My '05 Yukon begins pinging/clanging loudly from the undercarriage (possibly the muffler) after driving for about 10 minutes. After driving, the pinging continues for some length of time, depending on how long I was driving.
I live in the south and the problem began a couple of months after a winter trip to Chicago, complete with snow, ice and salt, and I failed to wash the undercarriage when arriving back home. There are some rust “freckles” on the frame and axle, but nothing on the muffler; the drive shaft is completely covered in rust. Could rust be the issue?
If rust was the issue…then all vehicles here in the North East would have this problem.
It doesn’t sound serious…Without hearing the sound it’s difficult to diagnose. If it is the muffler/exhaust then something might be loose (like the heat shield around cat).
As Mike suggets, a heat shield is making the noise from heat expansion and contraction.
Since the noise is new and you say you haven’t cleaned well under there, look for trapped debris between shields and Exhaust components and clean that out. It’s probably transmitting the heat which it didn’t before when it was clean there.
Would the truck make the noise if ruuning up on a hoist ?
This would allow you to investigate as the noises occur and narrow down the culprit shield to clean ot tighten.