Common Questions


Fuel Economy – how much will my vehicle gain?

All GEAR VENDORS products come with a money back guarantee so you know you can realize the mileage gains we claim *see warranty for details.

Cars — virtually any car that does not have a factory overdrive gear is going to gain 22-28% typically by adding the GEAR VENDORS OVERDRIVE. Exceptions would be a car with say an unusually tall diff gear like say 2.73 where the engine really is quite low in rpm at cruise already. But for all us performance guys who run 3.42 to 4.10s you are looking at something near 25% gain in mpg at highway speeds. If your car has forced induction (supercharger) plan on even bigger gains — not uncommon for blown car to get 100% better fuel economy with the GEAR VENDORS simply because the overdrive is also slowing down the blower, plus reducing heat internally in the blowers charge area.

Trucks — For diesel trucks (when not towing) you want to get the engine around 1600-1800 at cruising speeds — gas truck at around 2200-2500. This means virtually any older truck that does not have overdrive is typically going to gain 22-30% on mpg by adding the GEAR VENDORS OVERDRIVE. Having said that, today our most common sale to trucks is the late model diesel that already has overdrive but still too high of rpm. When not towing these late model diesels can run double overdrive (the factory overdrive gear plus the GEAR VENDORS). The categories certain to gain 20% plus include. Ford GM and Dodge diesels with manual transmissions and 3.73 or stouter diff ratios and automatics with 4.10s or higher numerically (this is because the automatic trans has a taller overdrive ratio from the factory). We do have a lot of automatic customers with 3.73 gears that love their GEAR VENDORS and claim 15% or better increases but call us so we can discuss with you the terrain which you commonly drive — should be a lot of flat land cruising to be most beneficial.

Motorhomes — because of the aerodynamic loads of the big box shape, motorhomes fall into two categories. Those with factory overdrive and those without. Without factory overdrive you absolutely need a GEAR VENDORS. 22-28% gains typical on all three speed automatics, plus all the other benefits of gear-splitting ratios etc. for climbing hills and towing. For Motorhomes with factory overdrive the big gains are in the ability to climb hills with better splits in the ratios. Running double overdrive is not practical for saving fuel except in those instances where you have a tail wind because it is really the aerodynamics the dictate the horsepower you need. This is why a motorhome gets big mpg gains by just slowing down to 60 instead of 70mph.

I have a 3 speed auto and was thinking of a 700R4 swap to get overdrive, but I am wondering how a GEAR VENDORS would be better?

So the Muscle car guy is the GEAR VENDORS customer. The big block era of 1967-72 our most popular years for this same reason — heavy car, big horsepower, and the need to be able to perform. We of course do a ton of 55-66 cars as well (both restorations and performance builds). The 3 speed automatics built in the big block era by the big three are the best transmissions for performance street/strip use. You certainly do not want to take out a 727 or 904 Mopar trans, or a c4 or c6 Ford ,or a TH350 or 400 GM, and put in the lighter duty 700R4 or even a 4l80E. Hot Rodding is making improvements not compromising performance. It may be some fun to change an intake manifold or do other work in the engine bay (where friends can see the new stuff) but when it comes to transmissions you want to do this work exactly once. You want the best. The best performance, the most reliability, a trans package that can handle anything you throw at it and the strongest overdrive
on the planet is a GEAR VENDORS. That is why a GEAR VENDORS comes with a 2yr unlimited horsepower warranty (we know you will hurt the main trans before you ever hurt our overdrive) even at the dragstrip. We own records in cars with 2000hp.

I own a 4 speed manual transmission but was thinking of either bolting on a GEAR VENDORS or swapping in a late model 5 or 6 speed. What would be better?

The answer to this question is much like the same question automatic guys have when they have a 3speed auto and are thinking of maybe a late model overdrive automatic swap — so read that question also after you have read the following.

Muncie M20, M21, M22, Borg Warner T-10, Ford Top Loader, and Mopar A833’s are the best manual transmission ever made for performance street/strip use and abuse. This is why they are still used in Nascar. As soon as you put a 5th gear in the trans you compromise a lot of strength. So the late model 5 or 6 speed will not handle as much horsepower. The 4 speed muscle car era transmission are also much easy to shift fast (you really cannot powershift a late model five speed) where you feel like you would break the Hurst shifter off in your hand before hurting a quality 4 speed.

