Summit. Arrives at your door in a couple days. You only need 3 quarts, so I wouldn't sweat it if the dealer is a couple dollars more.

Tremec puts a piece of paper in the box that says:

"We recommend GM synchromesh part # 12345349, or Dexron III / Mercon Spec ATF fluid for all TKO
transmissions."

It doesn't say Pennzoil, RedLine, Royal Purple, or anything else (all great products BTW). So it is GM Synchromesh for me. I'll spend the extra $10 on my brand new $2300 transmission. It does seem like everyone goes for Synchromesh. I haven't heard anyone that has been using Dextron III.


FYI - That part number has changed. It is now labelled as AC Delco and is part #88900333.