One more post for the night, I am still trying to figure everything out on this truck. I have had it a few months, but have not worked it very hard yet.
2005 F350 6.0 diesel.
This weekend we pulled the camper out for our first trip of the year. I have pulled the camper with this truck once last fall, but that has been all so far. Just like I usually do with all vehicles when towing I pushed the button to shut the overdrive off and switch to trailer tow mode. I did that before I left my yard. When I was driving up the street from my house the truck did not seem to want to shift at all. It wound up to about 3000 RPM's and still wasn't shifting. It was not a hard pull, and I was not on the throttle hard. I let off a little to see if it would shift, but it didn't, 3 and 1/2 blocks to the highway. When I turned onto the highway it still didn't seem to shift. When it wound up to 3000 RPM's again I pushed the button to turn the OD back on. Then it shifted like normal. This was all flat ground. When I started out of town the highway runs up a long hill, not very steep but a couple of miles of steady incline. It shifted fine through that with the OD button on. When I got up to highway speed I pushed the button again to shut the OD off and everything was fine while traveling down the highway. After about 40 miles I turned off of the highway and again it didn't want to shift. At about 2500 rpm's I pushed the button again and it shifted fine.
On the way home today it did the same thing. With the OD turned off it wound up to about 2800 RPM's and shifted, but it shifted hard. Again it was on flat level ground and I was not pushing hard. I would say I wasn't even at half throttle.
I vaguely remember reading on here last fall that there was an issue with the OD button on these trucks. What should the normal shift points be when towing a trailer? The trailer is a 30 foot travel trailer. I usually pull with the water tanks empty, so the weight is somewhere between 8000 and 9000 pounds. If I pull with the OD left on will I burn up my transmission?

 

No, you won't.

Now for the corrections: There is no way to turn off OD on your truck. Pressing the tow/haul button on the end of the shifter enables tow/haul mode. It does NOT turn off overdrive. It makes the shifts happen at a much higher RPM than with the tow/haul mode off. From your description I'm not sure that anything is wrong.

If you don't like the way it shifts in tow/haul, don't use it. The trans will be fine either way.

 

From what I understand use the OD off button when climing hills to keep the transmission from constantly shifting. You can also use it when decending a hill.

 

Yes, but this truck doesn't HAVE an OD off button.

 

I had to go out to the truck and check it. Your right, it does not have an overdrive off button. My F150 does, but not this one. This one it says tow / haul instead of OD off.
I am not comfortable with winding it up to 3000 to 3500 RPM's in first gear at 30 miles per hour with minimal load on the engine. If I had it mashed to the floor I could accept the high RPM's, but less than half throttle it should have at least tried to hit second gear. If it is safe to run without the tow / haul button pushed then I will just not fiddle with it.

 

What you felt was entirely normal, and is the point of the Tow/Haul button. It's a second transmission program that delays upshifts when accelerating to use the peak torwue range of the powerband, increases engine braking on downshifts, and if you use it with cruise control it will maximize engine braking on down grades to try to hold speed for you. The 6.0 has a decently flat torque curve between 1800-3200rpms. The delayed upshifts keep the engine closer to the start of the peak at 1800rpms when it does shift, instead of shifting back to toe 1300rpm range where the engine makes 100 fewer lb-ft of torque. You aren't going to hurt the engine running it at a higher RPM with no load; the turbo won't boost so excess fuel isn't being added and the engine is running like a large air pump at that point. It's designed to spin that fast, and to do it without a ton of fuel getting added.

You aren't going to burn up the trans up stock with a 9000# trailer unless you do something really stupid to it, using Tow/Haul or not. The trans temp needle on the dash is one of only two that are actually somewhat useful (boost is the other) and basically if the needle moves out of the middle it's on it's way to overheating. This is how the gauge works:
Tow/Haul info specifically for 6.0L w/ 5R110W:

 

Wow, a lot of good information there. Thanks.
My only concern was when I started out. I was on flat level ground, not pushing the engine hard, not pulling hard and it did not want to shift to second gear. I even backed out of the throttle a little thinking maybe I was pushing it, it still didn't shift.
I just have not driven this pickup enough pulling the trailer to know what to expect. I was a mechanic for a lot of years but do not know much about diesels. In fact the last diesel pickup I owned was back in the early '90's when we had a 1989 F250. After that pickup I swore I would never own another diesel, but towing our camper was just wearing our old expedition out.

 

I've been driving this truck for almost 10 years, and the way it holds first really long in Tow/Haul can be a weird feeling, you can make it feel almost like a manual trans holding 1st almost to the redline and make the truck buck by bouncing the pedal. Just have to play with it some and figure out to make it smooth and to not bounce the pedal.

The 6.0 will drive very different from an IDI, mainly because the variable turbo flattens out the torque curve over such a wide RPM band.

Don't give up on it until you play with it some more. It's a stock tuning profile, so you won't hurt anything loaded or unloaded by using it. Next time you get on a downgrade, set the cruise and engage Tow/Haul, it'll automatically downshift to hold the speed you set the cruise at. Saves your service brakes for when you need them on long grades by making the turbo work as an engine brake.

 

I think I will mess with it some more. I just did not like the hard shift when it did finally hit second gear. In my mind a hard shift in a stock vehicle means it is tearing itself up.
It never even occurred to me to set the cruise control when pulling the trailer. I might have to give that a try and see how it handles. With all of my gas pickups running the cruise while pulling a trailer does not work well.

 

You can also use it when decending a hill.

 

I disagree with the concept of a hard shift being bad. Just my opinion but the faster it shifts it would seem that it will spend less time slipping while releasing one gear and engaging the next.

 

Up to a point, yes, that's true. But it is also possible to shift hard enough to break parts. I've done that in a prior career where I developed transmission tunes.

 

I just had a hard time with the hard shift. When I was drag racing we put shift kits in our transmissions to achieve a hard shift, but I also remember broken gears and broken shafts inside of the transmission if we weren't careful.
It will be a few weeks before we can get the camper out again, I will give it another chance to see how it works.
I remember when I was a kid we had an old 76 Ford F250 we pulled a camper with. My dad would always try to use the cruise control when pulling. That truck with the 390 and C6 transmission. Every time it would drop down a little in speed it would shift down and the engine would wind up and start knocking and pinging, then it would shift back to 3rd. It seemed like every few seconds it was shifting and trying to maintain speed. Since then I have never even thought about setting the cruise control with a trailer on.

 

I often tow with cruise on. Newer transmissions are MUCH better about not shifting up and down all the time.

 

I often use cruise when pulling a trailer. Several of my pickups had manual transmissions. When running in hills or mountains the cruise was off for several reasons. Anymore with tow/haul mode I'll run it with the cruise. Unless conditions dictate otherwise.