I still have the stock trans pan and want to add the 4x4 pan, I don't want to drain the converter, can I add the 7-8 quarts of mobil 1 atf to the the regular stuff? mobil 1 says its compatable with all atf fluids

 

If it says it's compatible, then it should be fine. You're not going to get the true benefit of a synthetic tranny fluid if you mix it half and half though. If you're going to spend the money for expensive fluid, then do it the right way and change the fluid out completely.

 

ATFs with same specifications mix fine.

 

Curious, what is the overall gain of using synthetic, I just put a new 4x4 pan along with the FTVB but used regular ATF..decron mecron III

 

I copy and pasted this from the archives


Factory_Tech
Senior Member &
Supporting Vendor

Registered: Mar 2000
Location: Cincinnati, OH
Posts: 1655
I posted about this somewhere, but the botom line is it has to have the SAE spec on the bottle, and if you look real close, none of the dual usage fluids do, they just say compatible with MERCON, even though the fine print will list a spec number that isn't. The only two things I would put in one are Motorcraft MERCON, or Mobil 1 Synthetic, but any name brand is prolly fine, fluid is pretty much a commodity, as long as the additives are compatible, but Highly Friction Modified fluid (Mercon V and such) are not, the HFM chemicals break down the soft parts over time. That's the reason Ford did not switch the 4R100 to HFM fluid in the first place, a good argument can be made that it's better fluid, it stops converter shudder most of the time, but it don't work in a 4R100. I can't think of any of the designer fluids (Royal Purple, REdline etc...) that are remotely worth the money, excpet to say that a synthetic fluid will hold up in high temps better as a general rule. I use Mobil 1 because it's provided to me for nothing, I wouldn't pay for it living here, maybe if I was in AZ or FL or someplace hot.

G