Gear Vendors Save Gas or Diesel Fuel Extend Chevrolet or GMC 700R4, 4l60E and 4L80E Mileage, 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.  These Chevrolet GMC overdrive are available for 4 speed automatic transmissions in 1988 and newer muscle cars and street rods, half ton, 3/4 and 1 ton pickups as well as  Chevrolet, Buick, Oldsmobile and Pontiac cars.  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 700R4, 4l60E and 4L80E. The toughest built best performing auxiliary overdrive transmission you can buy is the Gear Vendor overdrive from

See How It Works, Guaranteed Amazing Performance for Your Vehicle

How it works, 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 Gear Vendors Overdrive for Chevy & GM 4L60E Transmission 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's Complete Kits Ensure a Smooth Installation for You

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 VendorsS is able to have a better product with See how our Auxiliary Overdrive Unit adds 20% more fuel economy. increased engineering benefit to the final installation. Fact is, when you are in 4X4 there is very little desire to use GearSplitting 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 crossmembers 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.  free_shipping.jpg

Free Technical Support, Get Expert advice about your vehicle's performance with our Gear Vendorss 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.

Overdrive Units, GM 4 Speed Automatic Transmissions

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

YOU WANT A Gear Vendors


Bolt on Performance! 


Gear Vendors overdrive 700R4, 4l60E and 4L80E GM 4speed auto transmission

  • Save Fuel 20%
  • Extend Engine Life
  • Save Money
  • 30,000 lbs Capability
  • 2 year factory warranty.
boltonperformance.jpg Quality professional kits are complete, allowing you to install in about 8 hour, including electronics.

 For detailed information on General Motors 4 speed automatic transmission with our overdrive unit select from one of the following:

GM 4 Speed Automatic Truck/Motorhome   GM 4 Speed 700R Automatic Final Drive Ratio
GM 4 Speed Automatic Performance Car/Street Rod   GM 4 Speed Automatic Application Chart & Pricing


GM 4 SpeedAutomatic Truck/Motorhome

There are two basic GM 4-Speed automatics: The light duty700R4/4L60E found mainly in half ton or lower applications, and the heavy duty 4L80Ein the heavier applications.


700R4/4L60E’s have a low 3.06 first gear which is good for initial take off but this makes the transmission have the widest ratio changes of all popular makes. The intention or the designers was best possible EPA ratings,not performance. The Gear Vendorss will give you Gear Splitting to those wide ratios with a rear between each or them for the tremendous gains in performance. See the Final Drive Ratios and Horsepower and Torque curve in this section. Gains of over 40 horsepower and 60lbft. or torque are easily achieved without any modifications to the engine.


The our overdrive also gives you an important “towing” overdrive gear that is between the tall factory ratio and Drive (3rd). This gear will giveyou 11% more torque multiplication and lower transmission temperatures by as muchas 100 degrees when compared to factory overdrive. Some of these vehicles with lowrear gears can also make use of double overdrive when running empty.


4L80E’s used in motorhome's and trucks have a .75 overdrive ratio very similar to Gear Vendorss .78 but the factory unit tends to unlock and lock (hunt). The Gear Vendorss will not hunt and will also reduce temperatures in the main transmission by as much as 100 degrees on warm days. Consequently all our customers tow in the GV ratio and greatly extend the life of the transmission.


Trucks running empty can make use of double overtime for great economy and extended engine life. Motorhome's present too large a frontal area to the oncoming wind to make double overtime practical but because they are always loaded they greatly need the Gear Splitting and alternative Overdrive features of the Gear Vendorss.


Gear Splitting is the feature that allows the OVERDRIVE to shift between the gears. You will now have approximately 1/2 the drop of engine rpm from one gear to the next when you want power. This is why this overdrive will give you more power than any underdrive or overdrive on the market. By keeping torque multiplication higher and engine rpm narrower you increase engine performance by typically more then 40hp and 60lb ft. of torque without any modifications to the engine (see Final Drive Ratio charts and Horsepower and Torque curves in this section) (see also common questions on performance modifications).

Gearing is what you are buying when you purchase a Gear Vendorss Under/Overdrive. If you take a few moments to study the gear chart for your transmission and rear end ratio combination you will se why this product is so popular.


This is why big trucks (Kenworth's, Peterbelt's etc.) use gears (most 18 wheelers have 15 to 21 gears) instead of modifications. Because gearing gives them performance which actually improves the reliability of the engine. The heavier you are loaded the more you need our overdrive.


If you already have engine modifications (chips, exhaust, fuel increases, etc.) our overdrive will let you get the most from them through workingin narrower rpm ranges when loaded and also by adding torque multiplication to makeit easier on the engine and transmission, helping to keep the temperatures down.


The Gear Vendorss comes with a 2-year unlimited mileage warranty (on non commercial applications) and a 30 day money back guarantee that you will love the performance (see warranty for details). The Gear Vendorss is the only after market performance device or auxiliary transmission that comes as original factory equipment on new cars, trucks, vans or Motorhome's.   Over 1 million in the 80’s and 90’s were installed by manufacturers on vehicles; i.e.; Ford Diesel Transit Vans (European market), Volvo gas and diesel, Fleetwood, Allegro, Rexhall, Monoco and others Motorhome's and GM’s Twin Turbo Callaway Corvette.

If you’re vehicle is heavily loaded or you just love performance our Gear Vendorss Overdrive is the ultimate option. Call our customer service line @ (800) 316-1632 and we will arrange for purchase and installation or by your preferred mechanic.


