Here's another vote for hoping you try it and report back with results. I am seriously considering one of these for my '06 and my '07 but just haven't talked myself into it quite yet.
If you tow much at all this option would seem to be the way to go over taller tires or changing gears because it retains all the original gearing plus adds more. So when you need the power it's there and when you are empty and can use the double overdrive that is there too.
It also seems that this unit would be able to be taken off and installed on a different truck if the first truck had to go - for the cost of a driveshaft or maybe a driveshaft swap with the new truck if it was the same size.
Just my 2¢

 

I have been seriously wanting to do this as well because I so much highway driving. Not that it means anything, but the newer GM D/A's with the 6 speed only run about 1700 rpm's at 70 mph. Four miles a gallon would save me about $90 a week when I am laid off from plumbing and driving full-time. I might look into it when I go back to work in a few months and am making real money again!

 

4 MPG would mean a break even point under 50k miles.

 

I think it is not unreasonable when the unit is used when it should be ie unloaded and not on a steep grade it will still allow the diesel engine to push the truck. There is a switch that goes in the cab and the unit knows when you go below 20mph or when 4x4 kicks in incase you forget to kick it out when getting off the freeway. It seems good to me....expecially for people with the big gears...they can keep that big towing final drive and still switch back and forth when unloaded.

I know the truck will have no problem pushing it through the air unloaded at 75mph with this engine and the doubleoverdrive unit engaged but I wonder how much fuel it will actually use, that is the $3,000 dollar question. The computer in this truck is liberal with fuel and works in concert with the boost.

Oh and the warranty should go unaffected. They would have to tie a major problem to the gear vendor unit and this company was making overdrives before Ford ever had an inkling in there eye to do it.

It would be nice if there was an economy button from ford to bring the engine back a little when you don't want or need all of the engine.

 

i have heard from first hand experience that the gear vendor has some issues that will make you want to pull your hair out. i am not sure if you have done a search on this site or not but i would caution you to try another overdrive unit. something that does not have all the fancy computer controls.

 

The 2 big names are either Gear Vendors or US Gear. I believe US Gear has a higher capacity rating. From what I've read it sounds like a Ford vs. Chevy argument.

I have no idea which one is the Ford. You might try looking for an authorized service center or dealer from either one of these outfits that's close by. Maybe they can get you in touch with someone local who has done what your thinking of.

 

A Gear Vendor will not void a factory warranty as it is not a power adder modification. GV has contacted the 'big 3' and the results from each are the same. That's not to say that you won't run into dealerships that have jerk service writers or simply a service writer that doesn't understand how it works and will not honor the warranty.

As far as problems with computer controls is concerned. It is true that there are potential problems...the more devices/systems that are added, the greater the chance of an issue. A GV system has the ability to tie into 4x4 systems, exhaust brake systems and also torque converter lock up circuits. However, if you get down to it, a gear vendor could be run off a switched 12v source...nothing more. That would leave the owner in direct control of the unit at speeds of 18 mph and above. Of course in a 4x truck doing it that way leave the chance for an owner to switch to 4x and forget about the difference in ratios from front to rear. Not good. You also run the risk of decerating past 18 while in OD and having residual pressure left in the system, which will leave the clutch engaged. When this happens your truck could roll backwards (even in park!) if you don't use your parking brake....you know, the little pedal on the far left against the kick panel...most people never use it instead choosing to trust a tiny parking pawl in the tranny to hold their rig.

A US gear also has it's issues. That unit is shifted via an electric motor. Internally it is much like a manual transmission...syncro's and all. I have seen/heard many reports of motor failures, synchro problems etc. Think about it. If the motor fails, or syncro's die you'd be potentially stuck between gears, most likely in traffic. The way a GV is built you would have to literally grenade some internals in order for it to leave you stuck. US Gears by nature are also noisey as compaired to a GV.

If you would like to take a look at a GV simply contact your local Camping World and ask if they have a GV cutaway display that you can look at. Same for US Gear, contact a local supplier and see if they have a display model.

On a sub note Gear Vendors have been used in several OEM applications. Some UK delivery vans\trucks were built with them, and they were also OEM in the twin turbo Callaway Corvettes. The design stems from the old Laycock OD's that came standard in a lot of cars 'back in the day'. Volvo for instance. They are one of the reasons Volvo's have the longest life expectancy of any vehicle on the road.

 

Hmmm. GVJosh, and all his posts seem to be related to overdrive issues. Someone's not ready to become a sponsor yet I assume.

So Josh, any comments on the original question in regards to fuel mileage. Any feed back from real world applications with the new trucks?

