Trans clunking while under load

[KyleBst264]

OK here's the update. The truck seems to be almost maxed out. It averages 9.3 MPG with this trailer. The trailer is a 20' enclosed car trailer, the toal weight of the trailer with the car in it is about 6,750 lbs. With the equalizer bars the suspension doesn't sag really much at all. The only problem is when I don't get a running start coming up to a hill the transmission makes a LOUD ping, I mean LOUD. The sound of metal hitting metal kinda sound. I checked the fluid and the u-joints and they're fine. I think my trans might be taking a little bit of a beating. Does anyone know what's going on here?

[robsawatsky]

Well, the electronics monitor slippage between the input and output shafts on the tranny and modulate the pump pressure if there is too much slip. This can make the tranny shift quite hard under certain conditions. It also means the fluid will be getting very hot from the slippage and likely indicates things going wrong or already wrong in the tranny.

 

On the other hand, I've never heard this described as quite the sound you are describing so it could be something else in the driveline that is getting whacked under load.