Are preium synthetic ATF's too good?

[JPul]

I want to change the ATF in my truck as I have purchased a Mag-Hytek pan and want to make use of it and it seems appropriate to me to change at the same time.



I went into a local performance shop and asked for a recommendation for a premium ATF fluid for a 48RE behind a Cummins. The response was effectively not to do it because the premium ATF's such as RP ATF+4 or Redline CATF+4 are too good, too slippery and are allowing slippage which is the heat generating killer of auto trans. They would love to sell me the premium stuff but recommended standard ATF+4 at very regular change intervals because of their experience with the 48RE mated to a Cummins and the use of the premiums.



My thoughts would be that any ATF provided to meet the requirements of ATF+4 would have the appropriate friction modifiers to satisfy this specification. I would like to use the premiums to get the max high temp capabilities for my trans in my towing application.



I would appreciate your thoughts.



Regards, John

 

[firemansdiesel]

Diesel shops are like CTD forums. 100 different responses to a question (who's right?). Ask another shop and they will tell you a different choice. It's all preference, I think the guy behind the counter is full of BS. Buy what makes you happy as long as it meets the specs.



I have Amsoil in my transmission/transfer case. Never a problem w/ temps nor performance. Go w/ Redline, RP, Amsoil etc... .

 

[cerberusiam]

Well, ATF+4 is a synthetic also and rated to 320 degrees. The question is do you need more protection? If so then as long as the other fluids meet the ATF+4 spec they should be fine.



BTW, most of the additives make the fluid stickier at higher temps and preserve the seals better. The guy is blowing smoke about something he heard and does not understand.

 

[WCounts]

I don't know about a stock transmission but for a built transmission I believe most folks are using Dextron III. I believe it's better to use enexpensive fluid and change it often. I change mine every year.