O/D on or off?

[2k1exsport]

this is how i normally use OD normal street use i keep the OD off but when i get to the highway i turn OD on for better gas mileage. i was told to do this by my father. i also heard that less engine wear occurs when using OD at high speeds. is this true and what exactly is the point of OD? thanks

 

[Robb]

OD is just a higher gear which allows the engine to run at a lower speed while the wheels turn at a higher speed (ie, it's perfect for highway driving). Around town, you might as well leave the OD on. IF the truck can use the higher gear (ie long stretches of around 45 mph roads), it can switch into it. The only time you really need to turn the OD off is when pulling, off-roading, or traveling mountain roads.

 

[2k1exsport]

thanks alot one more question though...... with the OD off, will i have better acceleration?

 

[Jason_25]

Do a search for this, there is so much info on it.

 

[Robb]

No........OD doesn't affect lower gears at all. It only comes into the picture if the truck senses that you are steady driving at a higher speed. THe only time it needs to be cut off is if the truck needs all the torque it can get (since the gear ratio of OD doesn't allow for any real torque). OD is just like if you were driving a manual in 3rd gear, and you were steady driving and the engine is running high rpm, so you shift into 4th. That is all OD is.

 

[Jason_25]

Actually I think with the newer elctronically controlled auto trannies O/D can be applied to 2nd and 3rd with the 4R55E, and also to 1st, 2nd, and 3rd with the 5R55E. Correct me if I am wrong here.

 

[2k1exsport]

ok thanks alot

 

[X24]

I have the SOHC ( I dont know the numbers of my tranny). I havent quite figured out how the O/D works. I know that if I'm in 5th (O/D) and I hit the button it knocks it down a gear but if I leave the O/D off, it still seems to up shift again. I know I have 5 gears but when I am accellerating it feels like 6. I can really feel the shifts between 1,2,3,4 and then after in 4th for a little, just when you think its gonna shift to 5th the RPM's drop but it doesnt shift to 5th. It shifts into 5th a few seconds later. Does anyone with the SOHC know what I'm talking about? It happens to me when I am still on the gas in 4th gear still increasing speed. The RPM's suddenly drop (still increasing speed through out the drop) and then it shift to 5th about 5-10 seconds later. I'm confused.

 

[Jason_25]

That's your torque converter locking up before making the switch to O/D.

 

[X24]

is that normal?

 

[TPLYNCH]

Actually, the torque converter "shift" occurs between 1'st and 2nd on mine. Always feels like it's a 6speed...

 

[X24]

can someone explain what the torque converter is please.

 

[offroadkc]

I went rounds with my brother-in-law on this so the frustration has been building. :fire:

OD is not magical it is just an other gear.
A 3 speed auto with OD is just like having a 4 speed auto with an extra high 4th gear. That is all it is.

Turning it off when driving around town will not make your engine last longer, it will not improve performance or milage. (And it is not a passing gear)

AAAAGGGGHHHH!!!!!:frustrate




Thank you I needed that.

 

[Alec]

The torque converter is a fluid coupling between the engine and an auto tranny. Here's a good (long) explanation and video: http://www.howstuffworks.com/torque-converter.htm

Basically the torque converter allows slippage between the engine and tranny (kinda like a clutch) but can also multiply torque via the fluid. It will eventually 'lock up' at a certain rpm, producing a 1:1 ratio between engine and tranny. This is what you may feel as an additional shift.

www.phrtv.com also has some info and animations.

 

[X24]

thanks alec

 

[Robb]

OD is not magical it is just an other gear.

That's exactly what I thought! Are offroadkc and I crazy?

 

[utmustang88]

here's a question regarding o/d on or to leave it off? i saw that someone said it didnt make a difference.
i just bought a 96 EB with 69k and i have been reading that these trannies have a bad O/D gear and will cause the tranny to fail. as of right now the tranny fluid has been changed 2times in its life and seems to shift very nicely, but i shall keep my ears peeled for any weird noises.
if i leave the o/d off around town so it does not shift back and forth 1000 times from o/d to 3rd; wouldn't that put less stress on the actual o/d gear, therefore causing my tranny to last? has this been discussed before? i have been searching for more threads like this wether or not to leave o/d on or off...and this is the 1st one i came upon.
i look forward to talking with fellow explorer owners and sharing stories and lending tips and tricks. take care all

 

[Alec]

Welcome!

Unless yours shifts in and out of OD very often then just leave it alone. OD should engage between 45 and 60 mph (normal acceleration) depending on axle gearing.

 

[Bill Kemp]

I have to think that around town or on a stretch of road with hills & turns where the OD is continually shifting that turning it off is the best thing to do.
Keep changing that trans fluid ea. year and you should have no problems. I'm at 105,000 and the trans. still feels tight. I put a drain plug in the trans. pan which makes the annual change a lot less messy.

 

[Majisto]

I love my 5R55E It's so much smoother than the POS AX4N in my Taurus. I can brealy even feel the tranny shift in the X. But yes I know what you mean about the tranny going into O/D. I'll be accelerating in 4th and the RPMs will drop quickly and the pedal will vibrate pretty roughly. I know it's in overdrive when the pedal vibrates on acceleration