http://www.gearvendors.com/ag4s.html
I have the 99 with tall gears. Oversized tires from previous owner. I often reflect on wether I want to start modding my truck and sometimes want some more performance.

With gas prices on the rise it is a consideration also. I own a 4X4 with 4:10 gears and was looking at this gear vendor unit to get me back up to cruising speeds without over reving. The main issue was standard cab short driveline and drivshaft angles in addition to changing the rear without being able to do the same with the front....

Well, now I am thinking that I might be able to use this device as an underdrive on the L. Since it is two wheel drive. It would be nice to compliment my flip chip moods with another switch to lower my gear ratio from 3:54 down lower for hole shots and fun but still be able to flip back to high gears for better fuel economy, less engine wear and noise when cruising or doing the comute.
http://www.gearvendors.com/facts.html
Can someone figure out what the ratio would be with a few different stock gear combinations? I never did math well.

In vehicles with automatic transmissions the unit is intended to shift at any throttle position including full throttle and delivers a crisp responsive shift. Shift it as much as you like . . . the internally activated common vertex clutch is designed to last 250,000 miles. Vehicles with manual transmissions also benefit from the constant mesh planetary gear design as both in-shifts and out-shifts are as simple as depressing the vehicles clutch pedal and pushing a button. No syncros to wear out, no grinding gears or misshifts possible. The systems sophisticated planetary design has very low friction which means not only will a GEAR VENDORS last longer, but it's quieter and has less power loss (less than 1hp per 400hp) than any other auxiliary transmission. All GEAR VENDORS UNDER/OVERDRIVES™ offer a .78 to 1 (22%) overdrive ratio, designed to be the ultimate gear splitting and overdrive ratio for today's RV's. Anything less than 22% would be less effective at slowing RPMs while cruising in overdrive . . . anything more than 22% wouldn't be effective as a gear splitter when you need power to climb hills or to pass slower traffic. Performance through proper gearing is the cornerstone of GEAR VENDORS UNDER/OVERDRIVE™.

 

3.54 X 22% =.7788 and subtract that from the 3.54???? 2.77

or do you add getting 4.31

going from 3.54 to 4.31 ratio at a flip of the switch would be awsome seat of the pants G force.

If thats right

3.54/4.31

3.73/4.53

4.10/ 5.0

Is this right?

 

Did you check the prices? with the new driveshaft that thing is like $3k....until gas costs about $100 a gallon i can't see that thing being benficial from a gas mileage stand point. I think you'd be better off just switching to the gears you want and getting worse mileage.

 

I understand that, but I see a lot of folks spending a lot more money to improve performance and the truck just sits in the garage most of the time.

Your point is well taken cost wise.
What I am looking for is a way to have stock reliability and longevity and still have some holeshot performance and do some tire spinning light to light.

IMHO low gears are the best way to get there. Most of the folks getting low numbers at the track are going to lower gears or smaller tires or both. (not that I will ever race)

That works well at the track but is not very fun on the highway as a daily driver. Cruising at 60 MPH with your engine taching at 3kRPM and your cooling fan kicking on and off is not my idea of fun.

So I was just thinking that as a underdrive you could have the best of both worlds wether you have a stock truck or not. Best of all it is at the flick of a switch.

Try as I may I am scratching the heck out my front end plastic on these crummy driveways around town. I am going to go to a 285/55/18 tire which is 2" taller and will ride more comfortable but it will hurt my low end performance.

When I was a kid we always went to the junk yard looking for a 4:10 or 4:56 posi rear end pumpkin to throw in our cars. It made a hudge difference alone by itself. I remember helping a buddy with his 62 Vette change it for his cross country trip to visit an uncle. Two weeks later we pulled out the 3:07 or waterver it was and put back in his 5:13. We had it down to just a couple of hours and a Sixpack. I am to old and tired (Lazy) for that now. I will pay for the ease of toggle switch if it does what I want.

I sent in a e-mail to them for advice so I will post the results on Monday sometime I guess.

Still looking for conformation on my ratio's though.

If someone will post a link to our tranny ratio's I have a gear caculator that I can make some comparision graphs.
Any help there would be appreciated.

I hate the way I over analize every little decision in my life.
Thanks guys
Greg

 

You are going in the wrong direction. The GV unit is an OVERdrive, which means that it LOWERS the effective final drive ratio, which in turn lowers the engine RPMs for any given speed.

