I had OBD Fusion connected for the recent Kentucky Toyota Trail Ride as I wanted to get a feel for these readings on and off road. Here are screenshots from various times and the overall takeaway is that Toyota did a fine job designing a system that keeps everything relatively cool.
Trail driving (except the gravel sections) was done in L, 2, or 3 as appropriate. These are in time stamp order. You can see altitude changes and our coordinates if you wish to map our exact position, and the intake temp shows that it was a hot one yesterday. There were rocks, streams, climbs, steep crawl descents, and mud. For example, this 5th Gen needed some help and reached the top minus some lower front end body parts and with a bent step rail.
Not saying these were black diamond trails but it sure wasn't gravel cruising either.
This is at 0915 in the group lineup before leaving Callie's Campground for the trails:
On the trails (numbers are times):
1108
1227
1442
1520
1545
You get the idea - the tranny oil temps stay pretty reasonable on the trail.
Here's the odd part: I've had this hooked up in the past without taking screenshots and only saw the ATF temp get close to 200F a couple of times. So I was surprised when the reading at the TC rose to about 225 on the way to the trails. We were still on pavement and climbing a moderate incline. Gear selection was the usual 4D.
I didn't get a screenshot then but stopped by Cumberland Gap National Park on the way home and noticed the same thing while driving up to Pinnacle Overlook. Here's a screenshot from the top:
(Ignore the green/yellow/red arcs as I have redone them since learning last night that the A/T OIL TEMP dash light doesn't come on until 275F per the FSM.)
What was very interesting is that the temp began dropping whenever I changed from 4D to using whatever gear (2/3/4) seemed best for the section I was on. (I drove a stick for 17 years so I have a good sense of what gears to use.) I only know the basics of how transmissions work so I watched a video on torque converters to try and understand why that happened but still have a question:
Does driving in a specific gear bypass or disengage the torque converter? That's the only reason I can think of for the oil temp to stabilize then decrease when I shifted directly.
Also, on a semi-related note:
If there's a PID for oil temps in the transfer case and/or diffs, I missed it. Anyone know if there are sensors there and/or how to do an associated PID?
Thanks for any insight.