Mercon tranny fluid discontinued - what's everybody using

[Buzzystang]

This TSB kind of went unnoticed, seems like. Ford is discontinuing licensing of the Mercon spec and recommending use of Mercon V in most applications, including the 2007 Mustang.

I looked on the Tremec FAQs and they now recommend "Dexron III" and have dropped the "Dexron III/Mercon" recommendation.

Dexron III is still being licensed by GM for the time being, but I read that GM will eventually drop it too, like Ford, to a fully synthetic spec.

So, what to do...buy up a bunch of NOS Mercon? I've made trips to Pep Boys, AutoZone and Wally World and have come up short. Pep Boy's had a Pennzoil and Wal-Mart had a house brand backwards compatible ATF to the Dexron III/Mercon spec...not sure I'm keen on using either of those brands, but I'm running out of options.

I've been using RP Synchromax in my 3650 the last six months, but have noticed in the Arizona heat that it is starting to get really noisy and turning into a rock box. I think for my application, a non-synthetic Dexron III fluid as Tremec recommends is my next/best option.

 

[travelers]

So is there a reason you don't want to change over to what Ford is recommending? They must have a reason for the change.

 

[redbullet]

GM Syncromesh pt# 12345349 and add Fords friction modifier LX 3 or GM Synchromesh FM #12377916 which has a friction modifier in it.

Pennzoil, Texaco, Quacker State all bottle the same stuff under license from GM.

I know, it's a GM part, just do a search and you'll see.

 

[Buzzystang]

So is there a reason you don't want to change over to what Ford is recommending? They must have a reason for the change.

The new spec is fully synthetic. Tremec recommends non-synthetic. I would like to try non-synth to see if it performs better in the hot dry heat of Arizona compared to my experience with synthetic.

 

[redbullet]

Mercon V is for the electronically controlled transmissions. Some of the parts internal to the trans, like the solenoids, use precious metal on the contacts and the old style fluid would corrode them.

In the past I found the substituting RP trans fluid in auto's for the Mercon V resulted in problems after a few thousand miles of use.

 

[rog06gt]

Changed the oil at 22000 miles with Mobil 1 ATF now have 29000, no issues whatsoever, as a matter of fact the tranny is a little bit easier to shift... 3.2 quarts or 1/2" below fill hole.
Cheers

 

[Royb]

.......
I've been using RP Synchromax in my 3650 the last six months, but have noticed in the Arizona heat that it is starting to get really noisy and turning into a rock box. I think for my application, a non-synthetic Dexron III fluid as Tremec recommends is my next/best option.

I just made the switch from RP to Dexron III & can say the RP could handle the heat better than Dex III - they both aren't that great but think If I change it more often my satisfaction will increase. I plan on trying redline next.