My trans has a manual valve body in it. Would the extra friction modifiers really matter, since I am manually shifting it? Is there a concern with clutches slipping because of the extra modifiers?
The transmission still applies clutches and bands the same way whether it shifts manually or automatically.
If you're not experiencing slipping now then as long as you haven't done a huge increase in torque you'll probably be fine, but why risk it? I don't think any of the big power diesel trans builders are using, or recommending +4 , I know my mentor was totally against it back in 2001 when I was working for him. My 2000 Cummins Ram only had + fluid in it for the first 30k miles , after that I never used it .
