Type F or Mobil 1 ATF or ?

[nmgearguy]

Had a shop in Albuquerque, NM build up a C4 for me and guy says, “just use a good synthetic ATF and your good to go”. So I buy a case of Mobil 1 and a few thousand miles down the road I start looking closer at what other folks with C4s are using and it’s all over the map. And to top it all off, everyone I talk to has a different opinion, including the transmission shops. So here’s the poll: What ATF are you using in your C4?

 

[badmuttstang]

I have two favorites Royal purple for my newer cars and trucks but for C4 or C6 I like B&M trick-shift seems to give a firmer shift and run cooler but as you stated everyone has a different opinion or preference

 

[DirtDonk]

You might ask the builder why he recommended something other than the original specified fluid. They might have used a different clutch material that responds well to synthetic. And since synthetics tend to lubricate and cool very well, perhaps he's thinking about that too.
Is he going to stand behind his product? If so, I'd use what he said.

Paul

 

[badmuttstang]

Good point DirtDonk I had a AODE built that the builder said to use Type F not the dexron/mercron so ask him why he said to use it.

 

[broncnaz]

Basically on a rebuilt tranny you can use whatever but you usually need to stick with what ever you first used. Different fluids have different friction modifiers in them and can causes issues when mixed.
There's even guys using hydraulic fluid for tractors in there tranny's. As some of the fluids supposedly have better additives and is cheaper than automotive fluids.

 

[sgtdcoulter]

On the older units that came w/ Type F then I would stay w/ Type F. If it has been completely OH'd then a good brand name syn is ok also, if you wish to spend that type of $. As the others say, if he recommends it then, have it in writting on original invoice and that will tell you if he will back it up. Different type fluids definitely react against each other. Some tractor hydraulic fluids will work also. Read the fine print on the labels,Older non electronic Allison Transmissions even allow top grade 15w40 oil for running in the units. It should read c-4(Not to be confused w/ c4 transmissions) compatible on the labels of the oil.
It is like coolant and can be very confusing at times.

 

[nmgearguy]

Thanks for the comments and advise. I'll definitely call the transmission builder back and try to understand his logic. At this point, to error on the safe side, I ordered a case of synthetic type F. Really interesting that this is such a poorly understood issue.

 

[NYLES]

i have two favorites royal purple for my newer cars and trucks but for c4 or c6 i like b&m trick-shift seems to give a firmer shift and run cooler but as you stated everyone has a different opinion or preference

x2 great stuff!

 

[broncnaz]

While it probably is poorly understood on the otherhand theres not much to understand. Kinda like motor its not recommended that you mix brands or weights either. Its just that people dont pay attention to what they are pouring in sometimes and it causes issues. Most dipsticks are marked with what the tranny requires. If 2 oils react to one another then you"ll have major issues. As was mentioned certain clutches and bands need a certain additives to help either with slippage or lock up. Certain oils not having have such additives and may accelerate wear or just cause major slippage.