I have a 05 3500. The tranny seems to do fine just driving around, but every time I pull my camper, about 9500 lbs, the tow haul light comes on and stays on and the tranny gets too hot. The torque converter seems to lock up too early also. The last time i pulled my camper, when the tow haul light came on, my overhead outside air temperature jumped from 81 degrees to 110 degrees. I pulled over and put it in neutral, and when my tranny cooled down, the outside temp dropped back down to 81. Has anyone else had this problem? If so, please help. Thanks

 

You may want to have trans cooler checked read following for procedure to flush cooler and check for restriction. There are two trans coolers on your truck. One is located on left side engine just above the starter motor. The other is located between the intercooler and the engine coolant radiator.
Check engine cooling fan for proper operation also. The outside air temp sensor is located near the external trans cooler and could be sensing the heat from that external cooler.

Trans cooler system flow check procedure.;Applies to most models with equipped with automatic transmission. Tool and procedure available to check auto trans cooler system flow rate.
System or Component Transmission Cooler Flush Tool ( 6906 );Automatic Transmission / Transaxle;Yes - Intermittent,Yes - Continuously
Recommendation Trans should be fully warmed up before flow check is performed. "HOT TRANS" on DRB display indicates trans is warmed up (80 to 240 degrees). Check trans cooler system flow with special tool 6906A (trans cooler system flush machine) COOLER FLOW TEST RESULTS: System WITH auxiliary cooler: Pressure indicated on the gauge should stabilize below (20) psi. System WITHOUT auxiliary cooler: Pressure indicated on the gauge should stabilize below (30) psi. Higher pressure indicates cooler system is restricted. NOTE: For models with 45RFE / 545RFE auto trans see applicable service manual section (21) / Oil Pump section / Oil Pump Volume Check procedure directions. COOLER SYSTEM IS RESTRICTED: See list of possible causes provided below: [1]: Main cooler in radiator is clogged with debris. [2]: Auxiliary cooler is clogged with debris. [3]: Anti-drainback check valve used on some RWD models may be clogged with debris and may stick in the closed position. [4]: Cooler system tubing is blocked / kinked / pinched. [5]: Cooler fittings in trans case are clogged with debris. [6]: Trans filter element is clogged with debris. IMPORTANT: Lack of cooler system flow can cause damage to the torque converter. If trans fluid is burnt and/or the torque converter housing is blue in color from excessive heat replace the torque converter and the converter hub seal in the trans pump. Also replace trans fluid and filter.

 

The one on the left side of the engine above the starter is actually a torque converter cooler. The heat exchanger is fluid to fluid. Mine leaked internally and contaminated the transmission with anti freeze. I've been told a rise in the water temperature gauge can be an indication of the torque converter getting over heated. Doesn't sound like this is your problem but I just wanted to throw it out there.

 

Thanks for the replies! I'll check the cooler tomorrow. I'm still puzzled on how the outside thermometer is being affected. The sensor is in the drivers side headlight and "shouldn't" be picking up on heat from the tranny. Any ideas?

 

It isn't "in" the headlight, it's next to the headlight...and all the heat exchangers.

 

Are you saying you are not turning Tow-Haul on while towing ~9,500lbs but after some point in towing the system turns it on for you, then things start over-heating?

On the '05 trucks the Tow-Haul mode can be programmed in two ways:

1st (and default) is a change in shift-points- Meaning holding gears longer under load/acceleration, quicker full torque converter lock-up between shifts (accurately the only time it will fully lock the torque converter in 2nd gear), and locking/holding a gear for deceleration (w/no throttle applied).

2nd Option is what the older pre-'05's had.... Overdrive/4th gear lock out.


I'm not a fan of the 2nd option, so if that's how your truck is programmed then I can understand why your not using Tow-Haul... You can have the dealer re-program your Tow-Haul mode back to option 1 if it's more your liking. I really only see Option 2 benefiting really heavy seasonal towers like farmers who have the need to tow heavy loads, normally short distances, at slower speeds (55mph and/or lower).

If your truck has the default Tow-Haul programming (option 1), then I don't understand why you wouldn't be using it intentionally. Everything that's in the default Tow-Haul programming is designed to reduce heat while towing.

A 9,500lbs camper is nothing to dismiss in the weight department. It may not be the heaviest, but campers that size are normally 12-13ft high and 35ft long bricks... That's a lot of air your moving. Tell us more about the camper, the speed you cruse while towing, and the terrain you go through.


Oh, I had to replace one of my hard cooler lines a year ago. My trans shop found it kinked... It was the one supplying cooled fluid to the pan. But still my transmission never overheated with the kinked line... Of course our driving styles and terrain might be different.

 

jb,
i have a 2500, 2005 dodge diesel with auto trans.

when i tow my trailer i always engage the tow/haul mode.

it seems to me that trans shifts hard or more crisp in tow haul, someone told me tow haul also increases the shift pressures so there is less change for trans slip.

I do not know for sure, but my truck sure does run great and pulls my trailer fine.

I had the trans drained and filter changed at 42K, when i got the truck used. tech said the old fluid was clean,

i also had the coolant flushed and a new thermostat installed .

so far, mine has been a great truck.

 

You mentioned the engine temp. Mine heats up to a little over half, say 205, then the thermostat opens and it drops to 185 or so, but if I punch it it will jump has up to the 205 range, is this normal?

 

You can take just about everything you read on the overhead console and throw it out the window.. Temps, MPG, heck even my trip meter runs different than my trip on the dash.. The 04.5 and up 48re is notorious for shifting into OD around 45-50 mph. Nothing worse than having a 10,000 camper on the back and shifting into OD at 45mph. There is a dealer flash that you can get that turns the T/H into a OD lock out. Might want to take a look into that as an option.

Its actually just in front of the intake side of the cooler and could be picking up the extra heat coming off the radiator. Again, mine reads +/- 10 degree of what the actual temp is outside. Its even worse on hot days

Completely normal. At around 215 the "747 jet fan" kicks into full drive. Anything under that is within normal temps.

 

Sorry its been awhile since last post. I bought a new cooler and when checking flow of the new cooler compared to the old one, the flow seemed to be the same on both. My thought is that the old cooler is fine. My next step is to remove the check ball in the line. Any helpful tips would be appreciated. Also i understand what you're saying about overhead console readings, mine aint right either. But if the thermometer was picking up heat from the lines wouldn't there be a gradual increase? Why the sudden 30 degree jump?