Ford 4-Speed Auto

FORD 4 & 5 Speed Automatic – Cars / Trucks / Motorhomes


There are two basic Ford 4-Speed automatics: The light duty AOD/4R70 found mainly in half ton or lower applications, and the heavy duty E40D/4R100 in the heavy 1/2 plus all 3/4 and 1 ton trucks and motorhomes. These transmissions have a low first gear which is good for initial take off but this makes the transmission have very wide ratio changes. The intention by the designers was the best possible EPA mileage ratings, not performance.

The GEAR VENDORS will give you Gear-Splitting to fix those wide ratios with a gear between each of them when you want it for tremendous gains in performance (see Final Drive Ratios). Whether you are accelerating with a Supercharged sport truck or climbing a hill with a heavy load in two behind your diesel – gear-splitting = performance.

GearSplitting is the feature that allows the UNDER/OVERDRIVEâ„¢ to shift between the gears. When you want power you will now have approximately 1/2 the drop of engine rpm from one gear to the next. By keeping torque multiplication higher and engine rpm narrower you increase engine performance by typically more than 40hp and 60lb ft. of torque without any modification to the engine (see Horsepower and Torque curves) (see also, Common Questions on performance modifications).


This is why big trucks (Kenworths etc.) use gears (most 18 wheelers have 10 to 15 gears) instead of the other modifications, because gearing gives them performance which actually improves the reliability of the engine. The heavier you are loaded, the more you need a GEAR VENDORS.

Fuel Economy: Besides giving you 8 gears and lots of performance the Gear Vendors Under/Overdrive is the most effective way to improve fuel mileage on vehicles running a 3.73 or higher numerical rear gear (ie 4.10, 4.88). Expect 20% increases during highway cruising with any rear gear in the 4’s and 10-15% with a 3.73 with any big block engine gas or diesel. Small block V8 engines (4.6, 5.0, 5.4) do not have the bottom end torque to push the trucks aerodynamics in double overdrive so on the small blocks your factory gear should be good (with the exception of the supercharged small blocks).

Look at the Final Drive Ratios and notice that you will now have 3 different ratios of overdrive. Double overdrive for when running empty with your truck (no towed load), factory overdrive for in-town 60mph runs, and a .78 overdrive ratio for when towing that will give you more torque multiplication and cooler transmission temperatures (extending the life of your transmission) without any cost to fuel mileage.


If you have a rear end of 4.10 or greater and commonly drive the truck without a load, the Gear Vendors is going to pay for itself very quickly and bring a lot of enjoyment to driving the truck with lower engine noise better fuel mileage and of course the performance aspects of gear-splitting always available.

If you already have engine modifications (chips, exhaust, fuel increases, etc.) the GEAR VENDORS will let you get the most from them by working in narrower rpm ranges where the horsepower is. Also, by adding torque multiplication the GEAR VENDORS makes it easier for the engine and transmission to propel the vehicle.

On the 5 speed 5R110w you will notice virtually all the same benefits as the 4 speeds but two are most important – Double overdrive when running empty for fuel economy identical to the 4speeds comments above, and 3rd-over which when towing and climbing grades is invaluable a it is 28% faster than 3rd but 20% more torque multiplication than 4th (equivalent to putting a 4.89 rear instead of your 4.10).

The GEAR VENDORS comes with a 2 Year unlimited mileage warranty (1yr if you have a commercial truck – see Commercial section) and a 30 day money back guarantee so you know you will be happy with everything about how this unit installs and drives (see Warranty for details). The GEAR VENDORS is the only aftermarket performance device or auxiliary transmission to come as original factory equipment on new cars, trucks, vans and motorhomes.

With fuel prices what they are today, there is just no good reason to own a Gear Vendors Under/Overdrive. Call us and we will answer any questions and gladly arrange for purchase and installation at your authorized local dealer of your preferred mechanic.



Find your transmission and rear gear multiplier 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 the best is because of its sophisticated planetary construction. This means GEAR VENDORS is the only auxiliary intended as a GearSplitter 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 lift off the accelerator or is not intended to shift frequently is not going to give you this performance.

There is not room here to cover all the details so call the factory to discuss the full benefits demonstrated on these charts.


    Axle Ratio
    5.38 5.13 4.88 4.63 4.30 4.10 3.73 3.55
  Trans Ratio Final Drive Ratio
1st 2.71 14.58 13.90 13.22 12.55 11.65 11.11 10.11 9.62
Over 2.11 11.37 10.84 10.31 9.79 9.07 8.67 7.89 7.51
2nd 1.54 8.29 7.90 7.51 7.13 6.62 6.31 5.74 5.47
Over 1.20 6.46 6.16 5.86 5.56 5.16 4.92 4.48 4.26
3rd 1.00 5.38 5.13 4.88 4.63 4.30 4.10 3.73 3.55
Over 0.78 4.20 4.00 3.81 3.61 3.35 3.20 2.91 2.77
4th Ford O/D 0.71 3.82 3.64 3.46 3.29 3.05 2.91 2.64 2.52
Double Over* 0.55 2.98 2.83 2.70 2.57 2.38 2.27 2.06 1.97
*Note: Double Overdrive not to be used when towing or loaded.


    Axle Ratio
    5.13 4.88 4.63 4.10 3.73 3.55
  Trans Ratio Final Drive Ratio
1st 3.09 15.85 15.08 14.31 12.67 11.52 10.97
Over 2.41 12.33 11.73 11.13 9.86 8.97 8.53
2nd 2.20 11.29 10.74 10.19 9.02 8.20 7.81
Over 1.71 8.78 8.35 7.92 7.02 6.38 6.08
3rd 1.53 7.85 7.47 7.08 6.27 5.71 5.43
Over 1.19 6.11 5.81 5.51 4.88 4.44 4.23
4th 1.00 5.13 4.88 4.63 4.10 3.73 3.55
Over Not used   no way to hold 5R110 in 4th
5th 0.71 3.64 3.46 3.29 2.91 2.65 2.52
Double Over* 0.55 2.83 2.70 2.56 2.26 2.06 1.96
*Note: Double Overdrive not to be used when towing or loaded.

Call or e-mail the factory to find out all the options available in your performance application, 1-800-999-9555.

FORD Application Guide 2-Wheel Drive 4/5 Speed Automatics

Call Factory for Application