transmission temperature running hot

Hairy Fufton · May 28, 2017

I was hoping someone might have seen something similar and have an idea how to proceed.

We take our 2 wheel drive, 2015 5.7 hemi, 8 speed, big horn on a couple of trips a month. On the last 2 trips, the transmission temps jump from the normal range (188 to 192) to 235 to 240. Thats running at 80 mph, not towing or with a payload, on level ground.

But, it happens like this. Driving at 80mph for 30 to 45 minutes, the coolant is 195 - 200, oil temp is 210 - 215 and the transmission is at 188 - 192. The coolant temperature spikes to 225 for about 3 - 5 minutes, then drops back to 200 and the transmission temps spikes 235 to 240. Slowing down doesn't help. The 6 and 7th gear then whines slightly when it down shifts but 8th is fine.

When we stop for she break, it starts over.. normal temps, then a spike in transmission temperature.

Any ideas would be helpful..

tsielski · May 29, 2017

Hard to diagnose remotely, but the 8-speeds have a heat exchanger box attached to the drivers side which uses engine coolant to warm/heat the transmission fluid. This serves to warm the transmission faster, and unfortunately to keep it warmer than it otherwise would be. Also built into this box is a thermostatically controlled valve that doesn't allow the transmission fluid to flow thru the transmission fluid cooler (which is incorporated in the radiator) until the fluid reaches 180 degrees. This also keeps the trans fluid at least 20 degrees warmer than if the fluid flowed thru the trans cooler at all times.
It could be that this thermostat valve is malfunctioning, not letting the fluid flow thru the cooler consistently.
It also could be some serious clutch slippage issue internal to the transmission, but in either case a competent repair facility will need to diagnose.
Good luck.

tsielski · May 29, 2017

Another thing. Your coolant temps spiking like you reported doesn't seem normal either. Hot coolant temps will tend to raise the trans temps because of that heat exchanger attached to the transmission.
Before I installed a 180 degree thermostat, and removed all but two of the shutters, I seem to recall coolant temps being in the 206 to 210 range while cruising @ 75, and trans temps tended to stay in the 186 to 190 range. That was in the fall with ambient temps in the 50's to 60's. The OEM engine thermostat is 203 degrees.
What were the ambient temperatures when you experienced these fluctuations?
Your engine thermostat could also be having issues, however those tend to fail in the open position and your engine would run too cool.
The way my truck is presently configured (180 thermostat, and all but 2 of the shutters removed), my coolant temps stay in the 185 - 188 range. Even in ambient conditions of close to 90, while cruising between 75 and 80, coolant temps seldom climb higher than 190.

First thing I would do, were this my truck is replace the thermostat. It's an easy job, and the units are inexpensive. I would also replace the coolant you drain prior to replacing the thermostat with a new 50 - 50 mix, and not re-add the drained fluid. The OEM stuff is a bit pricey (~$25 gallon), but you won't have any chemical compatibility issues.

If the situation persists afterwards, I would seek professional assistance.

Burla · May 29, 2017

Tell the dealer.

StoneDude76 · May 29, 2017

Maybe the coolant bypass valve. Mine was stuck open and my trans wouldn't break 140 normal driving. Dealer replaced and now it reaches 170 in normal driving conditions.

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VB712 · May 29, 2017

tsielski said:
Another thing. Your coolant temps spiking like you reported doesn't seem normal either. Hot coolant temps will tend to raise the trans temps because of that heat exchanger attached to the transmission.
Before I installed a 180 degree thermostat, and removed all but two of the shutters, I seem to recall coolant temps being in the 206 to 210 range while cruising @ 75, and trans temps tended to stay in the 186 to 190 range. That was in the fall with ambient temps in the 50's to 60's. The OEM engine thermostat is 203 degrees.
What were the ambient temperatures when you experienced these fluctuations?
Your engine thermostat could also be having issues, however those tend to fail in the open position and your engine would run too cool.
The way my truck is presently configured (180 thermostat, and all but 2 of the shutters removed), my coolant temps stay in the 185 - 188 range. Even in ambient conditions of close to 90, while cruising between 75 and 80, coolant temps seldom climb higher than 190.

