Transmission cooling design question

Still trying to figure this out. For those of you who have an OBD tool and app to read actual trans temps…

Have you ever been under load (towing or pulling a long hill) and, while still under load, actually seen the tranny temps cool down? As in, have you ever actually experienced the cooling fan kicking on and having any cooling effect at all? I haven’t, and I’m trying to deduce if that might be contributing to my problem. All I know is, while under even a mild load and the trans starts getting hot, the temps are a one way direction up until load is totally relieved. It will not cool down until I stop and/or go downhill and take the load off. Sometimes that’s not convenient or even safe.

Seems odd to me. Isn’t that what a fan is supposed to do? I’ve had other vehicles before where the fan kicking on had noticeable effect on trans temps, enough to overcome the mild load and cool thingsdown without having to pull over. That never happens with my Tundra. Is it designed differently? Is the fan somehowdesigned to only cool the water and not thetrans? Or does it just do a poor job ofcooling the trans?

 

I'm not for sure, but I don't think 3rd gets have transmission cooling plumbing.

 

I know that. There is no auxiliary cooler. But Isn’t the fan supposed to kick on and cool down the tranny too by blowing more air thru the radiator?

 

It’s called a radiator fan, not a transmission fan.

 

Even under no load, I see close to 220 and I don't hear the fan kick in. I'd assume the fan is not helping after a certain speed? I was doing 70+ last week when I saw those temps.

 

Right. But when the trans uses the radiator as a heat exchanger, shouldn’t cooling the radiator also cool the transmission? Thats what I’m trying to figure out.

 

I'm pretty sure the only thing the radiator is used for is to heat your Trans oil. It's not a cooler, it's to help it get up to temp faster.

 

Definitely regulates temp

 

Yeah not sure you could hear the fan kick on or not at 70+ mph

 

Right. Hence my questions. So has anyone actually ever seen the temps come down, while still under load, due to the fan?

Because even at slow speed when I can hear the fan kick on, I’ve never seen it reduce trans temps.

 

Between the generations there is a ton of info on the trans temps. Toyota eliminated the dedicated trans coolers in 2019 I think? A step back IMO. The trans will last the warranty because you can be sure Toyota torture tested it. Knowing that I was not comfortable with the temps I was seeing (220's). Depending on how you use your truck, at the least, it's probably wise to drain and fill every 60,000 miles. I tow a lot and off road frequently so I added an auxilliary aftermarket trans cooler from Genuine Cooling Systems.

This thread is not about your Gen but there is a lot of info in here...

https://www.tundras.com/threads/5-7l-transmission-cooler-kits.60550/

Google search is better than searching in thread. There are several from your Gen that have added coolers.

 

Yes, I’m well aware, but I’m not modifying anything while still under warranty. And most of all I’m just trying to understand how this thing is designed to work.

 

It works like every other car on the road that doesn't have a separated from the radiator auxilliary trans cooler. I'm not sure about the 3rd gens but as far as the warranty goes, I was willing to take the chance for 20+ degree cooler transmission temps. An the kit for my gen uses all factory equipment except for the cooler itself. YMMV.

 

Your 3rd gen acts like my 2nd ('15 Seq) - 75mph = 220 StopGo (repeated 5 or more times a few blocks each) = 248 (for a few seconds then back down to 230s) allowed to idle for 10 mins after the 248 runs = 183. So it is capable of cooling but only if allowed to idle and I think that is because the puck used to warm the trans up faster using some on the way to the heater core hot water doesn't have the Capacity to cool much when its using 195 degree water a few ounces at a time. Its enough capacity to increase temps from 0 and up but not near enough for reducing.

Does lowering the gear its in to one that is a straight gear no overdrive to allow slipping and therefore extra heat - makes the engine work harder but it can cool itself just fine in case condition so move the strain to it for now. Luck.

 

Not in my year of ownership - towing or not. That's pre external cooler install. All transmission Temps monitored with SGII. There is no stand-alone cooler on the gen3. The hockey puck cooler/warmer is truly warmer. If you want to cool you will need to add an external cooler.