The moment you bolt a GEAR VENDORS to your 4 speed you have not only added the strongest overdrive gear but one that can also fix any wide ratio issues with M20 or T10 transmissions for a true six speed. Also all the 4 speed tranny’s will get a full throttle clutchless shift you can use at any moment on the street or strip. This means you can drop the clutch in 1st gear and then hit the GEAR VENDORS shift button on your shifter at full throttle and get a new ratio clutchless that will make a big difference in 100ft times and performance. For this reason we supply our 6speed badges with all 4speed kits.

It just makes no sense under any condition to remove a quality 4 speed and replace it with a late model swap. If you have a 3speed manual than yes it would be cheaper maybe to do a 5speed swap than to buy both a 4speed and a GEAR VENDORS. But if you love performance and plan to get on it at all — the GEAR VENDORS is the way to go. 2 year unlimited horsepower warranty that is guaranteed even at the dragstrip. Those 5 speed ads may show a car at the dragstrip but the truth is they will either deny your warranty if you drag race or give you such a short warranty it would not matter. By the way — the GEAR VENDORS is also much easier to install than a swap.

A quality 4 speed manual and GEAR VENDORS planetary overdrive is the strongest manual trans package you can do without going to exotic race only manual transmissions.

For more details on this subject click here.

Why is a GEAR VENDORS overdrive stronger than a factory overdrive automatic or manual?

GEAR VENDORS is the strongest overdrive you can buy because that is what our company has always intended to build. The automobile manufacturer has a wide group of customers to please. Probably 99% of these customers will never go to a dragstrip, do not like firm shifts from the transmission, and could care less about a 10th off their hundred foot time. GEAR VENDORS shift firm like a shift kit in an automatic and use a common vertex cone clutch that is low in parasitic loss and cannot slip. GEAR VENDORS uses super high quality materials like 300m steel, drop forged annulus, and 18 element roller clutch that are incredibly strong, expensive, and just overbuilt for the typical new car buyer. GEAR VENDORS are also assembled by hand to exacting stacked tolerances that would be impractical to build by the thousands per day — we build only about 3 thousand per year.

So, it is not that we are smarter than the automotive manufacturers, in fact there are no secrets in the transmission industry, everything any of us do is patented and those patents are well laid out for all to see. GEAR VENDORS is just more targeted to the performance/race customer who is willing to pay for a higher level of performance, components and assembly. GEAR VENDORS has also been making planetary overdrives longer than anyone in the automotive industry. We were suppliers to GM for the Twin Turbo Callaway Corvettes. A lighter duty version of our product was used in Ford Diesel Transit vans in the european market for 10 years. Chrysler and GEAR VENDORS have worked on a couple transmission projects that led to engineering still in use today. So when we show how much stronger one of our components are – it is not criticism in any way, it is just that our markets are different.

Can I run a high stall converter in overdrive with a 3.42 axle?

Yes, this is one of the most often confused questions (even when you ask people you would think would be knowledgeable). Here is the detail. Our example could be this 3.42 Chevy guy. In overdrive he is going to be a 2.67 final drive ratio. He is a Cutlass body with 27 inch tire and so at 75mph in overdrive the motor will be turning 2484 rpm and he has a 3500 stall speed on the back of a pretty nicely built 350ci motor making close to 400hp. 95% of the people you would ask (even tranny guys) would say no-way and yet we know this is an awesome package (drives wonderful, no high temps in the trans etc) why does it work? When his converter was made it was set up to stall at 3500 with 400hp. However if you put 600hp to it it would stall at something like 4500. Conversely if you only put 125hp to it (as when you are just crusing at 75mph not accelerating) then the stall is way down at 2,000 rpm. So his stall with a 3500 converter is not 3500 at cruise because he is not making 400hp. Car drives wonderful. If he romps on it while cruising then the trans is going to downshift to a lower gear and get him into the powerband. (note: read gear vendors passing gear in this section) So, this is why you never lie to you converter builder (because if you overstate your hp you will not get the stall you wanted).

