I have a 2005 Chevrolet Suburban 4WD 5.3 (208k miles) that has several loud taps when I accelerate moderately to hard. It only happens from slow or stop. I haven't been able to get the sound when flooring it after 20 mph. The sound is coming what sounds like directly below the cab or a little forward. Can't isolate which side and don't see anything obvious underneath. I power braked (in gear, holding brake) and was able to get it to happen once. Only happens when in drive. Happens in 4 low also.

Here is the video of it. I accelerate on 2 occasions and you can hear it at 3 seconds and 17 seconds,

Any ideas what it could be?

I have a 2005 Chevrolet Suburban 4WD 5.3 (208k miles) that has several loud taps when I accelerate moderately to hard. It only happens from slow or stop. I haven't been able to get the sound when flooring it after 20 mph. The sound is coming what sounds like directly below the cab or a little forward. Can't isolate which side and don't see anything obvious underneath. I power braked (in gear, holding brake) and was able to get it to happen once. Only happens when in drive. Happens in 4 low also.

Here is the video of it. I accelerate on 2 occasions and you can hear it at 3 seconds and 17 seconds,

Any ideas what it could be?

EDIT: Not sure if this has any bearing on it but when inspecting ujoints, saw this on transfer case output to rear