I’ve had a overheating trans issue before and I swapped this trans a few months ago and now I’m having the same issue again kinda.
Maybe i overfilled it a tad last service and it averages like 210 after a long freeway drive.

 

The LS430 uses a trans fluid cooler/heater in the bottom of the radiator that is immersed in coolant.
Once warmed up (temp gauge in the middle) the coolant and trans fluid will be at 195-220F. That is the normal range.
What made you think your trans was overheating?

When did you last change out the radiator?
The LS430 has a known issue where the trans cooler corrodes and lets coolant mix with the trans fluid, which destroys the transmission.
I had a new radiator at 150k miles. The old one was still fine but rust had started.

 

that’s not a bad idea to start with cause I was planning on getting a external trans cooler but usually around 220 it shifts weird in stop and go traffic and I can tell there’s a power loss for sure in low end. Maybe it’s not a bad idea to do the radiator but I was already planning on getting a external cooler

 

I am not a mechanic or familiar, but if yo do get external cooler, probably route around the internal radiatot completely to avoid the risk bigboomer was talking about. I am still on my original radiator at 170k miles (2005) but now I am getting nervous.

 

[QUOTE=SoilTheCadaver;12052404]I’ve had a overheating trans issue before and I swapped this trans a few months ago and now I’m having the same issue again kinda.
Maybe i overfilled it a tad last service and it averages like 210 after a long freeway drive.
[QUOTE]

You replaced a transmission because you thought it was running hot?
What scan tool are you using to get these temp readings? Are you sure your tool is accurate..? Is the trans filled with the correct ATF?
Is your radiator healthy? Thermostat healthy..?
If your cooling system is compromised, nothing you do to the transmission will fix that.
The radiator issue Boomer mentions has been known to happen on some high-mileage Toyota trucks, but it's rare on an LS.
Adding an external cooler will not fix your issue; there's an underlying root cause problem that needs to be identified and addressed.

 

[QUOTE=bradland;12052693][QUOTE=SoilTheCadaver;12052404]I’ve had a overheating trans issue before and I swapped this trans a few months ago and now I’m having the same issue again kinda.
Maybe i overfilled it a tad last service and it averages like 210 after a long freeway drive.


torque converter seal blew on the previous trans and I’m not gonna keep one that’s been overheated multiple times lmao.

and I have multiple scan tools and a $300 dollar one that I’m positive it’s accurate.
i just put a colder temp thermostat and new fluid in cause previous owner put straight water in it smh
will see what happens now with the temps

 

I would strongly advise against doing this.
You're not going to build a better or more efficient mousetrap than the Toyota engineers.
The 1990 to 2006 LS cooling system is damn near perfect.

 

If you are getting temps into the 240s then your coolant is also getting too hot, so maybe have a look at that first.
If the Thermostat that you had was non-standard then that could explain it. Definitely fit an OEM Thermostat.
As for the radiator, I have only heard of 2 or 3 LS430s where coolant got into the trans fluid, so it's rare.
The only problem with running a separate trans cooler is that in winter you will overcool the trans fluid.
The ideal system is to get everything back to OEM, and perhaps consider replacing the radiator with a new one.