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Discussion Starter · #1 ·
Ok, I've been trying to do some research, and I cannot seem to find any specs for my PRO-4X transfer case, and trans gearing.

What makes me curious, is that I kinda did something semi-stupid the other day, just to see what the results would be...

I pulled out of work, and came to a red light.
A little red rice-burner civic pulled up to my right, obviously wanting to race me, and at the same time, a newer 370Z pulled up on my left (3 lanes on each side of the road, with red lights at about every 1/8 of a mile or less, on the way to the freeway). I said what the heck, threw it in neutral, and dropped it to 4-LOW, then back to drive. The light turned green, and both the Z and the Civic punched it, so likewise, I did too, giving them probably 1/2 a second head start.
To my surprise, I pulled past both of them as if they were standing still, then when I had about 5-6 car lengths between me and them, I looked down at my gauges, to see that I was at 5700 RPM, in 5th gear, doing about 62mph!
I kicked it into neutral, coasted to the next light, then stopped and put it back in 2WD, only to see both guys catch up to me, give me dirty looks, and then go their separate ways.

I haven't done it since. I've been tempted to, to try & time it and see exactly what the 0-60 is, but I was curious to see some specs on exactly what the gear ratios are for each gear, and the difference between the HI/LO range on the transfer case, to formulate just how I got those results.
 

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Driving 60mph on dry pavement in 4Lo is... Well... DON'T DO THAT! Jesus Christ.
 

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Discussion Starter · #3 ·
Driving 60mph on dry pavement in 4Lo is... Well... DON'T DO THAT! Jesus Christ.
Haha! Yeah, you'd think a master tech, and former Nissan dealer tech, would know better, lol!
But I couldn't resist, and it was pretty exhilarating!

I know all too well, if anything goes wrong, I'll be the one to fix it, and I'll be the one forking out the money for the parts.
It's not something I planned to do, just to show off, it was more like a "hmmm, I wonder just what this thing will do?", kinda like that once in a lifetime, wild Ferrari test drive.

Now in the aftermath, I'm just trying to figure out the gearing that put me out there so far in front of those other two (considerably faster) cars...
 

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Discussion Starter · #5 ·
That's exactly what I was looking for! Thank you Justwork!
Oh, and that crawl ratio is referring to the first gear on the manual transmission Pro-4X, when combined with the 4LO, and rear diff gearing. I found that, but none of the other details, nor that nice table chart you included, thank you!!
 

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Discussion Starter · #6 ·
I know the formula is wrong, but just for demonstrational purposes, if I were getting 265HP to the rear wheels, then by going into 4-LO, I put 695HP to all four wheels!

But, that's just for demonstrational purposes, so before anyone says anything, when you equate the block horse power into that formula, you still have the friction, individual gear paths, and the various gear ratios of everything from the transmission, to the front and rear differentials, to contend with...
All of which will change the way that horse power is applied, and therefore the amount of horsepower you see at the wheels will almost always be less than what the engine itself is capable of.

Regardless of the correct formula or equation, that's a hell of a lot to subject the stock front and rear axles to!
 

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Good way to smoke the spider gears in the R180

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Rear wheel horsepower on a stock Frontier VQ40DE-equipped truck is about 215 HP peak. CAI and performance exhaust might net you a couple more. I'm not sure where you are getting your numbers from.
 

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Discussion Starter · #9 ·
I didn't say it was exact, and I eluded to the fact the the block horsepower will always be a little more than the wheel horsepower.
Aside from that, if the standard gearing for the transfer case is 1:1, then by my math, the wheel horsepower in 2H or 4H, will be roughly 207-213.

Take that number, and multiply it by the 4L ratio of 2.63:1, and from there, we can guesstimate that the WHP in 4L is roughly 545 to 560!

Yes, these are only approximations, and hypothetical, not real-world factual.

But, 350+ HP on anything less than a Ford 9" or Dana 60, is asking for trouble!
And also something I have personal experience with, after pushing my Titan to 340HP, and shattering 3 pinion gears...

Not something I'll ever do again, now that I finally got the specs I was looking for.

But Dam! It sure was fun! LOL
 

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When a dyno reports rwhp doesn't it adjusted for gearing? The 215 above is true when the gears are taken out of the equation. In reality you are getting around 560 actual hp. Maybe I don't understand how it works.
 

