Hello I have a 1995 GMC Jimmy (Automatic & 4x4)and I have been working on it on and off for about a year and a half, i have fixed many things with it but there are couple things that I have not been to identify and fix

Possible Engine Knock:
When the car is first over I can hear a engine knock or more accuratley a "chugging" sound that causes a lot of vibration in the car. The Feeling is felt worse in drive and lesser in the reverse and Park gears. The sound goes away one the car is out of idle as well

I have replaced all the spark plugs, plug wires, distributer cap. As well as the head and intake gaskets and the fuel injection system. What do you think is causing this? (I will reply if more information is needed) (I have also checked the motor oil levels already)

Second issue:
When first accelerating from stop i hear a shallow grinding type sound coming from my car (that'* the best way to describe it), but it quickly goes away once the car gets up to speed around 40 - 50 mph. What do you think this could be? I have not much transmission work on the vehicle so could it be a transmission issue? (yes I have checked the fluid levels as well)

Sorry for the long post, but thank you for your consideration!