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Cool, Tight, & STRONG....
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Discussion Starter #1
I'm thinking the "shift up" light works really well to help improve your overall fuel mileage.

Before my *tune-up* the truck just wouldn't pull hard enough to use it. The light always came on too soon, and the shift up, would lug the motor way down.

Now, at a normal four way stop sign intersection, if I start in first gear, the shift light has me shifting up to second, mid-intersection, and into third at just through the intersection. Right after, comes the light to shift up into fourth, and the shift up light comes on for the up-shift into 5th gear OD at about 25+ MPH.

My Duke doesn't like it much (OD @ that low of a speed), but he just hunkers down, grunts, and does it.

Do my results equal your results??..:tup:..
 

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Still haven't gotten around to finding out why my shift light doesn't work.......more then likely it's a blown bulb! LOL! I shift about the same as you indicated when you use the light; but not so soon into 4th and 5th gears. I'd say I'm usually doing 35 mph by the time I hit 4th; and 45 mph by the time I hit 5th.
 

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ProStreet
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I've been using the shift light with good results... I am going to start using the 1st-3rd-5th shifting method and see if that improves/worsens economy... before my tune it wouldn't use the 1-3-5 method too well but with the tune, it pulls well...
 

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When that shift light comes on depends on load, probably map and throttle position, and less about rpm, as long as it's not in high gear. If you light foot it it will indicate to shift up early, till no more gears. Floor it and it's much higher rpm.

Skip shifting works better performance wise if you run the rpm up, floor it or not, light or not.
 

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My upshift light depends on the load and also seems to depend on the throttle position.

My 1st gear is useless, but at the same time the truck doesn't like starting out in 2nd. So basically in 1st the shift light comes on as soon as I get moving. From there on out, the light comes on depending on the load and also how hard I am accelerating. It would come on quicker if I was driving on the road, or wait longer if I was romping onto the highway. Ive gotten used to when it comes on and shift at the right time without having to watch for it. My gas mileage seems to have improved because of it.

But when I drive normally on the road it comes on about the way Eddie describes.
 

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The trucks with a manual trans have a shift light in the gauge cluster at the bottom where the ses light is located. I never knew it myself because I believe the bulb is blown or the previous owner took it out. I knew that 'some' of these trucks had the shift indicator light from driving a friend's older (around '86) s10 with a 4speed many years ago; and just thought that GM did away with the shift light by '91 (year of my truck). After looking real close with a flash light at my dash I saw that there indeed is a shift light! LOL!
 

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Still, I don't know if I could put up with that damn thing flashing at me all the time! LOL!
 

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Cool, Tight, & STRONG....
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Discussion Starter #10
shift light?????
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From Page 2-22 of the Owner's Manual:

"..The onboard computer makes the "SHIFT" light work.
The computer knows how fast the engine is going, and how hard it is working, how fast the vehicle is going, and how far the accelerator is pressed down. It uses this information 10 times every second to decide if you could get better fuel economy by shifting up to the next higher gear.."


The Manual goes on:

"..When the accelerator is released, it is normal for the light to be off.."


And..

"..While accelerating, it is normal for the light to go on, off, and on again, if you quickly change the position of the accelerator. In essence, if you change your mind, it will too and it will respond very quickly..."

And, by reverse, perverse, logic, if any one of the four or so sensors that the "shift light" is using for input signals, has an issue, the light won't work..
 

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One of these days (when it's not so damn hot out!) I'll tear my dash apart and find out why the light doesn't work. I have a hunch that I am already shifting when the light would come on though! LOL!

btw, do you think that running a different size tire then stock would throw the shift light off?
 

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Cool, Tight, & STRONG....
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Discussion Starter #12
btw, do you think that running a different size tire then stock would throw the shift light off?
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BINGO!! This is what I've been TRYING to say!! Not only does fooling around with heavy, wide tires throw off the shift light, but it messes up the ECU via the DRAC module. We have seen (in the Owner's Manual) for the first time, the information processing *rate* of the OBD1 brainbox. "10 times every second" I would suppose it is like the old saying of: "Garbage in, garbage out"..sure, go ahead and put those big fat tires on the little truck..but do not expect it to ever approach
OE fuel mileage. Or, performance. IMHO..
 

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Well, all I know is that my fuel mileage was actually higher with the 235/60/15's then with the 235/60/14's.......AFTER I recalculated for actual miles. Prior to figuring out how to recalculate for actual miles, it 'looked' like it was the other way around; but not by as much difference. Like I mentioned earlier (maybe in one of our other threads) I plan on putting the 225/60's on my 15's soon, which are only .4% difference in height from the stock size 14's.
 

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Cool, Tight, & STRONG....
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Discussion Starter #14
Well, all I know is that my fuel mileage was actually higher with the 235/60/15's then with the 235/60/14's.......AFTER I recalculated for actual miles. Prior to figuring out how to recalculate for actual miles, it 'looked' like it was the other way around; but not by as much difference. Like I mentioned earlier (maybe in one of our other threads) I plan on putting the 225/60's on my 15's soon, which are only .4% difference in height from the stock size 14's.
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Over on the Ecomodder Forum they speak of LRR tires.

LRR tires stands for Low Rolling Resistance tires.

Somewhere on the 'Net there exists a list of these tires.

I wonder how many 45-50 and 60 Series tires are on that list??

A low profile tire can be the same exact height as OE, but if it won't roll or is a heavy sucker (vs. OE) then what??
 

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I hate the shift light. I guess thats a plus of using automatic clusters in 5-speed vehicles, you dont have 'em!
 

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Boozebag
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MAN, you guys are dedicated!! :haha::p
I want PROOF of a 40 MPG Duke!
Mine sure as heel doesn't get that.
 

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LOL! I honestly do not see hitting 40 mpg with mine unless some radical aero mods are done (which I'm not about to do). But, I am just about at 32 with less then half of my miles being hwy......on half the first half of a tank.
 
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