"Heavy" Towing

[Rockranch]

I have read many posts to this forum and the topic of "Heavy" towing in 6th gear comes up often. I have done a search and have not come up with an explanation of what "Heavy" is. I am hoping that the more experienced members could shed some light on this subject.



I have been using the truck in my signature to haul stuff from my place in Missery to the new farm in Texas. So far I have been using an 18 ft. bumper pull, flat bed utility trailer. Gross weight around 7000 lbs. I doubt that I have come near max on that trailer. I usually run down I-44, through Missery, Oklahoma and Wichita Falls, Tx. I would describe the terrain as rolling hills to flat with a few bigger hills thrown in. I recently acquired a 25 ft. gooseneck, with a 14,000 lb. GVW.



Would I be safe to assume that "Heavy" is relative and must take into account things like terrain? Might 6th gear be usable on the flat, but not going up Donner Pass or some other large grade? Downhill?



I bought my truck, used, about 1 1/2 years ago and am still learning the ropes. Prior to that I have had 1/2 ton gassers and everything was "heavy".



Any help in trying to better define "Heavy" would be appreciated.



Thanks,

Larry

 

[CUMMINZ]

Towing on the east coast up and down I-95 & I-85 with mt 16. 5k fifth wheel I do not consider heavy. Now it is a different story when I run west up into the BlueRidge and pull up and down the Parkway and grades like Old Fort mountain. I then consider 16-17k as heavy. To keep my EGTs down I often downshift to 5th. gear with my auto. Some guys often tow 20-30k and they could better tell you.

 

[RustyJC]

I pulled the 5th wheel in my signature (16,000 lbs GVWR) all over the U. S. in my 2002 ETH/DEE (Cummins HO/NV5600) in 6th gear until September of last year with no ill effects. Of course, the 2002 also had 4. 10 gears, so 65 MPH in 6th was ~2200 RPM, right in the engine's sweet spot. Very few grades (I remember a few going through the Rockies) required a downshift to 5th.



If you find yourself lugging the engine in 6th (the engine RPM is dropping and, even at full throttle, you can't accelerate), a downshift to 5th is required. Ditto if you start hearing gear rattle (torsional vibration) coming out of the transmission. In truth, I seldom used full throttle when towing - when you get a feel for the engine, you'll know when it would be happier with a downshift so it can rev and breathe, especially if you have an EGT gauge.



Rusty

 

[Dick Langendorff]

My father in-law and brother in-law were both big rig truckers. They would always say, "If you can't accelerate, you are in the wrong gear!"



Just the short to the point answer.

 

[AH64ID]

My father in-law and brother in-law were both big rig truckers. They would always say, "If you can't accelerate, you are in the wrong gear!"



Just the short to the point answer.

That's pretty much my rule of thumb as well. I'm not a trucker but I have heard it several times and it makes sense.

 

[Grizzly]

I pulled the 5th wheel in my signature (16,000 lbs GVWR) all over the U. S. in my 2002 ETH/DEE (Cummins HO/NV5600) in 6th gear until September of last year with no ill effects. Of course, the 2002 also had 4. 10 gears, so 65 MPH in 6th was ~2200 RPM, right in the engine's sweet spot. Very few grades (I remember a few going through the Rockies) required a downshift to 5th.



If you find yourself lugging the engine in 6th (the engine RPM is dropping and, even at full throttle, you can't accelerate), a downshift to 5th is required. Ditto if you start hearing gear rattle (torsional vibration) coming out of the transmission. In truth, I seldom used full throttle when towing - when you get a feel for the engine, you'll know when it would be happier with a downshift so it can rev and breathe, especially if you have an EGT gauge.



Rusty

I'm a bit more conservative than that and I'm only towing 11 to 12K. Anytime I'm going up any hill, I downshift into 5th gear and a lower gear if I have to. Also anytime my speed slows down to 45mph, I downshift.



Back in the old days when I had a furd F250 large block gasser I had a tach and a vacuum gauge. When my vacuum would drop to some point, I'd downshift. I can't remember what that point was.

