Excessive Vibration

Hi I am a s10 owner and lately have had a few problems with an excessive vibration from what feels like is directly underneath the cab and roars alomost like going down a level B road or almost if not shudders as well. Now this only happens when I am accelerating. I let off the gas it stays for 1 second consistently every time i try. and then completely disappears and the truck is a rolling without any vibration at all. Hit the gas again and rororororoor the vibration comes back and the roaring . It feels like the ass end but it also feels like its right underneath the drivers seat. If I let truck roll at any speed in neutral it wont do it, but when I give enough gas it comes back. When in park it does not. when not moving in neutral and give it gas there is nothing, only when moving. I just changed diff fluid and cleaned up the drum brakes and both sides need replaced , I just haven't had the cash. Tires are A1, Truck runs great and transmission is iffy if not in rough shape. I have no trans dipstick either as I need to find someone with one so I could check that. Just bought trans filter and fluid and gasket, going to change that tomorrow, a friend says fill it until the manufactured recommended amount is in and call it a day but i would still like a reading. Other than that I don't want a $100.00 bill for somebody's time and opinion at a local shop and would love some help on here. I am a tinkerer and a garage nut but more so towards making sawdust not horsepower so give it to me simple and Thank you for reading

Specs: Chevrolet S10 2003 base model 2.2 liter rear wheel drive. automatic trans.

It does appear you are in very bad shape $$$... This is a good vehicle for you to learn about auto repair then you will have more $$$ and buy a vehicle that will operate properly.

the S10 you have now should be in the scrap yard.

you start spending $$$ on that vehicle , you will not have $$$ for your other bills.

I would suspect tranny and/or u-joints.