 

Yeah, in my spare time here at work I peruse truck forums looking for people with GV issues. I'm not a salesman, I am tech support. I'm working on an effective pitch to the 'higher ups' to get the funding to become a vendor/sponsor here and on other truck and hot rod forums. Some sites are pretty expensive though and this could prove a tough sale. Spending several hundred a month on ads in one forum may not produce sufficent sales to offset the costs. I'm trying though, I promise!

As for the original poster and his fuel economy, yes, he will realize MPG increases. However it is directly related to HOW the driver drives. The aerodynamic drag at 75 is subtantially higher than at 65. If your driving in a head wind at 75 up a 5% grade towing your 5th wheel your obviously not going to get 20% better fuell economy. Now if your empty cruising though town on the highway at 70 your likely going to get around 20%. Real world reports are 2-8 mpg increases...and that's across the board on GMC/Ford and Dodge trucks and everything from 30000 lb combined weight rigs to empty daily drivers. The lower numbers being the guys who flog their trucks towing 5th wheelers loaded with cattle and are pretty much floored most of the time.

 

Can you explain the failure modes on a GV better? Short of a complete self destruct with internal parts flying everywhere, what happens when there is a failure? Are you just defaulted back to the original gear set up? Is there any difference between manual vs. auto tranny's in failure types? How many things can go wrong that would leave you stuck on the side of the road? Any comment on why the other guy has a higher GVW rating on his unit?

Many of us are interested in an overdrive unit. If you have access to any customer records maybe you could encourage them to join up here so we can pick their brains also. Eliminating the "unknown" could help GV sell more units.

 

Could this also improve the acceleration?

 

If you know what your doing, yes. It will allow you to keep the rpm's in the optimum range by limiting the amount of RPM drop during shifts, but you will have twice as many shifts.

Big help in acceleration while pulling a trailer by minimizing RPM drop. If your using it in a race mode then you need to be coordinated.

 

Thats what I was assuming. I figured since the gears will be spaced closer and there will be less of an rpm drop at each shift that it would be a bit quicker, but like you said there will also be twice as many shifts.

 

First, there are two 'systems' to a GV unit. Mechanical and electrical.
The mechanical system consists of the GV unit it's self. Internally there is a pump that draws the oil from the sump and produces 650psi of pressure. This pressure is used to operate the cone clutch which when engaged operates the planetary gears and gives you the .78 overdrive. When pump pressure is removed from the clutch it disengages (via spring pressure) and returns to a 1/1 ratio.
The electrical system consisits of a few basic components:
Control box - Self explanitory
Dash switch - In maunal vehicals it an on/off switch with a green light indicator. In Auto vehicles it's a manual/autodrive switch with red and green light status indicators.
Manual control switch - In manual applications this is usually some sort of switch attached to the gear shifter. In auto's it's generally a footswitch...just like the old headlight dimmer switch's. This switch is what you use manually operate the GV...splitting gears for instance
Signal gerenator - The control box needs to see accurate vehicle speed. We can do this a variety of ways. We can use a signal gen driven by a speedo cable attached to the GV. Some applications (like 90's & '00 ^ GM's) require us to tap into the signal generated by factory components.
Solinoid - Attached to the GV. When activated it allows the above mentioned pump pressure through to the pistons that operate the clutch.

Other than that there is the wiring for all these components, as well as the wiring for peripherals like 4x4 lock out, torque converter interupt, and other lock outs like exhaust brakes.

Most failures are electrical in nature. A solinoid dies, something kills the control box, occasionally a switch will go bad, a connection gets funky. As far as problems with the GV overdrive it's self the most common failure...and it's not really a failure...is a worn out clutch. You'll feel it start to slip when your towing. The most common breakage is the one way roller clutch (sprag cam) when someone is backing a heavy load. Last one I saw a guy was backing his 24' 5th wheel and backed a wheel into a rock. Instead of figuring out WHY the truck stopped moving he gassed it to get over the obstuction. BANG! The GV's weakest point is in reverse. It's simply not designed to push those type of loads in reverse. For guys with 4x4's we recommend putting it in 4x when backing under those conditions. In that guys case he still had forward gears, but could not reverse in 2wd.

Short of what you said...a massive explosion is internals or a shaft breakage, your still going to have the ability to drive the truck in normal factory forward gears. I've seen just one case where a guy was stuck. It was an old unit, before we nitrided the shafts, and he broke a shaft. Trucks, motorhomes and high HP cars are getting nitrided shafts now. 99.9% of the time your going to be able to use the truck in factory gears when there is an issue with the system.

As far as higher GVW on another guys...not sure what your saying. Are you asaking about US gears unit?

 

Thank you for your input here. I like the GV unit but the price is steep....I am still thinking about it.