 

[Rockranch]

Thank you for the responses, gentlemen. I understand about lugging and acceleration on hills and when to downshift for the engine. Perhaps I should have been more precise in my question. Let me try again.



My main concern is with the NV5600 transmission. I have read many posts where it was suggested that towing "Heavy" in 6th gear was detrimental to transmission longevity, due to the transmission/6th gear design. As it relates to the transmission/6th gear, what do you all mean by towing "Heavy"?



Thank you for your input.



Larry

 

[AH64ID]

I would say over GCWR, but I am not sure how much 6th is useful at those weights on much but a downhill or dead flat??

 

[Slow Six]

I take it to mean that pulling real hard in 6th is putting full power to it and going down to 14 to 1500 rpm before down shifting. I drive class 8 trucks with the big high torque engines that usaually pull down to the 11 or 1200 rpm range before shifting and usaully try to run at a max of 1450 to 1500. I have a real problem with my truck to grab 5th gear early and listen to it scream at the 2400 plus rpms but I have to do it. I destroyed the sixth gear once which ended up being a $7000. 00 repair. I also blame damage on the "chip" as the increased power allowed me to pull hills and push wind easily in 6th. I now pull a M/S fiver that weighs about 19000 lbs. I am at stock power and I still use 6th for towing but I do not work it hard if pushing high wind or on the long grades. These transmissions are of minimal strength. I would like to see the 6 speed Spicer that is used in FL 60 Freightliners. If I read your truck info properly you are chipped. From my experience all I can say is be careful with the power. It would be a good idea to install temperature guages in the transmission and differential and if temps start rising get the right foot out of it.

 

[AH64ID]

I won't drive with the rpms below about 1900 WOT in 6th, I just use 5th.

 

[JMetzger]

I tow all the time in 6th gear but I am like the rest if it won't increase speed or it feels like it is lugging I down shift. I have the NV 5600 in my 02 with 100,000 but my trailer only weighs 10,000.

 

[AMcCormick]

I remember reading something about 6th not getting oil while on a slight grade in the NV5600?

 

[RustyJC]

My main concern is with the NV5600 transmission. I have read many posts where it was suggested that towing "Heavy" in 6th gear was detrimental to transmission longevity, due to the transmission/6th gear design.

With the 4. 10 gears my 2002 had, you have no choice. You're going to tow in 6th gear unless you want to run a max of 55-60 MPH at redline. As I said, my NV5600 never had a problem with pulling our 16K 5th wheel in 6th.



Rusty

 

[RVTRKN]

If you find yourself lugging the engine in 6th (the engine RPM is dropping and, even at full throttle, you can't accelerate), a downshift to 5th is required. Ditto if you start hearing gear rattle (torsional vibration) coming out of the transmission. In truth, I seldom used full throttle when towing - when you get a feel for the engine, you'll know when it would be happier with a downshift so it can rev and breathe, especially if you have an EGT gauge.



Rusty

Even if your empty, if your engine lugs, downshift! There is a 15% grade grade where I live, although its a short run, my engine will lug empty. Every one has a different opinion on this subject, but when I'm towing, even my lite boat, I anticipate any grade no mater how slight, and you will know before you start the climb, I will downshift to 5th. Its not just the engine you have to worry about, but the trany's overdrive gear as well.

 

[Rockranch]

Thanks for all the information, gentlemen.

 

[SRadke]

My general rule of thumb, if your cruising over 15 lbs of boost drop out of overdrive. Obviously there are a lot of variables in that but if I said don't use more than 150 hp in OD for long periods you'd ask me to quantify it.

-Scott

 

[AH64ID]

My general rule of thumb, if your cruising over 15 lbs of boost drop out of overdrive. Obviously there are a lot of variables in that but if I said don't use more than 150 hp in OD for long periods you'd ask me to quantify it.



-Scott

Not sure that's the best rule for 04. 5-07 trucks, I can build 15 psi at 75 empty on a cold and/or windy day!

 

[CUMMINZ]

Do this with 17,000#s and you call it "heavy towing". Hwy. 276 in NC mtns.



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