It is all in your head. Turning off over drive changed NOTHING other than the ability Not to go into 4th.

It is NOT tow/haul mode like the newer trucks that changes shift points

 

It can't be in fourth and first at the same time. It's physically impossible.

 

ALSO remember that when you put the e4od OUT of overdrive, the next time you start the truck, the OD will be turned back on again.

I run my truck out of OD most of the time. I live in the mountains. When I go to the flatlands, I turn on the OD and hear the engine slow down a bit.

(Apologies for the wording. I'm very tired right now.)

 

No, but it CAN fail to shift out of 4th, and still operate at low speed- Try it with a manual transmission some time: you have to slip the clutch & lug the engine to get up to speed: With a torque converter, it is much easier. IF my trans is not shifting out of 4th, and it is sluggish, there is a good possibility it is for that reason. WHen I manually opt out of OD., I DO get a better response. I can run it either way. But one feels more powerful than the other- believe it or not.

Scott

 

For the most part the transmission/computer does a great job deciding when to use OD and in my opinion most should just let it. If it's not doing a great job deciding when to use OD then likely something is out of adjustment or not working right.

However one thing not mentioned here is an aspect of what OD is, why it's not just another gear. In the example automatic transmissions at issue 3rd is direct drive, this means internally the input shaft is directly connected to the output shaft which is directly connected to the engine via the torque converter clutch. Essentially the driveline might as well be connected directly to the crankshaft. This is a little more efficient as far as internal drag is concerned but more important it creates much less heat. Towing or hauling a heavy load at high throttle for long periods in OD can be a good way to overheat a transmission. In such a situation depending on conditions forcing the transmission to stay in 3rd and keeping the RPMs up can be better for the transmission.

As said above most transmissions should do this anyway as needed though. If you can climb a hill with a heavy load at high throttle and stay in OD when 3rd would work at that speed then something is wrong with your automatic transmission controls.

 

or your engine (and or rear gears) has plenty of performance to handle towing the load up the hill while remaining in OD.

chip truck at 8k lbs w/ 3.55's will downshift up hills just empty (when driving under 55 mph)
log truck at 10k lbs w/ 5.13's probably wont downshift up the same hill until fully loaded/towing.

log truck enters od somewhere around 27 mph.locking out od..........ah.id like double over please!


really you don't have much concern about canceling OD unless you have a 302 truck and driving in the mountains.you just don't want them to gear hunt back and forth between 3rd and od that's all.you wont help much of anything canceling od otherwise.it's helpful when coming downhill to help take a load off the brakes.towing in od isn't harmful to the e40d or anything.it's the zf5's iirc that can't handle OD towing.