First thing I would do, were this my truck is replace the thermostat. It's an easy job, and the units are inexpensive. I would also replace the coolant you drain prior to replacing the thermostat with a new 50 - 50 mix, and not re-add the drained fluid. The OEM stuff is a bit pricey (~$25 gallon), but you won't have any chemical compatibility issues.

If the situation persists afterwards, I would seek professional assistance.

How did you remove the shutters? Any issues or check engine lights from it?

tsielski · May 29, 2017

Didn't remove all of the shutters. The top most and bottom most ones are still present. Doing that is easy. After removing the grille, the shutter assembly is easily removed from the radiator support bracket by removing a few bolts and the electrical connector. The middle shutter blades just pop off the vertical plastic support rods which are connected to the rotator arm of the electric motor.
Leaving the upper most and lower most ones in place still produce enough resistance so as not to throw a code. I've read on this forum that if you remove all the shutters, and reinstall the completely empty shutter assembly, and reconnect the electrical connector, you will generate a code.
There also is another thread on this forum, where a member posted a short video how to completely remove the motor from the shutter assembly, make a modification to the motor that rotates the shutters, so the completely disconnected motor still rotates in it's arc, and no code will be generated. The motor, re-connected to it's electrical plug, is attached in an out of the way place on the radiator support bracket, and the entire shutter assembly, less it's motor is discarded. I chose not to go that route, and just remove all but the upper and lower blades.

Hairy Fufton · May 29, 2017

I haven't removed any shutters and it hasn't thrown any codes. The transmission overheat is 275 but I think that is too high.

I think it might be a valve failure as well.

RamCares · May 30, 2017

Hairy Fufton said:
I was hoping someone might have seen something similar and have an idea how to proceed.

We take our 2 wheel drive, 2015 5.7 hemi, 8 speed, big horn on a couple of trips a month. On the last 2 trips, the transmission temps jump from the normal range (188 to 192) to 235 to 240. Thats running at 80 mph, not towing or with a payload, on level ground.

But, it happens like this. Driving at 80mph for 30 to 45 minutes, the coolant is 195 - 200, oil temp is 210 - 215 and the transmission is at 188 - 192. The coolant temperature spikes to 225 for about 3 - 5 minutes, then drops back to 200 and the transmission temps spikes 235 to 240. Slowing down doesn't help. The 6 and 7th gear then whines slightly when it down shifts but 8th is fine.

When we stop for she break, it starts over.. normal temps, then a spike in transmission temperature.

Any ideas would be helpful..

Hi Hairy,

Are you still within your factory warranties? If you're considering working with your Ram dealership for diagnosis, keep us posted!

Kori
Ram Social Care Specialist

Hairy Fufton · Jun 28, 2017

OK. an update on the issue.

I have removed the shutters (left the top and bottom ones and its very easy to do).

We had a trip, around 800 miles total. It appears that driving for around 30 minutes at highway speeds, the transmission temps will slowly climb to 240 and hold steady. If we stop for a few minutes, the transmission temps will drop to 188 and start over. Driving around town, the temps are 203 coolant, 188 transmission, and 213 oil. Removing the shutters has caused the coolant temps to remain more stable.

However, on this trip two new things happened.

1. I went to pass a slower truck running at 50 mph on a 2 lane highway and when i gassed it up, the transmission couldn't select a gear and then SLAMMED hard into a gear when i backed out of the gas. hard enough to think i had hit something in the road. This happened 2 times and the transmission temp was in the 235+ range. I babied the truck for the remainder of the trip.

2. on the way home my fuel mileage was 16.4 mpg for 420 miles. running on level ground, 2 suit cases in the bed and no wind and not towing anything. I normally get around 24 mpg on a similar trip.

Now that we are home and driving around town, the temps are all normal and i cant get the transmission to replicate the shifting problem.

GsRAM · Jun 29, 2017

At this point, I'd agree with the other suggestions, time to take it back to the dealer, throughly explain all you have done and see what they can come up with. Good luck

transmission temperature running hot

Hairy Fufton

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tsielski

Senior Member

tsielski

Senior Member

Burla

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StoneDude76

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VB712

Maxi_built

tsielski

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Hairy Fufton

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RamCares

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Hairy Fufton

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GsRAM

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