Hey everyone! Please excuse my ignorance :|, I don't often tow heavy enough or up and down hills enough to turn off my overdrive function. I'll cut to the chase. I have a 2005 F250 4x4 with an automatic transmission. We are buying a boat that is big enough that I figured it is time to learn to use the overdrive function.
From what I understand, overdrive is always on when driving normally, but when you turn overdrive off, it limits the gears that the truck utilizes.
Can someone please explain to me when I should consider turning off overdrive? How does the truck run in overdrive in comparison to without overdrive? Is there a max speed I can go without overdrive on? Any information regarding overdrive usage would be greatly appreciated! Thanks in advance.
Do you mean the tow/haul mode? If so, I turn on tow/haul each time I'm hauling a trailer. It adjusts the shift points and helps with braking tremendously. At 60 MPH, I think I'm running about 2k RPMs (I have the 4.10 rear) which is the same when tow/haul mode is off. I don't believe tow/haul shuts down overdrive but rather changes the shift patterns and like I said, it uses the transmission for braking too.
On stock tuning, you can't really turn off O/D. It can be done with custom tuning, but it's not really necessary for most applications. The Tow/Haul button changes shift points and pressures to allow for more RPM while getting a load up to speed or up a hill, like @jd4010 mentioned. Depending on the load you're hauling and the terrain you're running, the button may or may not be necessary. If I'm not hauling over 5k, I generally don't use it, unless it's to help slow down or stop.
I use mine when I want engine brake instead of normal brakes when empty or loaded. I don't tow heavy enough most of the time to need all the RPMs it gives me so I usually engage tow/haul when I'm about to get on the highway other than that it's off most of the time.
Thanks for the responses guys! So the tow/haul mode is something I can just press and use at any speed, I don't need to slow down or stop to engage it? The engine braking will definitely be very useful when towing the new boat.
I currently run a custom tune by Quicktricks, and also have one I use by Innovative. Running either these shouldn't effect the usage of the tow/haul mode, correct?
Correct....just turn on/off as needed. No need to slow down, etc. For me, I typically turn mine on at the start of a haul so it stays on the whole trip. Others turn it on/off for braking, etc. But nothing special needs to be done to use (or turn off).
Running a custom tune shouldn't really affect the actual usage of the T/H button, but those custom tunes could be written to change what actually happens when it's used. If you didn't request something when getting the tune then it will likely work just like stock with maybe some minor shift point differences.
I "believe" I remember someone talking a tune that disabled O/D and TC lock when T/H was active.
If you're only running 50-55mph in T/H mode, you are probably never getting into O/D and/or TC lock. That's why your RPM falls when you turn it off. That's also why the EGTs run a little lower since you're moving more air through the system with less load on the engine. This only works to a point though. Excessive RPM do to a heavier foot can make the EGT go up too. You have to find the right balance.
On a reasonable load and depending on the terrain, you'd probably get better mileage with T/H off, but you may risk toasting the transmission clutches if you're lugging it too much. Again, you have to find the balance.
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