Trans fluid capacity

What the book say is fine, as are all the suggestions you get here. The safest thing to do, is put in the amount you took out.

The book states four gallons following a disassembly which would include the torque convertor. I was able to get three gallons out doing a cold drain and pushing oil out of the cooler using compressed air at the frame rail filter. The remaining gallon was probably the convertor.

Forgot to add, use a five gallon bucket pre-marked with lines indicating each quart. Only refill with the amount you take out. This was my first change but second for the coach. Not sure what the prior owner used but the up and down shifts do feel a bit smoother and much less down shifting on low hills. I used Motorcraft Mercon SP XT and only replaced the external filter.

Check your dipstick cold before you drain and fill it to that same level. This should be a good place to start. Then warm up the transmission and verify the correct level by checking your dipstick as recommended when the fluid is hot.

I would try and measure the amount you can drain out. I did a trans service and replaced the amount stated, it was a good quart over full.

10-12 quarts not including converter.