Overheating transmission

[Gabbzthegoat]

Hi , I just recently purchased a 2014 Ram Rt with the 8 speed and the transmission seems to be over heating , on the street I get temperatures anywhere from 190-210 and on the freeway cruising at 70 they shot up anywhere from 230-250, I’ve noticed that when I have to AC on it stays cooler so that leads me to believe it’s not the transmission cooler. Any ideas on where to start ? Bought truck used with 40,000 miles it at 42,000 miles now

 

[caulk04]

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...

www.ramforum.com

None available at the moment, going on vacation. Soon though, or go for one of the other options if you're impatient and/or real cheap.

 

[kurek]

It's my understanding that the 8HP was designed to run ~190-240F

Despite that it's low mileage, your truck is ~7-8 years old, how is the engine coolant? Since you mentioned you notice lower trans temps with the AC on, that's when the electric radiator fan will be on continuously instead of just in response to engine temperature.

The coolant is a 10 year maximum service interval fluid anyway so it's not a bad idea to start thinking about coolant service. My 2015 only has 41k miles and I recently bought the requisite coolant & distilled water to do coolant service on it, will probably get to that before winter.

One thing that always bothered me on these trucks is the coolant overflow reservoir and the windshield washer reservoir are just little yellow caps on either side of the hood with a graphic embossed on them. Given how easy it is for people to make mistakes, I wouldn't be surprised if there are a number of Rams driving around out there with windshield washer fluid in their radiators

 

[caulk04]

The engineers obviously chose to design the trans to run hot in the 1500 Rams for fuel economy reasons. They're the only ones with fluid heaters. I suspect yours isn't shutting off flow through the heater unit and putting fluid through the cooler. That's really the only way I can see the trans running so much higher than coolant temp. Considering the 'sealed for life' theory of these things, running the fluid so hot is ludicrous. High temps break down oils over time, the higher the faster.

Before I bypassed mine, it would level off around 180 and I never even saw high ambient temps before I (IMO) fixed it. Might have seen 50º outside.

 

[Wild one]

It's my understanding that the 8HP was designed to run ~190-240F

Despite that it's low mileage, your truck is ~7-8 years old, how is the engine coolant? Since you mentioned you notice lower trans temps with the AC on, that's when the electric radiator fan will be on continuously instead of just in response to engine temperature.

The coolant is a 10 year maximum service interval fluid anyway so it's not a bad idea to start thinking about coolant service. My 2015 only has 41k miles and I recently bought the requisite coolant & distilled water to do coolant service on it, will probably get to that before winter.

One thing that always bothered me on these trucks is the coolant overflow reservoir and the windshield washer reservoir are just little yellow caps on either side of the hood with a graphic embossed on them. Given how easy it is for people to make mistakes, I wouldn't be surprised if there are a number of Rams driving around out there with windshield washer fluid in their radiators

How do you explain the 3/4 ton trucks with the 8 speed then,they normally run down the road in the 160F range unloaded and only see upwards of 165-168 pulling 10,000lbs,that's gotta make you wonder about why the 1500's run so much hotter. My wifes 2019 Challenger takes upwards of 60 miles on an 80F day at 70/75 mph before it'll get to 160F