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Gear Vendors Save Gas or Diesel Fuel Extend Mileage using NV4500 and the ZF 6 Speeds, Extend Engine Life, Start Saving Money Today!

Does your Chevrolet or GMC need 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, see application guide . Our Gear Vendor overdrive for Chevrolet GMC are available for manual transmissions using:  NV4500 and the ZF 6 Speed. Our Chevrolet GMC overdrive transmission provides 500 to 600 less RPM's plus 20% increase in fuel economy. You'll need an auxiliary overdrive transmission capable of gear splitting behind your transmission. The toughest built best performing auxiliary overdrive transmission you can buy is the Gear Vendor overdrive from Drivetrain Specialist.

See How It Works, Guaranteed Amazing Performance for Your Chevrolet or GMC

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 the Gear Vendors and so rpm is sustained - higher torque and rpm on shift = more Horsepower. When shifted into overdrive final gear reducing both rpm and torque to reduce the manufacture of HP when steady cruising to improve fuel mileage and decreases wear on your engine. Two-year warranty rated at 30,000 pounds applications for Chevrolet and GMC, most beneficial when used in commuters, tow vehicles, 5th wheels and Motor homes. Our overdrive kits are very complete and are designed for your specific vehicle, detailed installation instructions are included in kit, and installation is also available. Related to fuel economy, performance, and emissions — Gear Vendors overdrive units include state of the art electronics circuits that keep your vehicle in the optimum performing gear. Whether you are driving a older non-computer controlled vehicle or a late model with all the latest emissions computers our electronics provide the interface to ensure maximum performance and correct rpm without lugging or over reving in the wrong gear. The OE factory programming remains intact and our processor just makes it aware of the actual ratio 1,000 of times per second. In older vacuum or throttle linkage transmissions the stock governor on the output shaft instantly slows down the moment the overdrive shifts and so automatically moves the shift point in any overdrive gear up by the correct 28.6%. So both electronic and non-electronic automatic transmissions gain a group of features including a passing gear or climbing gear that is automatically available without driver intervention and is at the split between 2nd and 3rd where you really want it. Need more information on how to save gas or diesel fuel?

Gear Vendor overdrive Kits are Complete with Adapters

Gear Vendors overdrive Kits are Complete with Adapters Our Gear Vendorss overdrives are supplies with specific adaptation kits for each model of transmission model, the kits are completed. By supplying specific extension housings to each model/brand transfer case Gear Vendors is able to have a better product with gvyoutubesema2008.jpg increased engineering benefit to the final installation. Fact is, when you are in 4X4 there is very little desire to use Gear Splitting and overdrive unless you are racing (and we do make the in-between kit for that purpose), it's 2wd where the benefits of overdrive and additional gears are most needed, see YOUTUBE video for more information.  All our kits bolt directly to the rear of the transmission, you can manually control the unit or we suggest you flip switch when leaving city limits sign and turn it off when you get to next city limit sign. No additional cross members are required and you retain the factory ground clearance instead of moving the transfer case rearward which puts it at or nearer the middle of the wheelbase where ground clearance is most critical. You get all the benefits of the Gear Splitting performance and overdrive economy (see your appropriate transmission under GM/Dodge/Ford 2wd) and the best auxiliary transmission you can buy.


Free Technical Support, Get Expert advice about your vehicle's performance with our Gear Vendorsss Overdrive. Call toll free at 800-216-1632. More fuel milage 20%, 600 RPM reduction in Engine RPM means longer life and you save Money!

You get all the benefits of the GearSplitting performance and overdrive economy (see your appropriate transmission under GM/Dodge/Ford 2wd) and the best auxiliary transmission you can buy. Give our overdrive expert a call toll free 800-2161632 he can answer your questions and help you pick correct model for you application, and get free telephone support during installation when you purchase from    Free shipping within the continental United States only.

