Towing in tow-haul around 2500rpm

[CookJ]

I know there is probably some information on this somewhere but did not have the time to search this morning. Would I be doing an injustice to the drivetrain if I towed in the tow-haul mode pulling approximately 7000# while cruising around 60-65mph (2400-2500rpm)? I'd like to get the egt's down and the rpm's up abit. Depending on road conditions and climate, egt's are typically around the 900-950F mark and turning about 1800-1850rpms when towing in OD. I know fuel mileage will be down some if out of OD while towing but if it is better on the truck, I'll sacrifice a little more at the pumps. As I understand it, the "sweet spot" for these engines is around the 2200+rpm range. One more thing, we normally travel short distances (100-400 miles one way). Any information or advice would be appreciated. James

 

[CKelley1]

the motor will last longer at 1800 it will last longer at either rpm than the truck and especially that auto trans, our 91 has over 850,000 on it loaded with 6,000 in the bed full time and pulls 25,000 falf of those none of our 12 trucks have been overhauled and the only one that has blowbuy was caused from a K&N air filter

 

[mberry]

No you will not hurt anything. However, 900-950 EGT pre turbo isn't that high. Is your probe pre or post turbo? The '03 and up can take 1300F all day long. The "sweet spot" is still around 2000RPM.

 

[CookJ]

Appreciate the info guys. I can see a turbo and/or gears in the future.

 

[CookJ]

After posting and leaving work yesterday, it occurred to me I used the wrong tach numbers. Around 65mph in OD i'm actually turning 1675-1700rpm; don't know where or why I came up with 1850 (must have still been asleep!) I know towing 7000# at this range is nothing for the mighty cummins, but I believe over time it will take a toll on the transmission, as it does want to hunt from time to time at this speed. thanks

 

[mberry]

Can you be more specific on the "from time to time" issue? If it's doing it on flat ground, then I would agree that locking out the OD would be good for longevity of the transmission.

On the other hand, if it's only "hunting" on hills or grades and not flat roads, then it's doing exactly what it is supposed to and won't hurt anything unless it is hunting excessively.

 

[CookJ]

Can you be more specific on the "from time to time" issue? If it's doing it on flat ground, then I would agree that locking out the OD would be good for longevity of the transmission.



On the other hand, if it's only "hunting" on hills or grades and not flat roads, then it's doing exactly what it is supposed to and won't hurt anything unless it is hunting excessively.

It's primarily on grades, and very seldom at that, and, I agree with you that it's doing what it is designed to do. I have pretty good driving habits when it comes to towing and routine maintenance, but, was curious if there are things I should be doing or could do differently to prolong the longevity of this 47RE. I know these trannys haven't the best reputation out there (as compared to the 48 and newer), but, at 142K she still seems as strong as the day I bought her.

 

[rluft]

I wouldn't worry about pulling 7000lbs at a lower rpm in OD. I always pull in overdrive as long as the RPMs stay above 1600. I read somewhere that below 1600 rpm the transmission doesn't have full hydraulic pressure. I have 140,000 miles and the converter has a little shutter on hard pulls but otherwise transmission works great. My problem is that when running in OD and pulling my trailer the sweet spot is at 75mph and I don't like to tow that fast, 4:10 gears would be nice or an overdrive.

 

[AClayton]

My trailer only weighs in at 5000lbs. ... again , no match for the Cummins,and my egt hovers around the 800 to 950 mark. I tow in OD also and with the torque converter locked... . around 1600RPM. As soon as I come upon a hill and the egt starts to rise, I just hit the OD button to bring in the 1800 RPM zone. I was told at ATS that I cannot hurt my 5-star at all with my few upgrades.

 

[CookJ]

Yea, I hear you, 65 mph is about where I want to be. I'd have to be moving 80mph+ to be at the 2000 mark. As I stated earlier, gears may be coming in the near future. Until then, I'll continue on as I have and not worry about it. I appreciate all the responses. James