roegs

Not sure why you guys all say to fill to the fill hole. Both Ford and Tremec say to fill to 1/2 inch below the fill hole. Ford says it in the shop manual and user manual. Tremec says it in their shop manual for the 3650. The reason is described the end of this article.

http://www.rsgear.com/articles/2007_08.pdf

Diabolical!

That same sentence says to use Dextron III ATF, which performs like garbage compared to most alternative options. Different versions of the Ford manual and Tremec manuals for the 3650 say it both ways. Half say 1/2" below, the other half say to the fill hole. To the fill hole is easier and hasn't caused me any issues.

roegs

The newer versions of both Ford and Tremec documentation all say 1/2 inch below the fill plug. If you read them, they clearly say not to fill to the top. Even my 2009 owners manual clearly says not to fill to the top. Both Ford and Tremec have changed their position since the early models due to problems they had with too much oil. I'm sure many of you will run just fine with it to the top of the fill plug, but the correct answer to the OP's question is 1/2 inch below the plug.

moosestang

I just filled till I could feel the oil with my pinky finger. That was 4-5 years ago. I should probably change it again, but I'm only averaging 6-7,000 miles a year.

157dB

I added the OEM stated fill capacity and it came to just below the fill hole.
There must have been some residual fluid that didnt drain when
I changed it.
I dont see any difference between 1/2 below and just below...
But then my rear diff level was OEM stated to be 1/2' below then a
TSB came out to fill the 7.5" to just below the fill.
Maybe thats whey my rear axle bearings went south at 30K miles and
had to be replaced...

Goldenpony

Thanks everybody. I filled my 5 speed with Amsoil ATF to a hair less than 1/2" below the fill hole. I'm sure this will be fine.