  • You need quality.
  • You'll want reliability.
  • You want performance 22% Overdrive.
  • You want better mileage 20% more fuel economy!

YOU WANT A Gear Vendors


Bolt on Performance and Economy! 


Overdrive for Chevrolet GM 6 Speed Manual Transmissions

  • Save Fuel
  • Extend Engine Life
  • Save Money
  • 30,000 lbs Capability



Click image to enlarge.

For detailed information on General Motors 5 and 6 speed manual transmission with our overdrive unit select from one of the following:

GM NV4500 5 Speed Manual Final Drive Ratio

GM 5 & 6 Speed Manual Application Chart & Pricing

Look at the Final Drive Ratio charts and notice the great benefit in gear splitting with the Gear Vendorss. When you are climbing grades you will have a gear between 2nd/3rd and 3rd/4th that is ideal for keeping the engine in the power and the torque multiplication up. Look at the horsepower and torque curves and noticethat by keeping the engine in the power band you will gain 50+ horse power and 60+lb. ft. of torque without any modifications to the engine.

The more heavily you are loaded the more you need our overdrive unit and when you are heavy you would do best by not using 5th but instead use 4th+Gear Vendors (4th over). This will keep your transmission temperature as much as 100 degrees cooler (extending transmission life) and puts the stress on the Gear Vendorss planetary gearing which is much stronger than your 5th gear.

When you are running empty, 5th-over (double overdrive) will net you better fuel mileage and far less engine wear at today’s 75mph speed limits. Not only is the engine turning slower but so are all of the engine driven accessories and this cuts down on parasitic losses (turning an a/c compressor or alternator slower greatly reduces the load on the engine).

For the empty truck which never tows and is never driven above 55-60mph the stock transmission is good, but for everyone else the extra gears will give great performance gains that will actually pay for them selves many times over the life of the vehicle. Even the resale value of your truck will improve by more then the cost of the Gear Vendorss because you will be able to point out that the engine has seen better care and effectively far less miles than other used trucks.

If you tow or run at speeds above 70mph there is just no good reason not to have a Gear Vendorss UNDER/OVERDRIVE.  

Find you transmission and rear gear multipliers below. The Final Drive Ratio shows you how many times the engine turns for one complete turn of the tires. This Final Drive number is also your torque multiplier when in that gear.Gear Vendors reputation for being to best is because of its sophisticated planetary construction. This means Gear Vendor is the only auxiliary intended as a gear splitter behind automatics and the nicest to work behind both automatics and manuals. You are able to shift half gears that keep the engine in the power. Any auxiliary that requires you to let off of the accelerator or is not intended to shift frequently is not going to give you this performance.

Final Drive Ratio NV4500 5-SPEED Manual Transmission

Axle Ratio


Rear End Ratio 






Transmission Ratio

Final Drive Ratio











































5th  O/D






Double Over






Please Click on Part Number to buy it online 

Chevrolet/GMC Application Guide 2 Wheel Drive 5 and 6 Speed Manual
Part Number Transmission Comments Description
3D4500C Manual 5-Speed NV4500 Replaces tailhousing. 94-97 3/4 and 1 ton trucks with mechanically driven electric speedometer. 
3D4500E Manual 5-Speed NV4500 Replaces tailhousing. 98-02 3/4 and 1 ton trucks with mechanically driven electric speedometer. 
3D4501C Manual 5-Speed NV4500 Elec Speedo Uses GM 4x4 adapter (included). 93 and newer 3/4 and 1 ton trucks with electric speedo.
3D5600C Manual 6-Speed NV5600 Replaces factory 2-Wheel Drive tailhousing with Dodge 4x4 tailhousing. 99-2004 3/4 and 1 ton pickups. Includes factory 4x4 tailhousing.
3D5601C Manual 6-Speed G56 ZF Nose Direct Mount Kit. 2005 and Newer 3/4 and 1 ton pickups - Bolts directly to tranmsission. 

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.