Overdrive

**Bothe** · 02-13-2012, 07:54 PM

Could anyone tell me when I should turn off the overdrive? I see my dad turn his off when he goes down hills with his Powerstroke, but he tells me i dont need to mess with it on my truck. I really dont even know what it does. he didnt do a very good job of explaining it haha

**Fordguy77** · 02-14-2012, 04:51 PM

What overdrive essentially is gear ratio that allows your motor to spin at a less than 1:1 ratio to the axle. Which allows lower rpm at higher speeds and increased fuel economy.
I imagine the reason he switchs his overdrive off while going down hill, is because he wants to ease the work on his breaks and allow his engine to do the "breaking".
Its the same concept to some extent to when you down shift in a manual to slow down.

**Fordguy77** · 02-14-2012, 04:58 PM

Personally from my experience the only time I've seen people turn off overdrive is when they are going up hills(mountain passes typically, guess it depends on location and opinions) and don't want to over work the transmission by having it keep up and down shifting, or when there off roading and want to keep the rpm up and in a constant gear instead of that constant switch. Also I've seen it a few times in certain circumstances turned off for brief moments while towing a load. However that's what I have witnessed.

**Bothe** · 02-14-2012, 08:37 PM

Thank you for the info! That actually does make sense because he usually turns it off at the top of the decline and when it starts it go back up is when he puts it back on. We have a little of mini valley's which is mainly what he does it on

**Raptor05121** · 02-15-2012, 08:54 AM

Well if you know what you're doing, you can be selective like that but generall if you turn it off, you should leave it off. It stops the transmission from "hunting" (IE shifting up and down constantly). I use this (Ford renamed it Tow/Haul mode in the early 2000s) on my F-550 Fire Truck. 20K pounds of fire apparatus is a lot to get going and it automatically downshifts when I get hard on the brakes (intersection, turning, etc). Its a nice feature.

**kokeshx4** · 02-21-2012, 09:43 AM

Ur suppose to use it wen ur haulin or towing anything. It saves the tranny wen u pass or speed up loaded. If u would do tht with the od on it would eventually cause the truck to buck and transmission fail.

**JCooper** · 02-21-2012, 06:26 PM

I usually turn my overdrive OFF when driving around town. It keeps my truck with its 35" tires from shifting in and out of overdrive constantly at speeds of 40-45 mph which isnt good for a trans. I will turn it back on when getting onto the highway, however. Not a bad habit to get into if you typically drive those types of incline/ decline, upshift/ downshift types of roads.

My previous truck was a F350 power stroke. It had the tow/ haul mode which does MUCH more. It alters the shift pressures and optimizes shifting while towing... but does not "lock out" overdrive. It will only shift into overdrive when it senses a low enough trans pressure and a high enough speed so that it won't need to quickly downshift again. I think it works great. While towing a heavy trailer, it shifts almost exactly as I would if it were a standard.

**kokeshx4** · 02-21-2012, 08:56 PM

JCooper I understand with the bigger tires tht u would do tht. Cuz urs shifts differently then a standard size tire would. But wouldn't u b able to leav it on n just keep the rpms high enough to keep it from shifting in and out of overdrive?

**Raptor05121** · 02-21-2012, 11:49 PM

Originally Posted by JCooper

I usually turn my overdrive OFF when driving around town. It keeps my truck with its 35" tires from shifting in and out of overdrive constantly at speeds of 40-45 mph which isnt good for a trans.

OD doesnt kick in until freeway speeds (IE: 4th gear). having it off going around town isnt doing anything

**JCooper** · 02-22-2012, 06:26 AM

Originally Posted by Raptor05121

OD doesnt kick in until freeway speeds (IE: 4th gear). having it off going around town isnt doing anything

Overdrive will kick in at speeds as low as 40mph or so if engine/ trans load is low enough. But thanks for trying.

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Originally Posted by kokeshx4

JCooper I understand with the bigger tires tht u would do tht. Cuz urs shifts differently then a standard size tire would. But wouldn't u b able to leav it on n just keep the rpms high enough to keep it from shifting in and out of overdrive?

You are talking about an automatic trans, right? Keeping the rpms up would mean accelerating more.... but then it would upshift anyway. The answer is no.

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