66RFE Drain Back Problem

[Bob Johnson]

I have a 2016 RAM with 6.4 Hemi, 66RFE and 67K miles on the truck. I changed the transmission fluid at 60K with Amsoil full synthetic.

When I first start the truck and place it into drive, if I don't wait 15-20 seconds, it is like the truck is in neutral. Pressing on the gas it revs but goes no where. If I wait 30 seconds and press on the gas, it moves fine. I have this problem when the truck sits for more than 36 to 48 hours without being started. Once the trucks starts moving there are no more issues until it sits another 36-48 hours without being started.

I've been told that this is called "drain back", when the fluid drains back out of the torque converter. I've also been told it could be a faulty spin on filter in the tranny or a bad thermal bypass valve causing the drain back to happen.

Has anyone else had this problem? If so what did you do to fix it?

 

[tron67j]

Did you check that the filter is OEM or equivalent, I have read that there is a anti-drain back valve built into the filter. Also, can't speak to transmission fluid but Ram is fickle with other fluids being OEM, maybe the fluid you used is an issue(?).

 

[HEMIMANN]

Likely filter related if the oil isn't be circulated immediately.

I always change both filters to ensure lowest flow restriction in this marginal transmission. Yes, I have the 66RFE. No issues up to 60k miles. I changed oil and filters twice, now with Red Line C+ATF, Mopar sump filter, Wix synthetic control filter. Transmission has never shifted this good when it was new.

Also - did you put a thermostat bypass on the oil cooler line? Important to reduce oil deposit formation.

 

[Bob Johnson]

Did you check that the filter is OEM or equivalent, I have read that there is a anti-drain back valve built into the filter. Also, can't speak to transmission fluid but Ram is fickle with other fluids being OEM, maybe the fluid you used is an issue(?).

The filter is not OEM because my dealership gave me the wrong filter. I didn't know this until I had dropped the pan and drained the fluid. They didn't have the correct one in stock so I was stuck using one from Advance because I couldn't go 3 or 4 days without my truck.

I have heard there was a drain back valve in the filter too. However no one has confirmed for sure. I'd like to know before I drop the pan again and replace it with an OEM and find out I still have the same problem.

 

[Bob Johnson]

Likely filter related if the oil isn't be circulated immediately.

I always change both filters to ensure lowest flow restriction in this marginal transmission. Yes, I have the 66RFE. No issues up to 60k miles. I changed oil and filters twice, now with Red Line C+ATF, Mopar sump filter, Wix synthetic control filter. Transmission has never shifted this good when it was new.

Also - did you put a thermostat bypass on the oil cooler line? Important to reduce oil deposit formation.

Yes I changed both filters however they are not OEM (see reply to tron67j). The transmission does shift awesome and works fine. It's just this annoying issue when it sits for a day or two.

I have not replaced the thermostat bypass yet. I wasn't aware of this issue until a few days ago. I have ordered a new bypass valve from ATS. I don't think mine has gone bad yet. I monitor the trans temp when I'm towing. I have never seen it above 178 degrees even in the dead of summer heat. Most of the time it stays around 160 to 172 degrees.