auto vs manual could be different, i thought the diff's just had a allen bolt that comes out and you fill into the diff itself. i don't have a differential dip stick
Rear diffs have the 2 square inset bolts, one for draining it and one to fill. The upper fill hole is also the fill level.
Front diffs have a drain plug and a dipstick. The dipstick hole is how you fill it. Doesn't matter if it's manual or auto, you have a dipstick in your front diff. If you don't have one then it's missing.