2016 1500 8 speed 5.7 Hemi Overheating Transmission Issue

[tjmaak]

I have a 2016 1500 w/ 5.7 and 8 speed transmission. Starts to overheat driving down the interstate around 75-80 mph or hauling a camper (6500lbs) but it doesn't seem to happen untill Im about 45 minutes into the drive. I let it get to 240 degrees before I pull over and let it cool. I recently had a local transmission guy look at it and he couldn't get the truck to replicate the overheating issue. He checked the cooler lines and said they were clear and performed a routine service to it and found no issues. Does anyone think that this is more of an internal issue of the transmission or have any ideas of what to look for next? Would an extra cooler do the trick? Truck has 95000 miles.

 

[hunterdan]

It's possible that the thermostat on the side of transmission is sticking and not allowing the fluid to cycle through the cooler.

 

[tjmaak]

Thermostat was good

 

[crash68]

If the 8HP70 temperature is spiking, there is most likely an issue with the thermal bypass valve in the TMU on the side of the transmission. An extra cooler isn't needed, either replace the TMU or there's a bypass available for the TMU.

 

[tjmaak]

Do you have a link to the part? I can't seem to find one. Do they have it on rockauto?

 

[Burla]

Nothing is surprising with those circumstance and temps with that transmission, good on you for pulling over, now do all of the deletes you can, look them up. Thermal bypass, shutter delete, and I might think there is something else, pm wildone. Whatever, just delete all of the garbage the gov't made your manu put on your truck. The us govt decided that if you run transmissions hot it is great for fuel mileage which is also a load of rymes with erd. I have the info for the rfe, just not the 8 speed, but there are deletes for the 8.

 

[Wild one]

Thermostat was good

How did he check the transmissions thermostat in the thermal management unit?? That thermostat is just a light duty pellet thermostat,kind of similiar to the engines thermostat,and has been known to have issues with sticking as HunterDan stated.
Read through this thread,as Caulk04 has developed a thermostat bypass for the 8 speeds.

8hp70 heater bypass

Starting this thread to consolidate some information that we've been discussing (https://www.ramforum.com/threads/revmax-8-speed-thermostat-bypass.171776/unread) on the topic of keeping the 8hp70 cooler than stock. Here you'll see the thermostat assembly broken down into its individual...

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