I have a 2008 F250 5.4 L with a 5R110W transmission. Had a shifting issue and I added about 400 ml of Mercon SP and it cured the issue....I think. Some background first. I bought the truck used and when I got it the transmission filler tube/dipstick tube was rusted out. The first time I put the dipstick back in it came out the side of the tube. Anyway I could not get a used one at a local scrap yard so I cut out the rusted portion and added a new piece in. I got the lengths as close as I could. Might be off a bit but not likely more than 1/4 inch. But the problem lies in the piece I added. It is a bigger diameter than the original tube. It slides over the tube. That means when I add fluid there is residual in that section and it goes on the dipstick when I insert it. If the rusted portion had been on anything but the horizontal section by the exhaust manifold I would have no problem. All the fluid would simply drain into the tranny.

So here is the question. What is the range in ml from being underfilled to being overfilled? Obviously I was underfilled before adding the 400 ml but it would seem to me that a transmission that holds about 16.5 litres would have a range higher than just 400 ml. I can add more and guarantee I am not underfilled but I do not want to be overfilled either. Not likely a problem too many have run into but if someone knows a number I would appreciate it.

In an event I will be shopping next week for a new filler tube.

 

Trans fluid expands when heated and overfilling the 5R will cause damage. Furthermore you can't just guesstimate its fluid levels. I'd get the new (or used) filler tube (relatively straightforward install) and get the truck baselined so you can correctly check hot and cold levels.

 

Thanks for the reply. The new filler tube is the correct answer. I never really even thought about fluid laying in the low spot when I was doing the repair. Did not really phrase the question very well. What I should have asked was what how much fluid can be added to raise the level from the hot low level line on the dipstick to the hot max level line on the dipstick.