GM 4 Speed Automatic Performance Car/StreetRod

The 700R4/4l60E was designed for improving GM’S CAFÉ (Corporate Average Fuel Economy) ratings. Because of this it has a very low 3.06 1st gear and a very tall .70 overdrive ratio. This makes it the widest ratio automatic transmission on the planet (rear wheel drive) with only 4 gears. The Gear Vendorss fixes the wide ratio problems so that when you want performance you have a gear between each of the factory ratios. This gives you approximately half the drop in the engine rpm and torque multiplication (see final drive ratios).

You can easily have increases in horsepower in the 50+ range and torque boosts of 70lb ft. just by gear splitting.  With 8 forward gears availablethe motor stays in a narrow rpm band of performance.  The .78 ratio of the Gear VendorsS gives an alternative overdrive ratio to the very tall factory gear and the Gear Vendorss can be used with virtually unlimited horsepower. If you have a car or hotrod truck, also read the 3-speed 2wd section. If you have a truck used for towing, read also the GM 4-speed automatic truck section.

Final Drive Ratio 700R4/4L60E 4-Speed Automatic Overdrive
     Axle Ratio

  Rear End Ratio








Transmission Ratio


Final Drive Ratio


















































4th GM O/D








Double Over









Final Drive Ratio 4L80E 4-Speed Automatic Overdrive  

Axle Ratio

  Rear End Ratio 5.13 4.88 4.63 4.56 4.1 3.73 3.42
  Trans Ratio

Final Drive Ratio

1st 2.48 12.72 12.1 11.48 11.31 10.17 9.25 8.48
Over 1.93 9.92 9.44 8.95 8.82 7.93 7.22 6.6
2nd 1.48 7.59 7.22 6.85 6.75 6.07 5.52 5.06
Over 1.15 5.92 5.63 5.34 5.27 4.73 4.31 3.95
3rd 1 5.13 4.88 4.63 4.56 4.1 3.73 3.42
Over 0.78 4 3.81 3.61 3.56 3.2 2.91 2.67
4th GM O/D 0.75 3.85 3.66 3.47 3.42 3.08 2.8 2.57
Double Over 0.59 3 2.85 2.71 2.67 2.4 2.18 2

 Gear Vendors Overdrive GM 4 speed automatics Products 




Chevrolet/GMC Application Guide 2 Wheel Drive 4-Speed Automatic
Part Number Transmission Comments Description
3DFS4L61A Automatic 4-Speed 700R4/4L60E - 6 Bolt Tailhousingailhousing. Replaces 6 bolt Requires Callaway Corvette rear tail case assembly, and modifications to stock torque arm. nd modifications to stock torque arm.
3DFS700A Automatic 4-Speed 700R 4/4L60 - 4 Bolt Housing Mechanical Speedoousing - Mechanical Speedo. Replaces 7" tailhousing. Transmission mount not provided on GV adapter. Must modify factory crossmember.  modify factory crossmember.
3DFS701A Automatic 4-Speed 700R 4/4L60 - 4 Bolt Housing Electric Speedoousing - Electric Speedo. Replaces 7" tailhousing. Transmission mount not provided on GV adapter, must modify transmission crossmember.  modify transmission crossmember.
3D4L60A Automatic 4-Speed 4L60E - 4 Bolt Housing. Replaces 7" tailhousing. 93-95 small block vans and trucks with electric speedometer. meter.
3D4L60E Automatic 4-Speed 4L60E - 4 Bolt Housing. Replaces 7" tailhousing. 96-98 small block vans and trucks with electric speedometer. meter.
3D4L60G Automatic 4-Speed 4L60E - 4 Bolt Housing. Replaces 7" tailhousing. 99-02 small block vans and trucks with electric speedometer. meter.
3D4L61A Automatic 4-Speed 4L60E - 6 Bolt Housing. Replaces 6 bolt housing. 96-98 GM with 6 bolt extension housing.
3D4L61E Automatic 4-Speed 4L60E - 6 Bolt Housing. Replaces 6 bolt housing. 99 and newer with 6 bolt extension housing.
3DFS4L61E Automatic 4-Speed 4L60/ 4L60E 6 Bolt Tailhousing - Electric Speedo Replaces 6 bolt tailhousing. Requires relocation of front torque arm mount.
3DFS4L68 Automatic 4-Speed 4L65 Torque Tube Mountnt. Replaces torque tube. 1997-2005 C5 Corvette.
3D4L80A Automatic 4-Speed 4L80E. Replaces 6 1/8" tailhousing. 91-93 GM gas and diesel applications.
3D4L80E Automatic 4-Speed 4L80E. Replaces 6 1/8" tailhousing. 94-95 GM gas applications.
3D4L80G Automatic 4-Speed 4L80E. Replaces 6 1/8" tailhousing. 96-98 GM gas applications.
3D4L80I Automatic 4-Speed 4L80E. Replaces 6 1/8" tailhousing. 94-01 GM diesel applications.
3D4L80K Automatic 4-Speed 4L80E. Replaces 6 1/8" tailhousing. 99-02 GM gas applications.
3D4L80M Automatic 4-Speed 4L80E. Replaces 6 1/8" tailhousing. 03 and up GM small block gas engines.
3DFS4L60E Automatic 4-Speed 4L60/E - 4 Bolt Tailhousing - Electric Speedoing - Electric Speedo. Replaces 7" tailhousing. Must relocate forward torque arm mount.