Just changed the clutch in my 2003 Kia Rio LS limited now when i put it into 5 gear there is a whinning noise. the noise is worse in reverse as 5 gear and reverse run off the same idle gear. Now does the diff has its own filler hole or does it have the same filler hole as the gearbox. i lost about 2 litres of oil when i had to take the drive shafts off and the olny filler hole i could find is on top of the box. is there another way that i can pit oil in it or is that the only way. regards.

Time for a rebuild or replace. Clutches burnt, bands worn out , torque converter whining or worse, planetary gears.

Can you put it in gear with engine off? If so, you have a problem with your clutch.

The clutch system in the Kia rios of those years are clutch cables, not hydraulic. There is no need for clutch fluid. Have a mechanic look at your clutch cable tension.
If it turns out to be a tranny prob thank Korea for building cheap cars.

Have some one ( with engine OFF) slowly shift from 1st to Reverse, YOU be out side and watch the linkage and tranny movement. WHAT you may have is loose bracket, tranny, or support bolts. bigAl

what would happen if you put it in first gear,put your foot on the clutch then try to start the car....of course pick a place where safe!!!...if it rolls forward while cranking ,the clutch plate is touching the flywheel (in other words the clutch all the way down while in gear while cranking,should NOT touch the flywheel(transmission part that makes the car move) so if it moves then it shows the transmission reacts to the clutch touching the other jiggamathig. Possibly clutch system needs bleeding (air in the hydraulic system). I'm sure your car has this thing called a "clutch slave cylinder". Now,this is one thing I would check first.

synconizers or shift fork bent, but most likely your throw out bearing is not dissengageing your pressure plate al the way. check your clutch linkage.

I would check the operation of the shifter cable. It may need lubricated.

check level of fluid at reservoir ,might need bled,  check for obstructions near pedal(floor mats,etc.)

That is what happens when you try to shift gear with out depressing the clutch pedal while changing gears.

I agree, I believe it is your release bearing. Your clutch might be going out.