grinding sometimes when I accelerate.??

Hello fellow brothers and sisters.
first I would like to give a gracious thank you to all that assisted in helping me replace the front rotors .

Now for the new trouble , 2 weeks ago , ! heard a grinding type noise while accelerating from 5-10mph and it went away within 5 seconds.

later that afternoon again around 25-35 mph , it did it 3-4 times 5-10 seconds. seems like a grinding type of noise gggrrr and goes away .

no other troubles for that week , now this week I heard it a little bit when I started the truck , it had been sitting for 6 days. I drove it for about 3 blocks and it came and went but only when I gave it gas

if I took my foot of the gas when it would start making the gggrrr it would go away..

what could it be ??

ps. no bad indications on dash

please advise
respectfully
SteveThere were about 4 -5 rotted clamps around the exhaust heat shields, replaced all noise gone .

I have a 95 pathinder with a related (?) problem:
In the low foward gears (or perhaps just first) there is a subtle chatter sound, as if not fully engaged. And when moving there also is a strong grind as if wheels scraping, but when the car upshifts this noise goes away. Additionally, when in Park, Neutral, Reverse, the same chatter noise, as if not fully engaged, or perhaps not properly released from another gear, is striking. These noises are consistent since they started. Sometime when just starting up and putting in gear, D or R, the car stalls unless I quickly hit the gas to make the car move, which eleviates the danger of stalling.

Any help is appreciated.