# Proper transmission warm up on a cummins/aisin



## cmo18 (Mar 10, 2008)

On my 2006 cummins i was always told to use high idle and place transmission in Neutral. Tranny gauge shows it warming up...

Now on our 07.5 6.7l cab an chassis that has an Aisin tranny, high idle only works in Park. A tranny guy said this tranny allows the fluid to move in park, any truth? 

What do you guys do? Not much info on aisin tranny


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## OneBadDodge06 (Sep 22, 2004)

Unless things have changed or the several people I've had tell me this are just screwing with me that fluid only pumps when its out of park. These are mechanics so I tend to believe them...said they've seen several dodge trucks with burned up trannies bc the owner let it idle in park.

I think there's some truth to this bc when it starts getting warm, I'll put it in neutral and set the parking brake to take a break, come back and its dropped 15*.


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## Dogplow Dodge (Jan 23, 2012)

Its true for my year. I disconnected my trans cooler line to flush the system, and it can sit all day disconnected in park with no fluid loss. Soon as i put in neutral, it pumps out like a garden hose gone crazy. Every morning i start it up to warm the truck, it gets put in neutral to do so

I have the 518 with electric OD. Fluid level can only be checked in Neutural, as if it's in park,it won't give a proper reading.


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## cmo18 (Mar 10, 2008)

On the 2006, yes I agree the neutral to warm it up...I've done it since new.

What about the aisin? I found a technical info PDF online that shows line pressure is the same for neutral and park, but I just want to make sure. And someone told me the aisin flows even in park.

http://www.trucktransdiag.com/downloads/aisin-as68rc-Tech-Info.pdf


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## SnoFarmer (Oct 15, 2004)

"only flows in park"
This is NOT true for the 68RFE. It was true for the old RE-series transmissions (47RE, 48RE) behind the 5.9L, but not for 6.7L / 68RFE. The 68RFE (and its cousin the 545RFE for gas applications) 
Park and Neutral are hydraulically identical, so the pump will circulate oil in ALL gear positions (including Park and Neutral). thus
the 68RFE has cooler flow, etc. in Park . So the cooler flow should be identical (and sufficient) in either position.





Most likely reason your temp is running higher in Park is simply that you have no airflow through the cooler, so you're adding a continuous small amount of heat inside the trans I would expect you to see the same temp if you idle in Neutral.

Yes. it does flow in "N"

It also will lock you out of 5th & 6th (auto) until it warms up.
and to aid in warm up turn on the EB.


ps auto hi idle will happen all on it's own.
What some are calling manual high idle is actually the PTO control.
Some are using the PTO control as a set throttle and calling it high idle.
To use the cruise control functions to "idel up" have the pto enabled if it isn't already.


pss on the g56 you will need to ground a wire from under the dash also.


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## cmo18 (Mar 10, 2008)

Is that also true about the AS68rc?



SnoFarmer;1748267 said:


> "only flows in park"
> This is NOT true for the 68RFE. It was true for the old RE-series transmissions (47RE, 48RE) behind the 5.9L, but not for 6.7L / 68RFE. The 68RFE (and its cousin the 545RFE for gas applications)
> Park and Neutral are hydraulically identical, so the pump will circulate oil in ALL gear positions (including Park and Neutral). thus
> the 68RFE has cooler flow, etc. in Park . So the cooler flow should be identical (and sufficient) in either position.
> ...


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## SnoFarmer (Oct 15, 2004)

the AISIN-SEIKI trans or for the Dodge is AS68RC. In the NPR trucks its a A465, 
Yes, it does pump fluid in both Park & neutral.


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