Huge rear end problem

[Goldmember]

There's a fill plug on the side of the tranny. Use it.
Going through the shifter is a PITA unless the tranny has already been out and the shifter is already out. Besides how are you going to know when it's full? or over full.
Pour in some fluid then climb under the car to see if it running out of the fill hole. Nope. repeat
Pour in some more fluid then climb under the car to see if it running out of the fill hole. Nope. repeat
Pour in some more fluid then climb under the car to see if it running out of the fill hole. Nope. repeat

Clean the pump you used to fill the rear end and use that for the tranny fluid.

I've always found the shifter method easier. Measuring isn't that hard... let me try to describe it... I have what looks like a Pyrex glass measuring cup with a tube on the end. On the tube is a valve that can stop the flow of the fluid while you measure. Then, undo the valve, let the fluid run out. I can have the shifter out in less than 10 mins. Just many ways to skin this cat. Cleaning that 75W140 out of the pump will take forever, stuff runs like maple syrup in 30 degree weather, lol...

 

[CC'S95GT]

I hear ya bout the maple syrup and 75-140
My luck, the bottle would bump something while filling the tranny and spill all over my seats and carpet.
Sometime I just have to outsmart my dumb ass and take precautions ahead of time.

 

[joekd]

I have filled all mustangs though the shifter and have never spilled a drop, here's what I do
-go to dollar store, buy a measuring cup
-fill it up with 1/2 quart (2 cups) at a time
-pour in through shifter
-lather, rinse, repeat
-throw away measuring cup