At 104F my rig sees 194 to 196 hauling a trailer at low (sub 30 mph) speeds.
Before I changed to the blue hub clutch (unmodifed) I was getting 226+.
If I lived in Death Valley, I might put some different Silicon Oil in it, but here in SC where it only gets to 100F once in while, I'll just leave it stock. Its working fine.
Dude! Just put the frigging thing in your truck and run it... don't mess with what ain't broke.
If you choose to F with it, you'll need one of these:
Order today, ships today. FLK-T3000FC – Handheld -200 ~ 1372°C Thermocouple Thermometer LCD C° Backlight, Memory from Fluke Electronics. Pricing and Availability on millions of electronic components from Digi-Key Electronics.
www.digikey.com
Or just bite the bullet and get one of these, everybody needs a multimeter anyway.
Order Fluke Industrial Digital Multimeter, 1000V, 10A, FLUKE 87V/IMSK at Zoro.com. Great prices & free shipping on orders over $50 when you sign in or sign up for an account.
www.zoro.com