How do i put the oil in dierential 1983 - 1983 Ford Mustang Hatchback

There's a plug on the side of the trans you need to take out that is the proper level. That's where you put the oil in and when it won't take any more and runs out same hole, put the plug back in and done.

put engine flush in it first till oil hot then drain it,change the oil filter.and refill with 20/40 oil.

Your 1983 Toyota Celica takes 4 quarts with new filter,Since your just adding,it depends what is showing on the dip stick,you say it's real low,which it probaly will take a least a quart,then add that and wait a few minutes to get to oil pan,then check dip stick twice and if still low,open another quart and add a fourth and check,add more if needed,then after you have drove,park,let sit,then check.If you add to much,there's a drain plug at oil pan underneath,You can go to Autozone and buy oil and ask if they will add,they will do it for free.

for better result download the pdf file
Toyota Tercel 1983 1998 Workshop Service repair manual

It depends on which rear end is in your truck. There may be a plug about half way up the back cover on the differential, or it may be on the front passenger side of the rear end. The plug will come out using a 3/8 drive ratchet. Make sure you use a screwdriver or something to clean the hole out before you try to turn it. If you don't get it clean then the ratchet will slip and round the corners of the plug and then it isn't coming out.
Add your oil until it starts to leak out the plug hole. Then it is full and put the plug back in. You need to know if you have a limited slip differential or not. Limited slip takes special oil. Regular rear ends take 80-90 gear oil. Hope this helps.

just fill it up till the top mark on the indicatorstick.

either renew the oil pump or try a tin of STP oil treatment

i hate to say it but... i recommend pulling the engine out and putting it on an engine stand. while it is out replace crank seals and inspect freeze plugs.

I've had the same problem with my 22r.
I just put silicone gasket ( the stuff you get in the tube for automotive) on top of the o-ring.
It added an extra seal plus also hold the o-ring in place when putting the oil pump back on.
Never had a problem with the oil pump after that.

there is no oil up in the intake area so its nothing you could have done BUT the oil pressure reading comes from the oil pressure sending unit near the dist. housing. you had to remove the dist. when changing the intake so maybe the sensor or it's connection are loose.
good luck chris