Street TH400, 430hp, 520 lbft. What ATF to use?

Street car, has a fully rebuilt TH400 and I will be running one of Jim's TSP converters.

Trans mechanic said I can use whatever fluid floats my boat.

I understand Dex 6 is much thinner viscosity than Dex 3 however Dex 6 has a longer service life.

This is going to be driven maybe 3000-5000 miles a year and is primarily a street car.

So, what would you guys pour into your fresh trans, III or VI ?

PS, does brand matter? I know I can spend $12 a quart on fancy synthetic, but I want something that is common and simple for the poor fool (my son) who will own this car after I'm dead.

 

I would use either plan dex/merc of old fashioned type f. Just be clear to you son what fluid is in there. I don't see the need to pay crazy fluid price for this

 

Type F.
Patrick

 

I have always been told type F was for Fords. Why is a Ford fluid a better choice than the Dexron?

 

Less clutch slip resulting in firmer shift.

 

I also use the Valvoline max life synthetic. It’s on sale right now at AutoZone for 23 bucks a gallon. Hard to beat that price for a synthetic fluid.

 

I was told a long time ago to use Type F by TCI?? I do know type F has a higher viscosity than Dexron resulting in a higher line presure, which results in less slip and firmer shifts like said above.
With that said, Larry mentioned Max Life fully synyhetic. That covers almost all trans fluid specs...