Humming noise coming from transmission when its in neutral. push the clutch in and it stops. suppose to be a new clutch also it runs great but if you lift the rear end off the ground the wheels will s

the clutch is dragging.
adjust the clutch cable, better is to replace it these cars
the cable goes bad inside (fray) and causes it to be the clutch from hell, get a new cable, or go nuts, saw 3 guys replace a clutch when its only the silly cable. bad. it must be set with free play.
the whole deal is here.
http://www.fixkick.com/tranny/clutch/clutch-on-kick.html

Check release bearing first

does the noise go when you push the clutch pedal down, if so its more than likely the springs in the clutch plate. replacement needed

SOUND LIKE FAULTY TRANSMISSION TORQUE CONVERTER CLUTCH SOLENOID.WHAT HAPPENING WHEN YOU COME TO A STOP.WHEN YOUR FOOT PRESS THE BRAKE PEDAL THE TRANSMISSION TORQUE CLUTCH SOLENOID SUPPOSE TO UNLOCK TORQUE CONVERTER TO KEEP FROM STALLING THE ENGINE IF NOT THATS WHAT CAUSING THE ENGINE TO STALL OUT.SO HAVE THE BRAKE LIGHT SWITCH CHECK OUT AND HAVE THE TRANSMISSION SCANNED FOR A TRANSMISSION TORQUE CONVERTER CLUTCH SOLENOID FAULT.

No, By pushing in the clutch to stop the hum all you are stopping from turning is the transmission and ( transfur case if 4 wheel drive ) the engine is still running ..and some parts in the rear differential . I have had 4 nissan pickups and currently drive a 1995 pickup, without actually hearing the noise I would look toward the transmission, these Manual transmissions are very prone to bearing failure. This has happened to 2 of the one's I have had including the one I have now. You can also see as time goes by if the noise is quieter in fourth gear than others because this is direct drive and not as many trans bearings are involved Good Luck

A couple of things comes to mind, when you press the clutch you disengage the transmission. When the clutch is not pressed the transmission still spins inside even when it is in neutral. Sounds like a bearing inside the transmission is making noise, did they put fluid back in the transmission? Also another common source of noise is the throw out bearing, it is on the input shaft, it is the actual part that presses against the clutch pressure plate, usually though they make noise when the clutch is pressed and quiet down when released.

this sounds like a bad clutch throwout bearing in tranny. if it makes a rattling noise then its the bearing. when clutch pedal is pushed in.

If the truck was ran low on fluid to the point it clangs and bangs, the internal damage is done.
The best you can hope for is burnt bearings and hopefully the shafts are not scored. Disassembly is the only solution. Or a used transmission.

You need a new throwout bearing in your clutch assembly.

The problem is probably not the throwout bearing. Noise from throwout bearings act just the opposite, you only hear them when you push in the clutch pedal. Noise when the clutch pedal is released only is either a bad pilot bearing (probably oilite bushing) (the bearing/bushing in the middle of the flywheel that supports the transmission input shaft), or bad transmission bearings (will happen sometimes but is unlikely because in neutral, with the clutch pedal released, tranny bearings spin, but are not really under any load, but in some cases they might be the cause of the noise anyway)