What is a normal temp, and what is too hot? I'm towing near the max.
After getting home i IR gunned the black diff cover, it was 215F The last 5-8 miles were at 45mph or so, ran an hour at 65mph, then the last 5-8 miles at 45, so would it have cooled much in the last few miles? Ambient temp 94F.
Is that too hot? My rear has 85-140 non syn. Will that heat damage the gasket? It has a lock right locker.
"normal" depends on the fluid specifications but more importantly on the accuracy of the temp.
OEM's of fluid give you the temps of their product as determined in a sump in the middle ( as per most process requirements in industry)
The skin temp of the diff taken with an IR gun without knowing the emissivity and range and location of the surface temp ( as well as the condition) is not an accurate indicator of the actual core fluid temp.
Also, a working fluid ( normally thinned and aerated) has to settle to get a correct static temperature.
This is a semi complex science on heat transfer and accurate measuring but you would be more accurate in actual fluid temp to get a VOM with a K type probe and stick it in the fluid center after about 10 minutes setting (fluid setting) still rather than relying on a skin temperature for raw data.
The other part is there is more than one correct answer to normal ( or acceptable) because each component ( seals, bearings, gears, gaskets) each have different thresholds of what is and is not acceptable and ranges of exceeding them.
In general 100F above ambient is a good average but then that's the fluid, not the skin so to be accurate there needs to be correlation factors
Just advice for those who really intend to use these numbers- the first step is to ensure the accuracy of them.
