Overdrive Unit, Common Questions

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Isn’t it just an overdrive?
Which is better an underdrive or an overdrive?

No competing underdrive or overdrive on the market will give you the performance of a Gear Vendors UNDER/OVERDRIVE. In fact you could install both an underdrive and an overdrive of insidevend_large.jpgany other brand and still not have the performance of a Gear Vendors . The only thing an underdrive could do, that the Gear Vendors products will not, is get you a gear below 1st but for the few times this would be of any value virtually all customers would greatly prefer the performance, features, and other benefits of a Gear Vendors .

Let’s cover the differences between a Gear Vendors and competing products for automatictransmission equipped vehicles (manual customers should read this but understandthat outside of racing we do not recommend you use your clutch when shifting). Allother brands of auxiliary transmissions are simply dual ranges. They are meant tobe put in low range when you are towing and high ranges when you are not. But theproblem is that your vehicle has too few gears. Simply making your gears all loweror taller still leaves you with the same gap between each gear. So you could actuallygo slower with a dual range than you do now. You could shift these products whilemoving (one of them you need to go to neutral before you can shift and the otherhas no synchros but will perform a non-synchronized shift if you let off the gas),but these products are simply not designed to shift behind automatic transmissions.


The Gear Vendors, on the other hand, is built like an automatic. It has the expensiveand reliable reaction planetary system, which is why it’s compact and cylindricalin shape like your automatic. The Gear Vendors is designed to shift under any andall throttle conditions continuously, so when you need power you can go up or downjust half a gear at a time (Gear Splitting). Sure the Gear Vendors has always beenthe most expensive, but it also offers far greater performance and quality.

After the Gear Vendors is installed in your vehicle you will have twice as many underdriveratios as you do now (1st, 1st-over, 2nd, 2nd-over) plus an overdrive gear (3rd-over)suitable for towing. If you also have factory overdrive you will now have 3-overdrivegear choices. Six or eight forward ratios that you can shift to sequentially, oneafter the other, for power unmatched by any other auxiliary transmission. There aremany more differences i.e.: Automatic shifting, pressurized lubrication, fluid filters,4500# roller clutch, etc, .

The trademark UNDER/OVERDRIVE refers to the fact a Gear Vendors is a unique overdrive.One that can do everything both an underdrive or overdrive can do, better than anyunderdrive or overdrive available, except get you a gear below first.

MANUAL TRANSMISSION customers also gain several unique benefits related to horsepowerhandling, ease of shifting and other specific engineering differences between theGear Vendors and other auxiliary transmissions. All other brands of auxiliaries arethemselves small manual transmissions, so in order to gear split with any competingproduct you will either have a 2nd shift lever to move (difficult) or a non-synchronizedbox controlled by a button (not intended to shift often). Only the Gear Vendors istruly a convenient Gear Splitter and designed to withstand the abuse of shiftingcontinuously.

The idea that just having lower gears when towing or taller gears when running emptyis not going to solve most customers problems. The problem is that there is too muchrpm drop between some gears to maintain performance on grades and while towing. Anothersignificant advantage with the Gear Vendors is that you can do all your towing withyour main transmission in 1 to 1 (direct drive no gears) not to overdrive, usingthe Gear Vendors to take the stress of overdrive.


This greatly lowers transmission temperatures and extendsits life. We have many commercial customers that have found the main Trans reliableif they only use the factory overdrive gear when empty.

The Gear Vendors is the most expensive auxiliary transmission you can buy but itdoes more with more technology and performance than any other brand.


Largely what makes Gear Vendors successful is the founding philosophy of the company. To offer the most advanced, highest quality, auxiliary transmission, with the best customer service available. award.jpgPrice was not then or now a part of the mission statement. There may be some market for cheap products that are not of quality but not in the markets we serve. Gear Vendors are popular with RV’s, trucks, High Performance and Racing applications. These are vehicles which are not retired even when they are very old unless damaged. It just doesn't’t make sense to put anything less than the best product in vehicles this valuable.

In order to be the Best we had to have the best product. The product design is ultimatelythe most important aspect and it is know worldwide as one of the best designed transmissionsever. Gear Vendors did not invent overdrive or the original patents on our product.DeNormanville (maybe the most famous transmission designer ever) created the originalproduct which, GKN (a 6 billion dollar/year public automotive conglomerate) acquiredto produce this product for Ford and Volvo. Gear Vendors is a licensed manufacturerfor GKN and in 1979 started applying racing expertise to the original design. Thehighest honors in the industry were won by Gear Vendors in 1981 with SEMA’s BestEngineered award and again in 1989 (this unprecedented 2nd award for the Ptype configurationis the only time SEMA has given the engineering award twice on the same product bya manufacturer). No competing product has even one such award.

One of the big factors in Gear Vendors success is that our customers know exactly what benefit they get from our product. You interact with a Gear Vendors, turning it on and off. When it is “off” it is just like the vehicle was stock, so our customers get a “before & after test” every time they drive. This makes our customers our strongest salesmen for the product and is why we have dealt with many customers on five or more different vehicles over the course of the last 20 years. Today, many new Truck and Motorhome dealerships put Gear Vendors in prior to the customer even taking delivery of their new vehicle because the customer or dealer felt they needed one or the customer had one on the trade-in and wouldn't’t be without it.

Prior to the factory overdrives becoming available many vehicles in the 1980’s and early ‘90’s came factory with the Gear Vendors as either optional or standard equipment. These manufactures included Allegro, Fleetwood, Monaco, Executive, & Rexhall motorhome's. GM’s Callaway Corvette, Volvo passenger cars and Ford Diesel Transit vans. Between Gear Vendors and GKN’s production more than 2 million new vehicles have come factory equipped with our product and the lighter duty earlier version. No manufacturer has ever equipped a vehicle with any other auxiliary transmission that you can buy.

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.