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Neither of you understand how it works. The gears of the transmission, transfer case and differential only effect how the power from the engine is transferred to the wheels. It's a compromise between force and speed, determined by the gearing and engine's power. When taking off from a stop, we choose a lower gear, which gives us more force, but sacrifices speed. This is a good thing, because if we tried to go from a dead stop to 55 MPH in a second, we'd either stall the engine or break something in the driveline. Once we get moving, we have more speed (albeit, limited by the selected gear) but less force, therefore requiring a higher gear if we want to go faster. So, we shift to a higher gear which again uses more force, initially, but starts with a low speed for that gear. Of course, this cycle repeats itself until we run out of gears and get to top speed (or, our desired speed, in which we start decreasing throttle and engine power). "Force" is not the same thing as "power," rather, it is a determining component of it. Power=force times speed. To determine "horsepower," we take the pounds of force and multiply it by the speed in MPH and divide the total by a conversion factory of 375. To put this in layman's terms, a stock or lightly modified VQ40DE-powered truck is only going put out around 215 (give or take a few) peak, rear wheel horsepower and the only way to increase that number is to increase the power output of the engine, not by changing the gearing.
Dynos do not "adjust for gearing." The measure the actual horsepower and torque at the rear wheels.
 
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Discussion Starter · #12 ·
You are absolutely correct, and I was going about trying to figure this out with faulty formulas.

The reduced gearing in 4Low allowed the engine to apply more torque to the wheels, propelling me thru all the gears, and past the other vehicles, more rapidly than the typical gearing in their vehicles.
 

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There has to be gear calculations to get rwhp. It just doesn't make sense to me that there isn't unless there is a perfect 1:1 ratio. Following is a link and a quote of the type of stuff I am talking about. I'm not pretending to know a lot about dyno's but I just don't believe it is as simple as just measuring the torque at the rear wheel because gearing does effect that.


http://www.corvetteforum.com/forums...-end-gear-ratio-effect-your-dyno-numbers.html

Following taken from the above link.

"Any rear wheel dyno will measure engine RPM and rear wheel RPM and can compute overall gear ratio. The dyno will not know if the multipication is coming from the transmission or the rear axle unless there is an operator input to the program for that data. Reguardless, any gear multipication up or down will generate loss. The more the multipication, the greater the loss.
A dyno test run in first gear (Z06) multipies 3.42*2.97=10.16. 400 lb/ft of engine torque would put close to 4000lb/ft to the rear wheels. The dyno would measure the ratio between engine and wheel speeds and divide the measured torque by the computed ratio. The frictional losses of turn the gears would show up and the final computed and adjusted torque would be lower than a like run in fourth."



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You are absolutely correct, and I was going about trying to figure this out with faulty formulas.

The reduced gearing in 4Low allowed the engine to apply more torque to the wheels, propelling me thru all the gears, and past the other vehicles, more rapidly than the typical gearing in their vehicles.


I don't get it. The amount of parasite drag would be huge and I'm honestly surprised you didn't blow up your front diff, cvs, and actually even your engine. I can't see any gains in off the line acceleration that wouldn't be lost in about 200feet.
 

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You can use gear calculations to determine rear wheel horsepower but you need other inputs. Also, rear wheel horsepower, which is what we were original talking about, is very different than torque and different formulas apply. My point was that the formula Mob was using was incorrect and that he did not have anywhere near 540 horsepower at the rear wheels. If that were the case, none of us would have any money because we'd be paying speeding tickets and replacing the tires everyday from burnouts!
There are a number of "guestimators" on the web that will ballpark wheel horsepower (see link below for an example) and such things with limited input. They work pretty good to get us close to the answers we're looking for without having to run a complicated Albert Einstein equation to get more accurate results or actually putting a vehicle on a dyno, which wouldn't be important unless one is trying to squeeze out every bit of performance for racing or other such purposes.

Wheel Horsepower to Crankshaft Horsepower Guestimator
 

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I'm just surprised you could take a 370 in any way whatsoever. I just can't seem to shift the gears in my fronty very fast. That shifter is not really set up for quick shifts, not like my hardbody is, and certainly not as quick to shift through your gears in a 370. The whole LO range setting aside, I'm just astounded you were able to outshift that 370.
 

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Torque is a descriptive term for a measure of a twisting force. As we are used to seeing, torque is measured in pound feet - the twisting force required to move an amount of weight a certain angular distance (typically at the crankshaft).

Horsepower is the speed at which torque is applied. It is a calculated measure typically using torque and engine RPM. This is why torque and horsepower curves always cross at 5,250 RPM.

Transmission, transfer case, differential gearing can multiply torque, but divide horsepower. Of course this is at the wheel, torque at the crank remains unchanged.

Gearing absolutely is taken into account on a chassis dyno - which measure torque and calculate horsepower at engine RPM, not tire RPM.
 
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