What ATF to Use?

[LiLMike 42]

I have a brand new 4R70W that I am putting into my 69 Mach1. What ATF should I use and how much. This includes the torque converter also. I have read that Mercon V is recommended but the transmission shop mentioned Mercon 6. Also what are your thoughts about synthetic?

[Caseyrhe 650]

I would ask the shop who rebuilt it or call manufacture. On my 68, C4, he said to use the mercon due to the clutches he put in. On my Mach, C6 he said Synthetic due to the clutches. C4 was 5 quarts, start in neutral, add as needed, took total of 9? He also told me to go from neutral to reverse to wash/blow out any possible residual thrash into pan.

[Rsmach1 71]

Mercon V, and about 12qts total with the converter. Ford had a TSB recommending this fluid to help with a torque converter shudder issue.

[LiLMike 42]

Good to know guys. The shop I mentioned was the one that built it. That is why I was confused. He said Mercon VI but I read on the Ford Parts site to use Motorcraft Mercon V. I going to assume that Ford knows what they are talking about. I do have the Red Eagle clutches in my tranny.

[Rsmach1 71]

You can use mercon VI as well, I believe Motorcrafts V is a semi synthetic and VI is a full synthetic.

If your tranny guy says mercon VI, by all means use it. The TSB I referred to was probably prior to mercon VI being available.

[MikeStang 247]

I run Mobil 1 full synthetic in my 4r70w

Going to full synthetic made it much smoother.

You can slip it into gear and can't even feel it haha.

I would use Merc V or VI or Mobil synthetic...all are rated for that trans

[LiLMike 42]

It's funny, on the Ford Parts website there is no Mercon VI listed. Just Merc V I may go with full synthetic Mobile 1. So with the torque converter I would need about 12 quarts?

[Rsmach1 71]

Roughly, buy 13 or 14 to be safe.

[LiLMike 42]

Thanks guys! As always This site and all ya'lls knowledge comes through again.