Fellow Mustang Owners,

Time to set up for 20,000 mile service. Mobil1 5w-20 check, FL-820s check, inspect brakes and bleed DOT3 check, At this time I thought I'll change fluid in transmission. I know it has been a sticking point about what to put in the TR-3650, the amount of Mercon, Mercon V, Mobil1, Royal Purlpe, GM Syncro-Mesh or theany other flavor.

Mercon seems to be the choice but Mercon V lately seems to be the choice. I emailed Tremec and just got back a stock email telling me to follow guidelines ofcar builder.

So what is it? fill to 1/2" below?, level, moreor less? and with what? I have just about talked myself into Mercon V but have read synthetic is not good for theTr3650.

 

RP 1/2 inch below

 

+1

 

As an FYI - Don't mix any GM transmission fluid with Ford transmission fluid. My dad had a guy in his college auto shop class that putFord transmission fluidinto his Chevy's transmission, and the residue in the tranny created a horrible sludge. I know that they don't mix, so if Ford recommends putting Mercon V into your T-3650 tranny, I'd definitely go with that...

 

+3

 

I filled mine 21k ago with Redline D4 and a 10% mix of Tufoil. I filled it up to the rim, with fluid running out, I had it on ramps, so not flat to the ground. I was under it Saturday with 25k oil change, trans looked dry as a bone, has given me no issues.

I've moved to NC, Redline not readily available here. Saturday's oil change was with Amsoil. Will change out the trans next time at 30k, Redline feels a 30k cycle on the transmission fluids is not a bad idea. Will be using Amsoil.

FWIW, Been using Redline for many years. When starting up the GT I'd get a wee bit of tappet noise for a wee bit of time. Saturday I put in Amsoil 0w-20, sucker is quiet as a mouse, I really think it runs quiter all the time.