Taking a Deeper Look at Transmission Overheating in 4Hi

[JustDSM]

Hey everyone,

We’ve been following the discussions around transmission overheating—particularly when operating in 4Hi—as highlighted in these threads and others:

• 2024 Tacoma Transmission Overheating on Long Climbs Off-Road
• Transmission Overheating in 4Hi When Going Uphill – Toyota’s Answer (or Non-Answer)
• 2025 4Runner Transmission Overheating on Climbs Off-Road

We (OTT) want to take a deeper dive into this issue, as it’s clearly affecting a number of owners in the community. While adding a transmission cooler is certainly one part of the equation, we’re also exploring whether software-oriented changes could provide a meaningful improvement or potential "fix".

We've been evaluating some changes behind the scenes, but we'd like to better understand where/how this happened to you. As such, we’d love to gather more real-world data from those of you who have personally experienced the overheat condition in 4Hi (or 2Hi if applicable). If you’re willing to share, the following details would be extremely helpful:

• Transfer Case: 2Hi, 4Hi, or 4Lo
• Transmission Shifter Position: “D” or manual selection (S1, S2, S3, etc.)
• Drive Mode: Normal, Eco, Sport, etc.
• Vehicle Speed: An average speed is great, but more detail like “~15 mph most of the time, varying from 5–20 mph depending on terrain” is even better.
• Duration: Approximately how long you were operating in that state before the overheat occurred.
• Additional Weight: Estimate of weight over stock (aftermarket gear, camping equipment, etc.) present at the time.
• Tire Size: If different than OE.
• Transmission Cooler: Fitted Y/N.
• Other Details: Anything else you think is relevant or noteworthy.

The more detail the better—we want to look for common threads and contributing factors.

Thank you in advance for helping us compile this information. We’re optimistic that with sufficient community feedback, we can gain a deeper understanding of the problem and explore a comprehensive solution that extends beyond just hardware.


—OTT

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[Vidman]

So great that OTT is looking to possibly sort out the trans overheating issue.. that would be a game changer for the people that have had issues. I have had no issues as of yet so I cannot contribute any info at this time good luck getting something in one of your tunes that will solve the problem..