I intermittently get a code P0740 code in my '09 Ram 1500 5.7L with 3.55 rear axle, but only when towing. When I reset the code and drive around normally without a load, highway and city, the code doesn't return, but after I tow for over 100 miles or so, the code returns. It only occurs while towing, and even occurs when I'm in Tow/Haul mode. Transmission temps are normal when this occurs.

I know that the code is for TCC Solenoid Circuit Open, and indicates that the engine RPM does match transmission RPM, so the converter is not locking up. Because it happens only when the truck is pulling a load, it's probably a mechanical issue. But what? Is my torque converter going bad? Is there a problem with the valve?

I always like to start with the simple stuff, so I'm going to change my transmission fluid. The last time it was changed was 10,000 miles ago (at 30,000 miles), but it was the previous owner so I don't know if it was the proper fluid or not. But if that doesn't solve it, is it time for a new torque converter, valve body, or both? Previous owner did a lot of towing with the truck, as do I.

Thanks for your help!

 

I had a similar issue with mine in 2011, except my code was P0742. It turned out to be a bad TC. Got it changed under warranty and all was good. I wouldn't waste money on transmission fluid especially if you just changed it.

Here was the thread i had back then.
https://dodgeforum.com/forum/4th-gen...-stuck-on.html

 

I've had the same issue. Only when towing my snowmobile trailer, not my boat. It's weird. Just took it in again to have it looked at and they did a TSB on it. It shifts different now and the Fuel saver light comes on when I just let up off the gas....i think it's a band aid. I've done the transmission already in between codes too. I was told last time they'd rplace the TC, but they did this instead. I have lifetime powertrain, but Running it back and forth is a pain. I'm hauling the trailer again this weekend, so I plan on it doing it again..Next time I'm insisting on a "FIX"!

 

I need to resurect this thread since my 09 hemi (95K) started acting the same way when towing for a longer time. The CEL goes away after driving without a trailer for a few days. P0740 stored.

Did you every had to do anything more than just a reprogram? Anyone else with this problem and most likely fix?

Thanks

 

I finally got them to replace the torque converter and pump. That fixed it. they tried a sensor and that didn't work. The problem only existed for me when I was towing. Not locking up into 5th, even when when going down hill. When not towing it was fine. I took the mechanic for a ride with my trailer and showed him what it was doing. He thought the sensor on the side of the tranny....nope, not it...
Thank God for powertrain warranty..

 

I need to understand what gear is best to select (while towing).

This weekend will be my first time towing with a RAM. Going on a 200 mile round trip in the flat lands.

After reading many post it is confusing (for me) Lol.

It appears that some only use TOW/HAUL during towing:

• NEVER
• ALWAYS
• Only while going down grade for engine braking.
• TOW/HAUL and 4th gear selected.
• Only 4th gear selected.
• TOW/HAUL and 5th gear selected.
• Only 5th gear selected.
• TOW/HAUL and gear selector in Drive.

I am asking here because 5th gear overdrive engaged is mentioned in the above post.

I am not interested in best fuel mileage...only best performance, least worry hahaha.

Thoughts?

 

I use it when I feel the truck needs it. I haul my 3 place snowmobile trailer with three sleds in it in regular drive. If I am at a point in the trip where it gets hilly and seems to shift alot, I'll hit tow/haul and let it decide from there. I sometimes us tow/haul going down hill to help with engine breaking.

 

I also only use it when the truck is telling me it needs it. If it is hunting then I switch it into tow/haul and let it figure out the gears. Most of the time pulling my 5000lb+ boat, I do not have to run in tow haul except up large hills. On the rare occasion that I need to deal with long downhills then I'll use the manual selection, but not necessarily have it in tow/haul.

 

I tow a single axle 3500 lb max camping trailer that has a lot of wind resistance. With the 3.21 gears, I always use tow/haul and mostly lock out the 2 overdrives. At 1:1, the torque converter locks up readily and at 65 MPH the RPMs are at 2,200. Sometimes I allow the first overdrive depending if the wind is calm or I have a tailwind. Last trip of about 600 miles RT, I got a hand calculated 11 MPG. What I like about getting the TQ to lock up, is that the trans temps are a lot cooler.

 

I had this at 80k, they had to replace the torque converter under warranty. Would have been $6000. I had no symptoms but the occasional code