Transmission Complication
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Junior User
Joined: Dec 2004
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Transmission Complication
Hi there, just wondering if I can compare with someone else...I have an '03 F350 CC DRW 4X4 with 6.0L and 3.73 gears. When traveling at 60 MPH the rpm's are showing 1750. I can turn the tow/haul button on and nothing happens, so I think my tranny isn't shifting into overdrive...Is this normal? The truck is stock except for a little larger tire size(255/85/16 instead of 235/85/16) Thanks!
Lead Driver
Joined: Sep 2006
Posts: 5,665
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From: Cartersville, Ga
At 60 mph in tow/haul, the truck will shift into overdrive on relatively flat ground if it feels it can go into it. Once in over drive with tow/haul activated, it will kick it out of overdrive when speed gets to 55mph or you just start struggling it will kick in before 55mph
Senior User
Joined: Mar 2003
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My understanding of Tow/Haul is that it is a shifting strategy that makes the truck keep higher RPMs as needed. It will downshift out of overdrive easier than usual and will stay out of OD longer than normal. Also, downshifts when coming to a stop or going down hills to help you slow down.
Senior User
Joined: Sep 2006
Posts: 253
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From: Santee, CA
As is implied above, you may be thinking of the 4R100 that was previous to the TorqueShift and used on the gas truck. My old 96 460 powered truck was like that. The button was used to allow or not shifting into overdrive. In the TorqueShift, it is not that simple. As you state, it changes the whole shift strategy but still allows overdrive in either mode. Your speed/RPM sound just about right compaired to mine, and I am running the same gearing. If crusing at that speed and you press the Tow/Haul button, it does not downshift unless you are pulling pretty good. However, it will downshift much easier if you get on the throttle. Try it both ways and you should see the difference.
Lead Driver
Joined: Sep 2006
Posts: 5,665
Likes: 164
From: Cartersville, Ga
Same here.
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Junior User
Joined: Dec 2004
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Thanks, guys, just wanted to make sure everything was working right....also I put the new tires on a couple of months ago and I noticed that the speedo or the rpm's didn't change with the larger tires. Is there some sort of compensation for that in the PCM?
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Lead Driver
Joined: Jul 2004
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From: Foothills, CA
Do you have a GPS? If so, get on a level stretch of highway and set cruise on 60 on your truck speedo, then check your speed via GPS. My speedo reads 1-1.5 MPH less than GPS speed is -- probably the most accurate speedo in any vehicle I have ever owned!
I just mentally account for my error, but there's not much to account for -- mostly when I'm towing with a group and everyone says "65", of course you end up adjusting to whatever all their "65s" end up being anyway...
Lead Driver
Joined: Jun 2007
Posts: 6,757
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From: Corvallis, OR
Your RPMs are reading correct, but your Speedo will be off by the difference in tire size. The only way to calibrate the speedo is with something that communicates with the ABS module (like Ford uses) or with one of the little conversion modules like the Superlift TruSpeed.