I searched alot on this subject but mostly all I can find are 10 year old threads/post. What is the lastest info on what oil is ok for the 3650? I know that ATF was originally recomended, but some used GM MTF with good results, but some experts say that synthetic oils in time ruin the syncros in the 3650. I have used Amsoil MTF 5-30 in my transmissions other than Ford with excellent results,----What is the latest info and/or most popular being used now.

 

It came with Mercon-the updated ATF recommendation is Mercon V,and that's in mine now.

 

Mercon V, and its about 4qts to full if you drain it completely...do not top off until it spill out the fill plug like you would any other manual trans..

 

One thing I know for sure after reading a ton of post, the tremec 3650 gets filled with 3.2 qts and yes that is below the fill hole. It uesd to be 3.8 qts to the fill hole but that was causing shift (sycro)problems and ford and tremec started recomending 3.2 qts about 11 years ago (for the 3650). The majority of post that I have read are using Mobile1 atf. Also the majority say dont use snycromesh or other synthetic gear oils.

 

Isn't Mobil1 ATF synthetic?
A fluid change isn't something that's going to be done too many times,though I think that it's a good idea.Did mine in the mid 60ks.
Rather than try to get the car raised and level,I drained the trans,pulled the shifter,and poured 3.2 quarts in the top.

 

Yes mobile1 is synthetic but its automatic transmission fluid not gear oil. From what I have read the synthetic gear oil has a high sulfur content and that in time is what ruins the syncros in the 3650 because the 3650 has fiber composite syncros and the sulfur degrades them. From what I read many people have been happy with GM syncromesh mtf and other snythetic gear oils, they say the tranny really shifts smooth with them but over time it ruins the syncros.

 

run mercon V, the end lol

 

Mobile1 ATF meets or exceeds the requirements of MerconV.
https://mobiloil.com/en/automatic-tr.../synthetic-atf


Here is an interesting thread from another forum and the secret sauce thing is funny.
http://www.moddedmustangs.com/forums...nny-fluid.html