i know this has been asked many times, but I dont have time to look for this right now.......which is better on gas, O/D on or off? It seems logical that having it on would save gas because the engine would be running at lower rpms. Am I right?

 

OD only affects speeds over 45 mph

 

ok, so if I'm going over 45, its better for gas to have it on or off?

 

it's 35 mph. Go 35 then turn o/d off the rpm range jumps up by about 2k.

 

where do you get that info???
according to the 92 FSM the VG shifts into overdrive @ 62-66 mph (half throttle)
the VE does it @ 71-76 mph (1/2 throttle)
Both specs are in comfort mode obviously full throttle or power mode will raise the speed at which it engages.
the od on or off doesn't change shifting range unless your trans is malfunctioning.

 

I hate to argue, but speed has nothing to do with it. The tranny shifts at certain RPM points. You can be doing 30MPH and be in O/D. Try turning it off, and watch the tach jump. As soon as you let off the gas in 3rd, it goes to O/D, regardless of speed.

 

Isn't the simple answer to the question that O/D stands for overdrive - which is 4th gear on the 3 speed automatic.

Just as you wouldn't typically lug your engine down using 4th gear (in a standard transmission) when driving around at 30 mph, you probably don't want your automatic shifting into O/D at 30 mph.

Thus, O/D is intended only to be a highway speed function and, as such, yes will save fuel by allowing your engine to run at lower rpm when driving at highway speeds. I don't recommend using it when driving around town (i.e. 50 mph or less) because I think it puts additional strain on the engine by trying to get torque when below the optimum rpm range.

 

You should hate to argue, I pulled all of that info out of the FSM. you know that book that is about 1000 pages long and was put out by NISSAN
not to mention the fact that I am ASE certified and I sold transmission parts exclusivey for a while.
Your misconception on the rpm is because the speed is partially dependant on engine speed (the other part is converter slippage)
You want to keep going?

 

I found this in less time than it took to type your question.
http://auto.howstuffworks.com/automa...nsmission8.htm

 

Cool site! Thanks Jeff!

 

Okay I didn't read your first post clearly. I see the part where you listed the speed it shift's into O/D, and where you state at 1/2 throttle. Obviously driver input also has an effect as to where the tranny shift's at.(in regards to speed.) (And I will admit I should have phrased"speed has nothing to do with it" differently!)

 

Glad we cleared that up.

 

yea, thanks Jeff, thats a helpful site

 

...It doesn't shift into o/d at 30mph...nor does it shift at 60 something, unless you're giving it heavy throttle. At about 35-40 is the point where the overdrive gear engages under normal driving situations. Just like VG Ill ridah said.

Now, I would assume the lower engine speeds in overdrive would be more economical. I don't see how they couldn't be (?)

 

look up at post #5 in this thread.
You'll see the source is clearly quoted.

 

Yeah, haha, sorry about the overlook.