GM 3-Speed Automatic Truck/Motorhome

GM 3-Speed Automatic Truck/Motorhome


With the GEAR VENDORS dashswitch in “auto” you will have automatic overdrive just like the vehicle came with a factory system. The GEAR VENDORS will shift on and off without attention of the driver and can be used while towing up to combined weights of 30,000 lbs. An interactive floorswitch is positioned for the left foot (just like a headlight dimmer) to give manual control at any moment so that you can turn the overdrive on/off for performance and gear-splitting.

Performance while accelerating or climbing grade is greatly improved by the torque multiplication of 6 forward ratios (see Final Drive Ratios). With 1/2 the drop in engine rpm on each gear change, the engine, transmission, and torque converter stay in the power band running stronger and with lower exhaust gas temperatures.

Most importantly you are getting this horsepower and torque without modification in any way to the engine. Any other way of increasing power (chips, induction, exhaust, fuel) all put stress beyond the original equipment. With the GEAR VENDORS UNDER/OVERDRIVEâ„¢ you get this power because gears are multipliers of torque, plus the engine can be kept in a narrower (better performing) rpm range when power is needed. For this reason, if you have performance modifications the GEAR VENDORS also helps them work to their maximum potential. Not only do you get performance without engine modification but the overdrive will pay for itself in fuel mileage alone. Add to this the wear savings you get from slowing the engine down 22% so that the same rpms that currently take you only 500 miles will now take you 640 miles.


Most vehicles will experience a mileage increase of 22-28% (the reciprocals of our ratio) if driven at the same speeds as they were without the GEAR VENDORS. No single change to your vehicle can increase mileage and reduce engine wear as effectively, which is why all vehicles today come factory with overdrive.

The GEAR VENDORS UNDER/OVERDRIVEâ„¢ will do more for this vehicle than any Underdrive or Overdrive ever offered. You will get all the features normally associated with an underdrive except a gear below first, plus all the economy of overdrive. Because GEAR VENDORS is the only product you can shift under throttle you will have far greater performance and economy. The GEAR VENDORS comes with the best warranties in the industry (2 years for noncommercial use) including a 30 day money back guarantee (see Warranty for details). It is without question the best item you ever bought for your truck or RV or your money back. This is our 27th year – we know you’ll love it.



It is the gear under your seat that counts.Gearing is what you are buying when you purchase a Gear Vendors 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. The Final Drive Ratio shows you how many times the engine turns for one complete turn of the tires. Gears are multiplier of torque. The mathematical equation for Horsepower is; Torque X RPM/5252 = HP. Close ratio gearing lets us work both the torque and rpm side of this equation for big gains in HP and performance. Notice for instance that 1st-over has a lot more torque multiplication than 2nd – now look how low you would have to go in rear end ratio to make your second gear have as much torque as 1st-over. Same with 2nd-over compared to 3rd.

Whatever your 2nd-over final drive number is – that is equivalent to having that ratio for a rear end torque multiplier. Of course, with gear-splitting we are keeping the engine rpm up from one shift to the next and further exploiting the ratio benefit.

There is not room here to cover all the details (like the benefit to passing gear and such) so call us at the factory to discuss your exact application – we have customer service guys on hand for you to ask these types of questions.

 Axle Ratio4.564.103.733.553.423.08
 Trans RatioFinal Drive Ratio
 Axle Ratio4.884.564.103.733.553.42
 Trans RatioFinal Drive Ratio

CHEVROLET / GMC Application Guide 2-Wheel Drive 2/3- Speed Automatic