While towing I noticed that the trans temp would start to rise and then suddenly reverse direction. I thought that was peculiar and couldn't figure out what was going on. Then last night I was reading the service manual and came up with this. Is anyone familiar with the setting? When does it come on?

Somewhere else in the service manual it states that a malfunction of the thermostat can cause the trans fluid to get hot.

Its inside the cooler at the input. Looks like a spring loaded unit.


TRANSMISSION OIL COOLER THERMOSTAT

NOTE: The transmission oil cooler uses an internal thermostat to control transmission oil flow through the cooler. This thermostat is servicable. 1. Remove the transmission oil cooler (Refer to 07 - Cooling/Transmission/COOLER, Transmission Oil - Removal) . 2. Remove the snap ring (4) retaining the thermostat end plug (3). 3. Remove the end plug (3), thermostat (5) and spring (2) from transmission oil cooler .

 

What Trans Temps are you seeing when you haul? I have been running between 200 and 230 depending on grade, outside temp, etc. I dont see any sudden changes in trans temps (like you would with a thermostat switching on) unless one of the outside factors changes. I just had the dealer switch out the 3.21 gears for 3.92's. I'm hoping this will take some of the stress off the trans and mabe lower the temps.

 

I noticed the "switching" of the ATF temperature in the spring. We drove from southern Cal to Cortez, Colorado and the outside temps were anywhere from the mid 60s to the mid 70s. The ATF temp readings were mostly below 200 degrees. I would be driving up and down grades and was playing with the tow-haul on and off trying to figure out the best speed and gear combo. I would see 185 steady then up to 200 then suddenly, it would go back down.

This past month we took our last trip of the year and drove mostly uphill (up and down inclines) and I was surprised to see temps in the 208 to 215 range for the trip. The outside temps were mid 80s to low 90s. On the last part of the trip up a steep grade, the temp went up to around 227 or so, maybe 235 at the very end when I pulled into the campground.

I tow a 3500 Lb trailer with the 3.21 gears and it doesn't feel like the truck is having any issues. The engine temps are all OK. So now I wonder if the thermostat is not doing it's job.

 

bear, how much did they charge you to do that parts and labor, and what did they say about your warranty? noticed you are in ga also, what dealer did you use?

 

Plumcrazy, Thank you for your service to our Country!

I'm just Northeast of Atlanta and used Mall of GA Dodge/Jeep where I purchased the truck. They quoted $1,860 parts and labor. I had to put $1,000 down for the parts since they had to order them. While I was waiting for the parts order they sent me a 10% off coupon so I ended up at a little over $1,700, all in.

I asked about the warranty several times (I have the '09 with the lifetime warranty) and every time they responded that it would remain in place. They did tell me that if anything ever happened and I needed a repair, make sure to tell the Tech the gears had been changed out. I plan on driving this truck into the ground so we'll see if I ever have to use the warranty.

 

The more I look into it, the more I see how sophisticated the whole transmission shifting and behavior is with these new 4th gen rams. It seems that when Damlier bought Chrysler, they brought in a whole new technology to Dodge. Here are some quotes from the service manual.

I've looked at and smelled the trans fluid since my last ow trip and everything seems normal. I went to a trans shop and talked with the owner about changing out the fluid and he said to wait a little longer. I'm thinking 25-30 K miles I'll do a trans service.

What I've never been aware of though, is that there is a thermostat that controls the ATF flow through the cooler. I would think that free flow would be the way to go. Since Chrysler went thought the expense to design in a thermostat into the ATF coller is just way out there for me.

OPERATION
The transmission temperature sensor is used by the TCM to sense the temperature of the fluid in the sump. Since fluid temperature can affect transmission shift quality and convertor lock up, the TCM requires this information to determine which shift schedule to operate in.

Calculated Temperature
A failure in the temperature sensor or circuit will result in calculated temperature being substituted for actual temperature. Calculated temperature is a predicted fluid temperature which is calculated from a combination of inputs:

• Battery (ambient) temperature
• Engine coolant temperature
• In-gear run time since start-up