Understanding the modern auto transmission

[SDHNTR]

I thought the Tundra (could be wrong here) has a liquid to liquid trans cooler, no? So it's going to sit just above coolant temp or so.

Looking at the temps OP stated for the Chevy, it must be an air cooler.

You are correct. My Toyota has a coolant heat exchanger. Tundras 2021 and newer no longer have an external air cooler. Bean counter influence, apparently. Cost cutting aside, that seems like a poor design choice to me, but I’m not an engineer. I’d love to hear it from Toyota what really happened.

So what you are saying is from an engineering perspective, air cooled tranny coolers run cooler overall? I know a lot of guys are installing auxiliary air coolers after the heat exchanger in these newer Tundras. Yes, I could do that and have in previous vehicles (99, F250 7.3 diesel) I just have a hard time with that as I’d like to think Toyota engineers were smart enough to know what they were doing. Especially when they claim a 12,000 pound towing capacity and I wasn’t even towing half of that. One of my pet peeves is having to improve something in the aftermarket that should’ve been designed properly OEM.

 

[displacedtexan]

Don’t modern transmissions have thermostatic bypass that don’t circulate oil through coolers until it comes up to operating temp? And diesel oil has what to do with transmissions?

Some do. Some use fluid/fluid coolers to bring it up faster and then keep it in the intended range.

Old guys telling you what worked 30 years ago doesn't always work, and can even be destructive to modern stuff.

 

[TaperPin]

Some do. Some use fluid/fluid coolers to bring it up faster and then keep it in the intended range.

Old guys telling you what worked 30 years ago doesn't always work, and can even be destructive to modern stuff.

If my 2025 transmission craps out I trust the old guys who have 30 years experience rebuilding transmissions of all kinds old and new over any young tech at the dealership who can’t wipe his ass without a diagnostic flow chart. You can poo poo experience - I tend to trust it.

 

[RichardSkinner]

Don’t modern transmissions have thermostatic bypass that don’t circulate oil through coolers until it comes up to operating temp? And diesel oil has what to do with transmissions?

They do, although people delete these to try to make their trans run cooler. ie 5th gen Ram 2500/3500 I know has an aftermarket thermostat delete kit available that advertises to run the trans down near 130F. However they don't talk about the fact that it now takes much longer to even get to that temp since it is an open loop when stone cold. That may not be a big deal in Sacramento during most months of the year, but in cold climates, over a lot of cold starts, that *could* be a mistake.

Without actually testing this stuff, or putting more effort into than this quick response, I can't say for certain whether it is significant, but it should be considered. That was all my disclaimer earlier about fully thinking through changing a designed coolant circuit.

 

[TaperPin]

They do, although people delete these to try to make their trans run cooler. ie 5th gen Ram 2500/3500 I know has an aftermarket thermostat delete kit available that advertises to run the trans down near 130F. However they don't talk about the fact that it now takes much longer to even get to that temp since it is an open loop when stone cold. That may not be a big deal in Sacramento during most months of the year, but in cold climates, over a lot of cold starts, that *could* be a mistake.

Without actually testing this stuff, or putting more effort into than this quick response, I can't say for certain whether it is significant, but it should be considered. That was all my disclaimer earlier about fully thinking through changing a designed coolant circuit.

I agree with you, if someone has poor judgement they shouldn’t mess with anything.

 

[displacedtexan]

If my 2025 transmission craps out I trust the old guys who have 30 years experience rebuilding transmissions of all kinds old and new over any young tech at the dealership who can’t wipe his ass without a diagnostic flow chart. You can poo poo experience - I tend to trust it.

I don't trust either of those groups.

Experience should also come with continuing to learn. It sadly frequently doesn't.

Modern transmissions are drastically different.