The internal radiator 'cooler' also heats the transmission fluid to operating temps on cold days.

Does anyone know if the tranny fluid goes thru the radiator or the external cooler first?

You would have to look in a repair manual because it's hard to determine flow direction. If I had to GUESS, I would think that it pass through the external first.

Koz

There would no benefit of the AFT entering the auxiliary cooler first and then getting heated back up again by the radiator. I am almost certain that the AFT enters the internal radiator heat exchanger first, and then additionally gets chilled by the external auxiliary air-cooled heat exchanger, located by the horns. But I cannot confirm this yet. I believe the two heat exchangers are plumbed in series. The ATF leaves the Tranny then enters the radiator then enters the external cooler and then finally goes back into the Tranny.

The two heat exchangers are plumbed in series. The reason I think the fluid passes through the external first is because for one the rad exchanger is the primary exchanger (more effective) and also helps heat the fluid when cold. How effective would this be if after the rad exchanger heats the cold fluid then the auxiliary exchanger cools it back down? Also, when the fluid is up to temp and over heated from stress (towing, etc.). The external exchanger would first shed some heat and then pass through the rad exchanger which would shed what ever excess was still in the fluid and also still maintain operating temp.

With all this said, you may be right!

Koz

Someone (but certainly not me) should disconnect a hose & see which direction it is going!

I will do it.

Yeah looks like I was wrong. I looked again at the oil cooler in front of the radiator, and the hoses also states A/T oil on it. It seems to indicate a flow from the bottom of the radiator connection through the cooler and then back to the tranny.

This is why I love this forum! Let us know!

In all cases I have seen, any additional trans coolers are installed after the fluid leaves the radiator cooler. There are several reasons for this. Once the engine is up to temp, the temp of the radiator coolant remains pretty constant, but the trans temp can vary greatly, depending on the load. All heat in the trans is generated in the torque converter, and the harder it works the more heat it generates. This is why the trans cooling circuit usually takes fluid exiting the converter and sends it to the cooling circuit before returning it to the trans. As for the radiator cooler heating up the fluid when cold, I think this is marginal, at best. If you start off with both the engine and trans cold, the trans fluid will probably be up to operating temp before the engine because of the immediate 'work' the torque converter is doing. I don't know the specific amount of thermal exchange capable in the radiator cooler, but it would seem that it is a fixed amount. So, as I said, if the engine coolant temp remains fairly constant, then the temp of the fluid exiting the radiator cooler would depend on how hot it was when it entered. The harder you are working the trans, the hotter the fluid will get. And if the fluid temp can't be lowered enough by the radiator cooler alone, you need the extra cooling capacity of the add-on system. Over cooling the fluid is a much better situation than under cooling it. The trans is better able to handle lower fluid temps than too high. And once the fluid is damaged by overheating, it can't be fixed, only replaced.

It takes 20-30 minutes for the tranny temp on a Titan with towing pacakge to get in the normal range on the tranny temp gauge.

I will be under my truck very soon to install an Amsoil by-pass system. While I'm under there I will look for some indication of the trans fluid flow direction, maybe an arrow somewhere.

Koz

If you want to trace the lines, the line closest to the front of the transmission is the pressure side to the radiator. The return line is the one closer to the rear of the transmission.

The Titan has a tranny temp gauge!? Do they have the same 5 speed? If so, where is the sending unit port?

The reason the transmission fuild is
routed through the radiator is to heat
the fluid on cold days to make shifting
smoother and if it gets over 190 deg. the
fluid will be cooled also.

The extra radiator is for cooling only.

Cliff s