I hope that it is not too inappropriate to post this in the 7.3 PSD portion of the website. The proper place would seem to be in the "Toy Hauler Towing" section, but after reading every single topic within that forum, decided that I would like to hear the opinions of specifically 7.3 owners.

I have a 1995 F350 2WD dually 7.3 PSD with an E4OD transmission and 4.10 rear end. When towing a small 12 ft enclosed trailer with a 1,500 lb payload, I do not turn the OD off. Everything works just fine whether on flat land, or in the Smokies.

In the next month or so, I intend to pull a 29 foot toyhauler that weighs about 7,800 lbs empty. Inside of it, will be a motorcycle that weighs about 1,140 lbs, along with a couple hundred pounds of general "stuff". A weight distribution hitch and an anti-sway device will be used.

When driving this truck with the OD on, the engine is doing about 1800 RPM when at about 57 MPH. When driving this truck with the OD off, the engine speed increases to about 2600 RPM at the same MPH. I have been reading several conflicting pieces of advice, from owners of different brands, and different engines. Some say to run the engine at a faster RPM to save the transmission when pulling a toyhauler. Others say to run the engine slower, as a faster RPM will overheat the engine manifolds and make other bad things happen. The comments generally are not from 7.3 owners, so I thought that I would post here, and see what thoughts may arise.

Any pieces of advice?

Thank you

 

Do you have a manual handy? Where is the maximum torque for your engine?

I would think it's closer to the 1800 RPM value.

Also, if the OD is ON, and you start lagging the engine, it should downshift to increase RPM for you anyway... right?

Here's what I found:
7.3L Power Stroke Diesel Specs & Info

Peak Horsepower:
• 210 hp @ 3,000 rpm (intro horsepower rating, 1994 MY)
• 275 hp @ 2,800 rpm (peak horsepower rating, 2003 MY)
Peak Torque:
• 425 lb-ft @ 2,000 rpm (intro torque rating, 1994 MY)
• 525 lb-ft @ 1,600 rpm (peak torque rating, 2003 MY)

For pulling the TH, I'd think you'd want torque over power, so the lower RPM would give you better pulling performance. Just my opinion, though.

 

The truck is more than capable of towing that weight in OD or out in stock form.

Regarding RPM, diesels do not like to be "lugged" up a hill. In stock form and with all system operating as they should a stock 7.3 diesel will not have EGT (exhaust gas temperature) issues. The comment about the trans is irrelevant, to save a trans you do not wanting it shifting in and out of gear constantly pulling a hill, rpm is not going to hurt it

Your motor will appreciate rpm when pulling a hill. slowing down and staying out of OD pulling heavy up a hill will have you better off than lugging in and out of OD. Its not any different than a gas motor in that respect. Do not over rev the motor thought when shifting maually on the stick out of OD. Put it to the floor and wait for the downshift, once you shift out of OD you can turn it off rather than shifting it manually before catching the shift. Make sense?

More rpms flow more exhaust gasses in turn spooling your turbo forcing more air flow into the motor, this will run cooler in the EGT department as well.

To put it simple, you can put the pedal to the floor towing the load, it will not hurt anything, minimizing shifting back and forth is what will help your trans, the 4.10s are what you want for towing. Running a manual I'm near 2500 rpm cruising at 70, towing or not in 5th gear. I tried to explain this in a high level approach.





A couple of cheap (cheap is relative when it comes to mods on a 7.3) modifications for the truck that will help when you up-size your to your toy hauler are an intake and downpipe/exhaust upgrade. Diesels perform much better when they can breathe, (gassers do too but not on the same magnitude of improvement) The pancacke downpipe on the OBS trucks is fairly restrictive and is one of the first things to go.

Link to both if you ever get curious, there are a ton of options out there, just stay away from K&N intake filters:

Riffraff Diesel 6637 Ford 7.3L Powerstroke Intake Filter Kit

Diamond Eye 4" Turbo Back Exhaust - Ford 7.3L (94-97)

 

I turn the OD off when on back roads, going up and down hills, and generally staying under 55mph. On the main roads where I can open it up to 60 and above, I run it in OD.

 

OP, i'm still learning the ropes when it comes to towing as well but here are some pointers i've learned so far.

1. Buy gauges, and a BIG transmission cooler. You want to keep your transmission cool, and you want to monitor all of your temperatures to know exactly what your temperatures are.

2. Don't be afraid to rev the 7.3. As long as all of your gauges are showing that you're in the clear you can pull at 3,000 RPMs all day long.

3. As for using OD it comes to a term that i've seen coined here as "gear hunting". If your trans is constantly shifting in and out of OD, lugging for a second, then shifting, then going back into OD, then lugging, then downshifting, etc lock out OD and let it rev until you can comfortable run OD again without it lugging.

Other than that enjoy the ride!

 

I had my trans rebuilt and the guy asked me (not John Woods) if I use OD. I said sure but I use common sense.

 

Thank you for all of the thoughts.

BTW - The sticker on my valvecover says 215 hp at 3000 rpm.

 

You want to stay in the boost towing a grade...

 

Yea 215hp that's what the sticker says. At the wheels you might be making 150.

that's all mine makes lol

Get gauges including trans temp and be prepared to get a trucool trans cooler. The factory towing cooler is woefully inadequate.

 

As others have said and my owner's manual too, tow in overdrive unless and until it starts shifting back-and-forth between third and forth (OD), at which time push the "off" button on the shifter and stay in third.


If the RPMs get too low under heavy load in the hills, the exhaust gas temperature gets to the maximum 1250F very easily. Downshifting to raise the RPMs brings the EGTs down like magic, which means your engine likes the extra revs.


When increasing the RPMs, the engine oil temperature begins rising due to the extra friction created by the additional engine speed. Everything's a tradeoff

 

I made 207 at the wheels at RRE a couple years ago. Pretty much bone stock except intake and exhaust

 

X2, what he said.

 

I have 95 7.3 AND THE tow/haul or overdirve button doesn't even work. I have never worried about it especially since I have 410's also. Run it and forget about it, it will shift in and out as needed.

 

Thank you everybody for taking the time to reply!

A short update. Two days ago, I had the opportunity to tow some equipment for my company, so I used the experience to try to learn something.

I connected a light duty 14 foot two axle utility trailer to my truck and left to go to the equipment pickup point which was 67 miles away. The roads were mostly county highways, and were mostly hilly. When not going through a small town every 10 miles, the truck velocity was kept at a rather constant 55 mph. OD was left on for this portion of the trip, and a full front fuel tank was used to supply the fuel.

At the pickup point, about 4,400 lbs of payload was added to the trailer, the OD was turned off, and the rear fuel tank was used to supply the fuel for the return portion of the trip. The original route was now reversed.

Winds were light and variable. The elevation of the starting point was about 1200 msl and the elevation at the pickup point was about 900 msl. Temperatures were about 20F warmer on the return trip than on the initial trip.

At the end of the trip, both fuel tanks were refilled at the same gas station and pump as prior to the trip. The front tank was able to take 3.8 gallons, which implied a fuel consumption of about 17.6 mpg for the initial trip. The rear tank took 3.7 gallons, which implied a fuel consumption of about 18.1 mpg for the return trip.

Of course it is silly to be calculating mpg to the decimal point, when this was a loosely put together experiment, with lots of unaccounted for uncertainties. However, the point of it all, was to see if there would be a gross fuel consumption change by not using overdrive.

In this instance, there was not.