engine making grinding noise

Definitely sounds like a lubrication problem.  Try cleaning the motor gears and re-lubricating.  Dry gears will make that sound.

If it's sat a long time the old grease in it could be hard and absolutely useless. Time to go in!

Hi, RKenney, Jeff T, i just tried all that, took it apart, cleaned off All old grease, none of which was dried out, tested each truck, they run fine unassembled,  it only makes noise when assembled and engine shell is back on, only difference is it doeasen`t slow down like before, but still grinding, thank you so much for your help, Phil

Check worm drive gear carefully.  If this is a DCS model with can motor, you can be grinding up the gears and it will be a time for new ones. Can be motor alignment issue.  G

Hi, GGG, it`s not a DCS model, it`s a an old Lionel Standard gauge 402 with 2 super motors, thank you , Phil

I would put ONE drop of oil on each of the drive axle bearings.  Also on each end of the armature shaft, and the intermediate gear shafts.  Rock the wheels back and forth by hand if possible to work the oil into the bearings.  Hopefully that will get your venerable loco running smoothly again!

Good morning  Ted S and to everyone who helped,  it turns out i missed putting grease on one gear where three of them work together, i did that, ran it around the layout slowly for ten minutes, now, at higher speeds, she runs like a champ pulling her 4 cars with no trouble at all, with no grinding  noise at all, thank you all so much for your help, Phil