Towing in OD with 48RE

[Mathes308]

I'm pulling an 8000lb travel trailer, I don't know if they trans has been replace or is original, fluid looks great, will be getting AMSoil soon.
The truck LOVES!!!! to pull locked up in overdrive, locks in around 50mph and wont unlock until 40ish. Looking to tow this thing a lot, turning the OD off doesn't work well, seems to take the engine out of its torque range and just suck fuel, does lower EGT's but not much, depending on throttle.
You guys that tow a lot, run in OD?
I was told not to tow in OD with my 2000 ram and 46RE but 200K later, its still stock and still alive. (also still full of AMSoil and a large cooler).
The current truck seems to run cool for transmission temps, just got back, trans rarely see's over 150, will get to 180 up a long grade if the converter is loose. Temp sensor is on the output line from the transmission right before going into the liquid to liquid cooler.

I run higher EGT's easier with it locked in OD, but I just manage it with my right foot, usually runs between 800-1000, 1100 is max at 3/4 throttle, if I go farther it will go to about 1300, but I can tow easily down the highway staying 600-900.
Just doesn't seem feasible to drive across the country in 3rd.

Thoughts?

 

[p-Bar]

What rear end gears are you running ? I towed my 14K 5er 3k miles last year transmission is built valvebody/triple disk .I run a Smarty JR in performance mode . I would let it go into OD when I was doing 70 on flat ground and small grades and when the mph would drop to 65 I would take it out of overdrive . I found it hard in Cali to tow at 55 because OD is lugging it to much Just my .02 .

 

[Mathes308]

3.73 rear, seems pretty happy lugging it, engine is all stock, thinking of getting a smarty jr and towing with it on the 40hp setting, not ready to build the transmission yet, I would like to bump the line pressure up some so it's not as hard on it when lugging the engine, the 5.9 just seems to love the 1400 rpm peak torque sweet spot.

 

[p-Bar]

I like the 1800-2000 range .

 

[cerberusiam]

Always tow in OD, it goes there and almost never comes out unless speeds drop too far for slow-n-go. The engine won't like 1400 rpms with a heavy load and the trans will sure not take it for long. Once the rpms drop under 1800 rpms fueling is drastically reduced, there is no margin for lugging or accelration at that point with a heavy load. The trans will just downshift to get the RPM's up. The TQ peak is well above 1400 on a stock engine, more like 2500 rpms. Tune it and that moves back to around 2000-2100 rpms in most cases.

 

[Todd1113]

Always tow in OD. It will keep your transmission cooler and the tq converter lasts longer. The 5.9 actually makes peak tq at 1500-1600 rpms and stays pretty flat til 3000. On my 06 I have tow/haul mode which locks the converter earlier and keeps it locked and does engine braking. With your 03 you can wire up a switch to lock it just have to remember to unlock when coming to a stop.

 

[AllianceDiesel]

I towed my 5ther about 1,000 miles into a head wind on the interstate and I hated how it shifted in tow mode and with od off. Turned everything back to normal and it shifted awesome. Havnt really had a chance to tow it at highway speeds but Im sure it will be the same. Stock trans and efi live tuning. Cant wait to get a goerend triple disk tq and daves new valvebody

 

[Mathes308]

I was really worried about the stock trans having almost 200k miles on it but have been seeing a lot of guys tow heavier for 3-400k on the stock 48re's.
I'm a big believer in synthetic fluid, cooling, and frequent changes.
Wish I could find info if they have worked out the bugs for Cummins insite for the 03-04's, friend of mine uses it for his school busses with the 6.7 and I could use it if there was programming.

 

[AH64ID]

The advertised peak torque rpms and the real life peak torque rpms will be different, additionally horsepower does play a bigger role than many want to believe. 555 ft/lbs at 1400 rpms (03-04 HO) is 147 hp but 555 ft/lbs at 2200 rpms is 232 hp so that will influence the towing ability drastically.

Advertised ratings are typically obtained on a pull down dyno, meaning the engine is run up to redline and load is increased until it is at WOT. The load then increases and pulls the engine down and the power is measured. 555 ft/lbs at 1400 will not be obtained by driving at 1400 rpms and going WOT.

Chassis Dyno's put the peak torque in the ±2200 rpm range. 1900-2200 is ideal for towing thru rolling hills and 2200-2500 for pulling hills. It is the best combination of hp/tq, speed, cooling and oiling abilities.

 

[cerberusiam]

The 5.9 actually makes peak tq at 1500-1600 rpms and stays pretty flat til 3000.

Not as-installed in the truck it doesn't.

I was really worried about the stock trans having almost 200k miles on it but have been seeing a lot of guys tow heavier for 3-400k on the stock 48re's.
I'm a big believer in synthetic fluid, cooling, and frequent changes.
Wish I could find info if they have worked out the bugs for Cummins insite for the 03-04's, friend of mine uses it for his school busses with the 6.7 and I could use it if there was programming.

Miles are not the problem, the maintenance and use is a bigger consideration. If the fluid changes have been kept up and it hasn't been thrashed it could stll be tight.

The TC will be the biggets problem in a towing situation, they have a habit of failing under hard use. A shift kit plus other small pieces and a TC will likely extend the life quite a bit.

Insite could work but you will have to build your own connector and bench flash the ECU. That requires a subscription to get the flashes and a lot of work for minimnal changes. If you want a custom Insite tune you would still have to pay for it. You are much better off with a Smarty SO-6, cost efficient and effective.

 

[photowrite]

The advertised peak torque rpms and the real life peak torque rpms will be different, additionally horsepower does play a bigger role than many want to believe. 555 ft/lbs at 1400 rpms (03-04 HO) is 147 hp but 555 ft/lbs at 2200 rpms is 232 hp so that will influence the towing ability drastically.

Advertised ratings are typically obtained on a pull down dyno, meaning the engine is run up to redline and load is increased until it is at WOT. The load then increases and pulls the engine down and the power is measured. 555 ft/lbs at 1400 will not be obtained by driving at 1400 rpms and going WOT.

Chassis Dyno's put the peak torque in the ±2200 rpm range. 1900-2200 is ideal for towing thru rolling hills and 2200-2500 for pulling hills. It is the best combination of hp/tq, speed, cooling and oiling abilities.

Great post and real-world experience...

One only needs to pull/haul a moderate to heavy load and play with the rpm, gears, and accelerator to confirm how much better an outfit can perform with a little higher rpm, though often with a reduction in mpg.

 

[Mathes308]

I would love to put in a TC with less slip, the stock one feels wrong, way too loose, makes a pile of heat. Locks up nice and firm, does so quickly, drives like a new one should, just too much slip when unlocked.
It just scares me to put a $1200 converter in front of a high mileage trans, although it would make it a much better driver.

Towing light, 16-1800 rpms is nice, real heavy and 19-2200 does sound better.