Truck isnt happy pulling trailer

[Jackpine]

It's possible you might have gotten more views in the F150 section, but I think it belongs here, and, once you create a thread (or a post), you don't have the power to delete it! (I expect that's because it can have a bearing on other posts in the thread.)

Anyway, glad you posted a picture. I suspect your trailer is 8 feet wide (standard width). Looking at the picture, it might be 7 feet high? (Box height, and 1 foot off the road?).

Now, with a class IV trailer tow package, the frontal area limit is 60 square feet. If your trailer is 8 x 7, you are at 56 square feet and very close to the limit.

Your tires have a 33" diameter (unloaded). If I were to mount your rims and tires on my truck with its 3.73 gearing and 32" tires, it would reduce my effective gearing to 3.62. I don't know what your stock tires were, but it's clear that your effective gearing is now much less than 3.55.

I'm guessing the empty weight of your trailer is 3-4000#?

In any case, I think you are very close to the tow limit of your truck. If you can afford it, changing your axle gearing to 4.10 would make towing a lot more enjoyable. (Both axles if you have 4WD).

Now, why were the RPMs in 3rd gear with O/D off higher than they were in 3rd with the O/D on? Probably, as Westcoast mentioned, your Torque Converter was unlocked in the higher RPM case. It would take very little additional load on the engine to cause the TC to unlock, which it does to provide you more torque. I think that at the speed you were traveling, your engine load is right at the "breakpoint". Again, higher gearing will help this situation.

And, if you want to talk to someone at PHP, try their "live chat" feature you can sign up for on their webpage. Their phones are ALWAYS busy and they really don't take phone "messages". But, if you keep trying, you'll eventually get through (you may become an old man first though).

- Jack

[Longshot270]

Just curious, have you tried using the comm gear PID while towing? One common misconception is the difference between 4th gear (overdrive) and 4th gear with the torque converter locked (locked overdrive) and then the locked/unlocked 3rd gear. Sometimes you think you are dropping out of overdrive and it is just the torque converter unlocking. Usually there is about a 400 rpm difference between OD and locked OD but could be more if you are towing. If your torque converter is locking just a bit too soon you can move that locking point back in your custom options menu.

[mcwilly]

Originally Posted by Longshot270

Just curious, have you tried using the comm gear PID while towing? If your torque converter is locking just a bit too soon you can move that locking point back in your custom options menu.

Seeing as I have no idea what you're asking, I'd say no I havent tried that. I've looked around the custom menu options but I havent made any changes. First thing I need/want to do is find out my tire size in mm so I can adjust that in the custom settings.

[Longshot270]

Originally Posted by mcwilly

Seeing as I have no idea what you're asking, I'd say no I havent tried that. I've looked around the custom menu options but I havent made any changes. First thing I need/want to do is find out my tire size in mm so I can adjust that in the custom settings.

You can use 2580 as a close starting number. To get it dialed in perfectly get a GPS and clear the odometers on it and your truck. Drive at least 10 miles and then use this little formula: GPS odo/truck odo X tire size (2580 if you program it in before you go).

To pull up the PID for the commanded gear go to settings, display, and then scroll through the list for "COMM GEAR", press enter. Then when you go back you'll see which gear the truck is currently supposed to be in. When you get up to highway speeds you'll see a little lock icon. That means that your torque converter is locked. Then next time you pull your loaded trailer look and see if having the shift/lock points raised or lowered would help. They move in increments of 1 mph because the part throttle shifting is dependent on speed and engine load. If having them raised or lowered would help then you can move them next time you reprogram your truck with the custom options menu.

[mcwilly]

Well, I got a hold of PHP this afternoon. I didnt get to speak w/ Bill directly but I mentioned my problem and he suspected it's exactly what you guys were saying it was w/ the TC locking and unlocking.
Longshot, I found the option in the setup and have it as part of my display now so I'll check it when I pull the trailer again.
Thanks guys for the advice. Hopefully I'll get it tweaked enough to make pulling the trailer a little easier. Think I'll wait till after I receive my custom tunes before I do any major tweaking.....I've got a couple of weeks before I have to pull the trailer with a full load again.
I asked that they point Bill in the direction of this thread...hopefully he'll get a chance to read it.