The one thing that remains true about classic cars is that they weren’t built with economy in mind. The cars that we love from the ‘60s and ‘70s came with 2, 3, or 4 speed transmissions, and overdrive wasn’t part of the package on those transmissions.

When the gas wars hit us in the late 1970s and economy cars hit the scene, we began to see overdrive on both manual and automatic transmissions, but it was far too late for our beloved musclecars. The past few years, however, some people have been swapping modern powertrains into their classics, and that in itself is an expensive and time consuming endeavor.

But for those who have hung on to the original engines and transmissions in their classics, there is an alternative. Gear Vendors began building overdrive units for many popular manual and automatic transmissions more than 25 years ago, giving owners of classic cars better mileage by splitting the gearing with an add-on unit that mounts directly to the back of the transmission.

The under/overdrive units became a cost-effective way to give owners of classic cars a little more time between fill ups at the gas station, and they also manage to provide better driveability and extend transmission life.

For those who have built their hot rods or musclecars, and think that they have too much power to add a simple, bolt on, overdrive, think again. Gear Vendors standard overdrive units are capable of handling upwards of 1,200 horsepower, and for serious muscle machines up to 2,000 horsepower, they simply ask you to inform them and they can make sure that your overdrive will handle the power you’re engine is putting out.

We caught up with Mike McCarthy at the Gear Vendors booth at the Spring Fling recently in Van Nuys, California, and he was there with samples of their under/overdrive units for everyone to see. For those who wanted an explanation of how these units work, there was a cool cutaway on display and McCarthy was glad to provide an explanation. We’ll be doing a full tour of their facility in the upcoming months, so be sure to check back we’ll give you the skinny on Gear Vendors.