I am about done with my SMF conversion. I need to pick up some fluid for it tomorrow and was wondering what the majority of you guys are running now. I was running Royal Purple Synchromax, should I stick with that and just overfill it? I did some searching and saw some issues with the 30w in cold weather but wasn't sure how cold it was for those people. It doesn't usually go lower than the high teens out here. I'm also wondering how much I should put in to overfill it, I saw one post that said 6 quarts and was wondering if thats the norm. I'm really looking forward to driving my 93 again, I miss my stacks.

 

The stated capacity is 3.1 quarts, but most overfill it to make it quieter. I filled it from the top, just remove the two top boots and put 4.5 quarts of ATF in. Of course is was out so it was very easy. I read that others installed a pipe elbow in the fill port to be able to put a extra quart in, seems like a good idea to me, just have not needed to do so yet. I read about overfilling and there was one guy who put 7 quarts in his ZF and he had some issues, I'd keep it to 4-maybe 5 quarts.

I just run ATF, I read that would be okay in it, maybe other will chime in on fluids, I have only had my ZF for a couple weeks.

 

Recommended fluid by Ford is Mercron 5.... i run Valvoline Mercron 5 and have had no issues with it i do some heavy towing and alot of highway driving. they said these trans were designed for Auto Fluid not gear oil like the T18/19 same for the transfer case..... Mercron 5

 

I run 4 Qts. mercron- dextron filled threw the shift lever housing with no problems in my 85, and the 97 stroke. The 90 is just filled threw the side fill plug until it runs out.

 

The synchromax I was running is intended to go in manual transmissions that require ATF. I guess I will stick with that then, just add a bit more. The transmission is back in but I have left the shifter off so I could fill it up.

 

i was told the syncromax is actually meant to be used in chevy manual transmissions.... don't know why or what the difference is but ford said Mercron 5..... to each his own.... use what works for you thats all ya can do

 

I hear alot of guys like 10-30. Dunno why.