tluxon wrote:
60 degrees over ambient? Ha - maybe towing a pop-up on flat ground...
Our 2002 Burb has an instrument panel gauge for transmission temperature, but I use a scangauge which is considerably more responsive and accurate. On an 85°F day and towing our 8500-9000 pound TT on flat ground at average highway speeds, we'll see transmission fluid temps of about 160°F. On a long hard climb it's not uncommon to see the tranny temp get up to 220°F for short periods. Since that's about as high as I want to see it, it's extremely helpful to see just how long it's up there and how quickly it comes back down.
I'm afraid the built-in instrument panel gauge doesn't show the true temperature until damage would already have been done. I'd recommend something like the ScanGauge for anyone who's really serious about protecting their transmission.
Towing a 13K fifth wheel in 90-100 degree's. Highest I see is 185-190 on long mountain grades, 220 would trouble me.