F150 2004 truck 4X4 the rear end has gear metal in the oil

Get codes read first then if needed by code check wires continuity for breaks in the circuit

The only place to put gear oil is in the "pumpkin". Otherwise called the rear-end.
To do so, I recommend driving the car backwards onto two ramps to raise the rear end up in the air, this also tilts the car forward.
Between the rear wheels, in the center of the axle, is a large metal container of gears and gear oil.
There should be a large hex-headed bolt less than half-way from the bottom to the top on the rear, facing your back bumper.
This is where the gear oil goes in, but after you take the bolt out, before you add any oil, stick your finger into the hole and try to feel the oil level.
If you can feel it, you don't need any more gear oil to be added.

put high quality gear oil in the metal filler cap on the rear end if that dont work it could be that your rear end is shot

Check your u-joints first. If it is not the u-joint, then it is probably the yoke. Take the driveshaft off/out and on the yoke you will see a nut, make sure that it is tight. You will want to drain and refill your rear end gear oil as well.

you can use the oil for the towing package in either rear end, but what they want to know is if the rear end is posi track. to find out jack up the back of the jeep put the transmission in neutral and turn one of the rear wheel if the wheel on the other side turns in the same direction that you are turning the wheel then you have posi track if the wheel on the other side turns backwards the you don't. but like i said you can use the towing oil in either rear end when in dought use the towing oil.

It could be bad pinion bearings, broken spider gears, etc. inside the differential. It could also be an axle bearing. Check the insides of your rear wheels to see if there is any rear-end grease coming out near the wheel end of the axle. If there is oil coming out, then you have a bad wheel bearing. Otherwise, you will have to remove the differential cover to check for metal particles in the rear end and to see if there are any broken gears.

90w gear oil but i go to any truck stop and use power punch to me it lubes better then most gear oils only oil i can think of thats better then that is lucas

A pinion seal leaks for one or boyh of these reasons. A worn pinion bearing or a driveshaft vibration, Sounds as though you have both. Do not confuse tire howl with gear howl, be sure.The rear end can run 3 to 500.00 if not more. Ck the gear oil in the rearend for metal content. That will tell you alot. The hard shifting is generally from a sticky spool in the trans valve body. Have the trans serviced w/new oil and filter. The new oil often cleans the moving parts of gum and varnish buildup.in the valve body. One more thing, the rear ends take a special oil and additive if it's a limited slip or posi lock. You will have a popping/binding noise when turning if the wrong lube is install. Have your driveshaft aligned and balanced at at driveshaft shop.or you will end up tearing up the tailshaft on the trans. Good Luck

That's fine it uses 80w 90 . 75w90 will mix

drain the fluid, take the old seal off clean where the old seal was with some brake cleaner. replace seal with a new one or the gasket sealer in a tube spread evenly put cover back on fill back up with gear oil up to the hole in the rear end