04gt 3650 Oil Change


Feb 13, 2004
I'm getting close to 10k miles, so it is probably past time to drain the trans fluid.

Castrol/valvoline/penzoil, etc Dex/Mercon III fluid ok?

and how much do i need? 4 quarts?
  • Sponsors (?)

StangPro said:
Factory fill is Mobil1.

Unless you use Royal Purple, Amsoil or Red Line you can almost expect to have shift problems or noise as the 3650 has some issues.

Fluid swap procedure here:


That's why i kinda say "If it ain't broke, don't fix it"

Some guys actually make their shifting problems worse by changing the fluid depending on what type they use.

I beleive '04 was the first year ford put Mobil 1 in there fromn the factory.

I should really do a fluid change myself...but you know what they say. "If it aint' broke....."
SilverGTV8 said:
I used royal purple ATF and have had no issues.

Ive been dealing with the notch 1-2 shift since my car was new, just last nite at 34k on the odo I finally swapped out the fluid and put in some royal purple, 4 qts. I know they changed the fill level to 3.2 but I think that was a band aid fix and would prefer to have it full. I was reluctannt to swap the fluid b/c I didnt think it woul actually improve the shift quality that much, well i was wrong. I never thought it would work so well. The tranny is much much quieter now, and the 1-2 shift quality is great. I didn't realize how loud my tranny was untill after the RP fluid. My recomendation is RP all the way well worth the cost and 40 mins to change it.
Been doing more research. Everything I've read or seen on the 3650 indicates that one is to use ATF in it: e.g.

- 2002 GT shop manual states Mercon Synth ATF
- this http://www.fcsdchemicalsandlubricants.com/fad/quickref/mantrans.pdf
- TSB 04-15-6

and so on. And people are putting synchromesh gear oils in (e.g. Royal Purple Syncro Max versus Royal Purple Max ATF) and getting better results??

Does anyone know Tremec's position on what fluid to run?
trinity_gt said:
Does anyone know Tremec's position on what fluid to run?

I called Tremec and talked to John, he said do not use GM Syncromesh (he did not mention RP Synco Max) because it swells the fiber material used in making the Synconizers in the 3650 transmission. He said use Mercon III / Dexron III at a quanity of 3.0 to 3.2 ltr. I now use Motorcraft MERCON ATF #XT-2-QDX but I could not bring myself to lower the fluid level from the specified 3.8L of the '03 owners manual to what he suggested. I did fill it to the 3.7L as specified in the '04 owners manual though.

He said the specified fluid of Mercon Synthetic or any synthetic, is too slippery and there is not enough friction for the syncronizers riding against the dog rings to get them up to speed to match gear engagement. That is why the TSB and the new '05 Manual states using Motorcraft MERCON ATF #XT-2-QDX fluid.