'm off again, so it's some sensor that's heat affected and I'm punting on it being associated with the tranny getting hot...but I may be wrong.

[Cowboy Dave]

Yeah but unless the tranny has 2 different types of safe modes - or the challenger has a different box (which actually rings a distant bell so might be more likely) - what you're describing is different to the safe mode that the 2.5 triton goes into for transmission overheat.

[beagle]

As a follow up on the auto gearbox using two coolers, it definitely does something to it. It's not dropping out of torque lock as often and doesn't sound like a sewing machine, to the extent that the child bride even commented on it. Won't be towing the high rise for a couple of months now, but will try a bit of the hinterland mountain roads in the mean time to see how it pulls in each gear.

[motoz]

As a follow up on the auto gearbox using two coolers, it definitely does something to it. It's not dropping out of torque lock as often and doesn't sound like a sewing machine, to the extent that the child bride even commented on it. Won't be towing the high rise for a couple of months now, but will try a bit of the hinterland mountain roads in the mean time to see how it pulls in each gear.

Just out of interest do you have a trans temp gauge? If so what temps was it getting to before it went into safe mode?

[hvac guy]

does anyone know the correct operation temp i thinking of making something up but need to know the design operation fluid temp range.

[beagle]

I haven't got a temp gauge fitted, so don't know the temps. I have a feeling by the constant shifting in and out of lock under load, that the tranny was running close to very hot. I have a chip fitted as well, set on mid range.I still have to fit the EGT gauge which links to the chip and drops it back when getting too hot. I might add that with normal driving it goes very well with no issues, only when towing does it turn to shit, either with or without the chip installed.