Redline shift speed.

[DeanMoriarty]

Out of curiosity, I'm wondering around where the redline for each gear is on a 5 speed 93 2.3 2wd.
I have no tach and I think I shift pretty accurately with the feel of the truck, but I'm wondering if I can't safely wind the gears out a bit higher than I do.
Normally I shift like this; Out of 1st @ 15 - 20, 2nd @ 30 - 35, 3rd @ 45, 4th @ 60.
Is it safe to run in 4th at highway speeds, like when going up a big hill? 5th seems to bog down something awful on the hills, but I usually wait until it gets down to about 60 to down shift, to be on the safe side.

 

[Twizzler09]

Your truck probably isn't geared like mine is, if I shift at peak horsepower, it looks something like this:

1st -> 2nd: 24mph
2nd -> 3rd: 40mph
3rd -> 4th: 67mph
4th -> 5th: 89mph

(I know I'm off a little bit on those, but they're all pretty close...say within a couple mph)

I have a 3.08 rear-end though, so I get alot out of my gears before I gotta shift. Chances are you won't be going as quick as I am when it becomes nessecary for you to shift.

 

[MAKG]

Yup, shift at peak HP. Not the redline.

The redline is where power = losses, well below the peak.

 

[Hahnsb2]

Well as far as the redline goes, should be something like 30MPH in 1st, 50 in 2nd and 75ish in 3rd.

 

[Insanejughead]

I took my truck to 5mph over the above post listing... I wouldn't do that again though.

I can't remember exactly where mine shifts best at, but I just get the "feel" for the torque curve. Once the needle on the speedo starts to not move so fast is when I shift for max acceleration.

Then again, I don't do alot of hard driving.

 

[LearjetMinako]

Ya, shift at peak HP, not redline.

On my 96' 2.3L with slightly oversized tires. Max peak shifts occur every 25mph advance in each gear. 2nd @ 25mph, 3rd @ 50mph, 4th @ 75mph, 5th @ ?. Normally I shift around 3k or less. Or 2nd @ 15 mph, 3rd @ 30 mph, 4th @ 40 mph, 5th @ 45 +.

 

[DeanMoriarty]

Right... I didn't plan on shifting at the red line. I could have worded that better.
I wanted to know that to give me an idea of about how many RPM's I am shifting at... It seems like I'm right about on from what you all are saying. I could probably even run the upper gears out a bit higher.
The problem I have around here is miles of hilly back road, going to miles of hilly highway, so I need to keep it in the lower gear most times to keep it from bogging down. Just wanted to make sure I'm not running the RPM's too high.
I thought about getting a tach... but thinking about it is about as far as I've gotten : /

 

[LearjetMinako]

Ya, shift at peak HP, not redline.

On my 96' 2.3L with slightly oversized tires. Max peak shifts occur every 25mph advance in each gear. 2nd @ 25mph, 3rd @ 50mph, 4th @ 75mph, 5th @ ?. Normally I shift around 3k or less. Or 2nd @ 15 mph, 3rd @ 30 mph, 4th @ 40 mph, 5th @ 45 +.

Forgot to mention that the Max Peak shifts occur @ 5k rpms. 4.8k rpms is max HP for the 96' 2.3L. 6,250 rpms is rev limiter (I never rev that far to truley know).

 

[AllanD]

Actually the ideal shift point while related to redline and to horsepower peak it's much more complicated than that.

Where you want to shift is related to the exact torque at the wheels.

Often you rev PAST the horsepower peak (but never past redline)
because what you are looking for is a tradeoff where the upshift
results in an increase in torque at the wheels Vs simply revving
higher in the lower gear.

Often with real performance engines this is not possible because
the redline happens first so you shift AT the redline.

For this type pf calculation you for all practical purposes IGNORE the horsepower peak and simply look at the torque at any given rpm and calculate for the gear reduction.

IT's ALL about the tradeoff of transmission gearing and bearing in mind that the engine is only apable of producing specific ammounts of torque at different points in it's torque band.



And what determines where an engine should be shifted is
the torque and the transmission gearing ratios.

Upshift too late and you waste time revving for no purpose in the upper gear when you could have been putting more torque into the driveline in the next higher gear, upshift too soon and you push against a taller gear.

It's NOT about "power" it's all about torque.

My current setup in my '87 supercab is the poster child for "wrong gearing"

I'm running a '93 4.0 with Headers (Borla) through a "wide ratio" Mazda trans (basically a 2.9 transmission) in a truck with 4.10 gears.

It revs up WAY too quickly, and the 4.0 is not now nor will it ever be a "Revver" (the basic setup made the more revvy 2.9 very happy) So I'm switching out the wide ratio trans for a "close ratio" (4.0 trans) AND switching to 3.73's. (Highway cruise rpm issues)

 

[DeanMoriarty]

Well, all of that does make sense.
This is why I like asking questions and reading the forums here, there's always a range of answers and information to check out.
You guys rock.

 

[MAKG]

Allan, while it's true that it's not about power, if you scale torque for the gear ratio, you end up with the power peak (torque*rpm).

At least, for a nearly flat torque curve (a design point for highway vehicles).

 

[Totalled]

When it falls on its face and is making more noise than power.. shift.. you're there.