Hi guys -- my truck has begun to chirp under load on acceleration. I immediately suspected the front drive shaft so I had it replaced with a new unit from Lucky8, but the chirp is still there, same as before.

It only happens in gear and under acceleration, at idle its perfectly quiet even if I rev the engine hard. It's also more pronounced when the truck is cold, and gets quieter as it warms up, but never actually goes away. It's also loudest when I first press the gas to accelerate.

I made a quick video of the noise while driving, it's hard to make out in the recording but it's there if you listen closely. This is after it quieted down after warming up:

https://streamable.com/ujbfc

It almost sounds like a belt or pulley, but why would it only happen under load? Ditto for a head gasket. Could it be the rear drive shaft? Any ideas?

 

I chased something similar on mine for a couple of months. Here is what I did to fix mine (which turned out to be multiple issues)

1. Replaced and greased front drive shaft
2. greased the rear drive shaft
3. Replaced both idler pulleys and the tensioner pulley
4. Found and fixed exhaust leaks by pressurizing the exhaust and using soapy water
5. Tightened a loose shock

one thing you might want to do is it pull the belt off and see if it still chirps. Also load up the driveshafts with grease to start.

 

It could be the gasket between the down pipe and the catalytic converter. I had a chirp sound on my disco under acceleration and at high RPMs as well. Immediately thought it was the front driveshaft, removed it, and the sound persisted. I later realized it was the drivers side down-pipe/ cat converter gasket. The composite gasket broke down a little and the airflow caused the gasket to vibrate and produce a loud high pitched chirp.

maybe if you re-torque those three down-pipe bolts on each side it will stop the sound.