Using the proper fluid for your transmission is very important. All transmissions made after the C4 and C6 should use synthetic fluid - specifically Mercon V. The friction materials used in these transmissions are currently made to be compatible with that fluid. The C4 and C6 should use type F only because it is a limited slip fluid reqired for the friction materials used in them. The only exception is when carbon or Kevlar friction materials are used in a racing transmission - you should then use the fluid recommended by the builder.
Here's some more info on the AODE/4R70W shudder problem. Units older then 98 are more prone to develop the shudder. 98 and newer are less likely but if they do it may occur at higher mileages. The cause is breakdown of the oil by increased mileage and primarily due to heat. The fix is to add an additional oil cooler to keep the temps down. And switching to Mercon V. Here is the article: http://tccoa.com/articles/tranny/transmission/page4.shtml R
Ok, so if my C4 has the heavy duty, or "racing" clutches and the kevlar band, will type F hurt it? I've put about 10k on it, should I change it to something else? My builder is a friend (plus he's a Mopar/GM guy, just happens to be a great tranny builder regardless of make) so he never specified what to put in it other than "whatever Fords take"
most guy's I know that run a C4 built for racing use tractor hydraulic fluid. It comes in 5 gallon pails and is normally used in dozer's, front end loaders, back hoe and other machinery
Most of the "racing clutches" in use are not carbon or Kevlar. If your transmission is used on the street keep type F in it. For the quarter mile there isn't enough heat built up from slippage to worry about which fluid it uses. I have several C4s running type F that are race only without a problem. I also have at least one C4 that is filled with Mercon V running carbon clutches and Kevlar bands that is a race only car running turbo and nitrous. He is using what I recommended and it has not been a problem. I have also had customers who "knew more than I" and ran a different fluid in their street C4s and burned them up. They paid parts and labor to have the transmission rebuilt and used type F without any future problems. I always tell people to run what the builder recommends - that way its not their fault if it burns up. As a builder I always recommend (the warranty demands it) type F for street cars. I never use kevlar or carbon friction materials in street cars. Carbon/glass might be ok but Kevlar is not for street use - it slips at a rate of about 50 rpm according to every study I have seen - wet or dry. That builds a lot of heat on even a short twenty mile trip. Carbon/paper lining is ok for street use but it is not as aggressive initially (dynamic coefficient of friction) as the paper compound alone. Type F really shines best when the friction material is aggressive because it is a limited slip fluid that can take about 50F more heat than Dexron. It will not take as much heat as the synthetic fluids, like Mercon V but they are too slippery to use with paper clutches. They also have to get rid of that heat so you have to use lots of cooler with them.
