Mixing RP Max ATF with DEXRON VI

[Neil_A]

Vehicle info is in sig with a 4T65E transmission.

I am dropping my pan Monday, replacing my filter, and switching to RP Max ATF. My previous drop and fill was with Castrol DEXRON VI. Since a pan drop doesn't come close to getting all the fluid out will I be okay mixing the two? I have had great success with RP's oil, thus the reason for the switch.

 

[blue94]

yes, it will be okay.

 

[unDummy]

Why the brand change?

Mixing is fine. Post back on the results.

 

[Neil_A]

Results:

So far so good. My pan and internals were immaculate and the fluid coming out was cherry as my mechanic put it. I stood by him through the entire job. Took 7+ quarts of RP. Shifts are noticeably smoother yet still crisp and firm when you stomp on it. My temps appear to have gone down, and my fuel economy seems to have gone up. I wont know for sure for at least a couple more fill ups though. So far I am very pleased.

 

[Oldwolf]

I wonder why would the ATF temperature have gone down with RP?

 

[unDummy]

Its thicker. Maybe less TC slippage, more holding capability, different line pressure curve........

DexronVI overhyped by GM anyway!

 

[akela]

In the same 4T65E transmission, I had problems with Dexron-VI. In the hot weather, after some stop-and-go city driving, the system was going to the "max adapt" mode (raising the fluid pressure as a response to slow shifts), and shifts became really hard.

I think it's viscosity difference to blame.
Dex-III is 8 cSt, Dex-VI is 6 cSt (at 100C), which is huge difference.

 

[mcrn]

Originally Posted By: unDummy
Its thicker. Maybe less TC slippage, more holding capability, different line pressure curve........

DexronVI overhyped by GM anyway!



Would you please tell us how its overhyped? Im curious because I am using it and have been wondering about trying something different.

 

[unDummy]

100k change intervals by GM, and everyone claiming how great it is. Has been mentioned in these forums regularly since its release. I've flushed out too many with under 30k with improvements to shift quality and transmission feel. Its not a 100k fluid as some insist it to be. They should've just called it DexronIIIi ... but, what would the marketing department do?