Clunk when downshifting pulling trailer

Our home lies in the mountains at the end of a moderate-grade long uphill pull and then a steep-grade short uphill pull. After arriving home with the RV I merely shut the engine off. Perhaps the transmission is hot after pulling these grades to our house and I should be idling the engine for a few minutes after arriving home to cool the transmissions down?

I don't know if it is related to the damage, but I had a similar thing happen to me last summer. Pulled into a scenic overlook after a long uphill grade. Stopped, looked at scenery-a textbook hot soak. When I pulled out the clutch fan hung on and on.. and held on to higher RPM for a very long time. The drivetrain had accumulated a lot of heat... I thought at the time in the future I'll idle it like a turbo engine after a pull like that.