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Gear-Splitting Performance and Overdrive Economy for RV's, Trucks, Muscle Cars, Hot Rods, and Racing. We offer the gearvendorcutaway_large.jpgfinest quality auxiliary overdrives. Our units are the ultimate in horsepower handling and performance. In this section you will find general information on performance improvement and saving vehicle life by running engine at lower RPM's. Follow the links below and find the application guide for your vehicle. Or you can email or call us at 800-216-1632 for free technical support!

Whether you are trying to move a couple tons up a steep incline in your work truck or cruising in your motor home - the fastest way is with the right gearing with one of our gear vendor overdrive units. Add the benefits of our final overdrive ratio to reduce engine rpm and increase fuel mileage by typically 20-28%, bolt on horsepower and economy for your your car or truck. With fuel costs overdrive can pay for itself in mileage and engine wear reductions.

View our chart below to find the right overdrive unit for your vehicle.

Torque (times) RPM (divided by 5252) = Horsepower (this can be expressed) Tq X RPM / 5252 = HP. Our Gear Vendors Overdrive is one of a few products that can work both sides of this equation for real performance gains as well as consistent fuel consumptiongvinstall_large.jpg reductions. Gears are multipliers of torque and our Ratio Splitting capability allows you to shift to a gear with more mechanical advantage than the next stock gear in automatic transmissions and wide ratio manuals. This also means engine rpm drops about half what it did without this overdrive and so rpm is sustained - higher torque and rpm on shift = more HP. And then shift to an overdrive final and reduce both rpm and torque to reduce the manufacture of HP when steady cruising to improve fuel mileage and decrease wear on the engine and engine driven accessories. All these benefits from Gear Vendors ratio splitting performance, at the same time this ratio splitting makes less work for the main transmission in the vehicle to then advance to the next gear (less ratio change) and thus the main transmission itself becomes more reliable. The unit ships in kit format, lots of detailed instructions, parts and in most case all mounts are supplied, typically installation including electronics takes about 8 hours for a skilled installer. Auxiliary Overdrive Units for Pickups and RV's twice the forward gear ratios.


Installed Gear Vendor for 20% better cruising mileage.


Installed Gear Vendor for more Power moving landscape equipment trailer.


Gear Vendor More Power More Mileage for longhauls.


You want more power to climb hills or tow with heavy loads, plus at the touch of a button taller gearing for cruising down the highway with the lower engine RPM's and improved fuel mileage. You'll need an auxiliary overdrive transmission capable of gear splitting. The toughest built best performing auxiliary transmission you can buy is the overdrive from Drivetrain Specialist. 22% overdrive 20% fuel savings, two year warranty rated at 30,000 pounds applications for Chevrolet, GMC, Dodge & Ford AOD transmissions and most beneficial when used in motorhomes. Our overdrive kits are very complete and are designed for your specific vehicle, detailed installation instructions are included in kit, installation is also available. Select your vehicle from the following table to see detailed information on improving your vehicles performance and saving money today!


This overdrive gives your vehicle up to twice the forward gear ratios for unparalleled performance.

Most auxiliary transmissions are just dual ranges (put them in low for towing, high for running empty) but you still have the big gaps from one gear to the next that rob performance. You could actually go slower than you do now. The UNDER/OVERDRIVE™ is built for giving you a progression of gears with 1/2 the drop in rpm of the stock vehicle so that you stay in the power with close ratio performance. More power than just an underdrive or overdrive and just one of the reasons the GEAR VENDORS UNDER/OVERDRIVE™ is the most industry awarded transmission you can> Electronic Features


Our overdrive is electronically superior. In older vehicles without computers our simple plug in electronics still provide many features such as AUTODRIVE™ which make your car or truck perform just like it came factory with the overdrive. Those older 3-speed automatics also adjust their shift points automatically because we slow down the governor on the trans whenever the overdrive is on. For you this means the vehicle will not lug and will shift down to a passing gear that is really useful instead of just screaming the engine. In today's computer controlled vehicles we communicate directly with the vehicle so that shift points recognize when you are using the GEAR VENDORS and adjust performance automatically. In either vehicle you can put the electronics in auto and enjoy several features or flip a switch to manual and control everything about the gearing yourself. Take advantage of our 27 years of product development.

YOU'LL NEED QUALITYmotorhome_towingvehicle_lar.jpg

Each Overdrive auxiliary transmission represents the combined effort and technology of Gear Vendors, Inc. (the largest producer of overdrives in the world). The very finest in manufacturing, assembly, and R&D facilities are available. Our customers ride with confidence knowing that we offer the only auxiliary transmission available that is approved and used by new car and motor home manufacturers. Component quality is unsurpassed, Sheffield steel planetary gear set, 4500 ft. lb. roller clutch, forged ring gear assembly, common vertex (cone) full throttle shift clutch.


No matter how much enjoyment you derive from the improved performance of gear splitting on hills and overdrive when cruising, if your auxiliary transmission leaves you stranded in the middle of the highway, you'll wish you never made the purchase. Gear Vendors current "P"-Type UNDER/OVERDRIVE™ is the toughest rated product in the industry. Guaranteed to 30,000 lbs. GCVW, the unit relies on a mechanical lockup roller clutch (Sprague) just like automatic transmissions do to handle the extreme torque peaks of initial take off and change of direction from reverse to drive. It is a completely self contained system with its own integral pump and pressurized lubrication, (features not found in any other auxiliary transmissions). Ask these questions of any other auxiliary transmission manufacturer:

  1. Can the unit get stuck in neutral?
  2. What if the unit loses all its fluid (leak)?
  3. Can I shift the unit under any throttle condition (including full throttle)?
  4. If a major problem occurs, can I simply shut it off and continue driving?

We know the RVer wants a gear splitting/overdrive product that works as well as the rest of his vehicle and can never leave him stranded, period! Price is secondary, Reliability First.


Power is certainly the No. 1 reason more people choose the Gear Vendors overdrive. There is no other auxiliary transmission available which can split gears as effectively.

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 mis-shifts 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 overdrive 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 RPM's 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 overdrive.


There are many devices advertised as remedies for poor gas mileage. Fact is, anyone who tells you how much you are going to gain is just trying to sell you something. Every vehicle represents many different situations, different drivers, different conditions of tuning, different climates and altitudes. The Gear Vendor overdrive is not some magic pill, but twice the number of forward gears for combating all these different conditions.

Every time you shift there are such big changes in transmission ratios that your engine RPM's fall completely out of the power range. You need that half gear between each of your current gears which will not only keep the engine making power but improve its useful life and reliability. You'll no longer be overreving the engine in too low a gear or lugging it in too tall a gear. Plus out of the same device get a gear that lets the engine slow down without slowing down the vehicle which not only can save you a lot of fuel, but greatly reduce engine wear. Imagine the same engine work (RPMs) that currently take you 15.56 miles - can take you 20 miles in overdrive (that's a lot less wear) not to mention the fuel savings and longer range. There is a lot less engine noise in overdrive also. We have included a frequently ask questions section that may answer some of your questions, don't see answers you need, just give us a call we will be happy to review your application with you. The following links provide specific application information, performance data that you can expect and the price data for your specific vehicle.


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