A 3.54 final drive X 78% GV overdrive = 2.76 effective final drive.

To find the ratio for each gear, you have to multiply the gear ratio X final drive X GV reduction (.78).

Bottom line: to take advantage of the GV, it would be best to install a higher numerical final drive such as a 4.10, which then becomes a 3.20 when the GV is engaged.

I don't think that it is a waste of money at all. Although the drag racers mostly report that 4.10s only cause you to lose traction worse, for all-around use, it may provide a more subjectively satisfying seat-of-the-pants driving experience. The GV, 4.10s, and a centrifugal. Hmmmmm....

 

Thanks Tim,
I am not sure why they call it and over/underdrive. I was hoping to go the other direction to get to the 4:31 example.

I still think it is the best of both worlds. Gives you seat of the pants thrill, Might not effect warranty, can change it back to stock and by changing the tailpeace adapter.
It will fit on different vehicles to. I don't think it does anything but bolt up to the back of your tranny. You would however have to shorten your driveshaft. Since I have the steel one anyway I could save that and upgrade to a shorter aluminum one.

Here is another recent case in point from the slick X post
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im still stuck with the 3.55 gears..... how do you like those 4.10?? i was considering doing that.... any noticable gas milage??? how about highway driving???



Slick X
Member

Registered: Dec 1999
Location: MS
Posts: 97
milleage was slightly worse, if I did it again I would do 4.56s

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Low gears are definitly the most bang for the buck but it takes away the streetability and practicality.

Still waiting for some Tranny ratio numbers for 1st threw OD

 

EZGZ, I don't think you'll see an increase in gas milage by going to a taller gear. I swapped to 285/60-18s thinking that the decreased rpm on the highway would increase my gas milage. I now have an effective 3.26 rear end ratio, but it didn't have the effect I wanted. I get the same mileage on the highway, and less around town.

I think the key to better mileage on the highway is keeping the boost guage in the vacuum range...the deeper the better. I had my boost actuator adjusted where I could cruise at 80-85 mph with the boost guage needle all the way down. Since the tire change, unless I'm on a completely flat road, the increased gearing makes it very difficult to stay out of the boost range, even at 70 mph.

Ford knew what they were doing when they went to the 3.73s, and I think the 3.55s are the maximum you can use for gas mileage. With a transmission OD ratio of .71, that gives a final drive ratio of 2.52, which is pretty tall for a truck.

On the other hand, swapping to 4.56s with the gearvendor OD will put you back to 3.55s (4.56x.78=3.5568), and that should definately wake up your throttle response.

 

if your doing it for performance purposes then go for it but simply put, never ever ever buy mods for gas milage alone. I've done the calculation many times and it doesn't pay for itself until far down the road mostly and even then, it's a slow savings after that. This thing looks like it costs about 3k all said and done, so lets do some math.

lets for simplicities sake say its just 3k all finished.
lets say you get 12 mpg now on average, they of course don't give specfic milage gains, but on the bottom there they say something which kinda implies 25% less rotations so lets just say it gets you 3 extra mpgs, hell lets make it 4.

lets just say gas is 2 bucks a gallon (2.50 out here but your in colorado i don't think it's that bad yet) and say 12k a year in driving.

Intial cost is 12000 miles/12 mpg= 1000 gallons x 2 dollars= 2000 dollars a year in gas cost.

after said mod 12000 miles/16 mpg=750 x 2 dollars = 1500 dollars a year.

So overall your going to take 6 years to just break even, and thats under fairly ideal conditions. Now 500 bucks a year after that isn't all too bad, i'll admit, but that was a pretty big investment for get that, and after 6 years are you even going to be driving the truck that much, are you going to even own it?

I say you just regear it and screw the milage but it's up to you.

 

I agree that gas mileage is a nonstarter for the average driver.

But the performance aspect is interesting. In addition to potentially quicker acceleration, those who run open road race REALLY fast could bypass the gear-related top speed limit (assuming that you have enough HP to get there).

 

All well thought out points and as usuall very informative.

Thanks for doing the math on the payback. That puts it in a new light also.

Another brain fart I can put on the back burner!

Thanks guys! With my extra unspent money (credit)
Let me buy a virtual Round for the house

I will post the sales hype that I get on my inquirey with GV
I bet they will have all kinds of hype that will be interesting.