The package of 3500 and 3.42 with 400hp is a sweet setup with a GEAR VENDORS . Without a GEAR VENDORS the trans will not have a great passing gear because 2nd is too low. But with a GEAR VENDORS it will it will jump right into 2nd-over which will rip nicely and put the converter right in the power. You can use this setup as a guidline and say move up or down in ratio related to stall from this good setup with a GEAR VENDORS. Below you will see we have listed an actual formula for Aerodynamic load.

Aerodynamic drag force may be defined as follows:
Fd = (1/2) Cd r A V^2 (1)

Fd = aerodynamic drag force
Cd = coefficient of drag
r = density of air
A = frontal area of vehicle, into the direction of motion
V = velocity of vehicle, into the direction of motion

Can I switch a GEAR VENDORS that was behind my automatic to a manual trans or vice/versa?

Yes, one of the cool things about a GEAR VENDORS is that it is an auxiliary transmission. It is the same overdrive for virtually all the different applications with just different extension housings and shaft input couplings. In most cases it is in the 700 dollar neighborhood to switch these components to the new application you need. If you are selling the vehicle though, don’t take it out. Most vehicles (especially the collectible years) will gain in value by having the overdrive as everyone knows they are expensive and really add to the performance and economy. Plus many buyers recognize they get these benefits while still leaving the period correct transmission in place with just the overdrive added. So in the long run, if you own a cool car or truck the overdrive really doesn’t cost you anything and you get to keep the added fuel economy, saved wear and tear on the drivetrain, and performance gains as a bonus.


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 any 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 difference between a GEAR VENDORS and competing products for automatic transmission equipped vehicles (manual customers should read this but understand that outside of racing we do recommend you use your clutch when shifting). All other brands of auxiliary transmissions are simply dual ranges. They are meant to be put in low range when you are towing and high range when you are not. But the problem is that your vehicle has too few gears. Simply making your gears all lower or taller still leaves you with the same gap between each gear. So you could actually go slower with a dual range than you do now. You could shift these products while moving (one of them you need to go to neutral before you can shift and the other has 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 expensive and reliable reaction planetary system, which is why it’s compact and cylindrical in shape like your automatic. The GEAR VENDORS is designed to shift under any and all throttle conditions continuously, so when you need power you can go up or down just half a gear at a time (GearSplitting). Sure the GEAR VENDORS has always been the 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 underdrive ratios 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-overdrive gear choices. Six or eight forward ratios that you can shift to sequentially, one after the other, for power unmatched by any other auxiliary transmission. There are many more differences ie: Automatic shifting, pressurized lubrication, fluid filters, 4500# roller clutch, etc., that youcan read about elsewhere in this web site.

So, our trademark UNDER/OVERDRIVE refers to the fact that a GEAR VENDORS is a unique overdrive. One that can do everything both an underdrive or overdrive can do, better than any underdrive or overdrive available, except get you a gear below 1st.

MANUAL TRANSMISSION customers also gain several unique benefits related to horsepower handling, ease of shifting and other specific engineering differences between the GEAR VENDORS and other auxiliary transmissions. All other brands of auxiliaries are themselves small manual transmissions, so in order to gearsplit with any competing product you will either have a 2nd shift lever to move (difficult) or a non-synchronized box controlled by a button (not intended to shift often). Only the GEAR VENDORS is truly a convenient GearSplitter and designed to withstand the abuse of shifting continuously.

The idea that just having lower gears when towing or taller gears when runningempty is not going to solve most customers problems. The problem is that there is too much rpm drop between some gears to maintain performance on grades and while towing. Another significant advantage with the GEAR VENDORS is that you can do all your towing with your main transmission in 1 to 1 (direct drive no gears) not in overdrive, using the GEAR VENDORS to take the stress of overdrive.

This greatly lowers transmission temperature and extends its life. We have many commercial customers that have found the main transmission reliable if they only use the factory overdrive gear when empty.


Exhaust Systems, and Performance Chips, etc.?

These components are actually our #1 competitor. We at GEAR VENDORS are quite honestly gearheads. We are definitely biased towards performance through GearSplitting. We believe the best way for any vehicle which works hard (trucks and RV’s) to increase performance is by leaving the engine factory stock and increasing the torque multiplier (gears) and the time you’ll spend in the rpm where the engine was designed to make great power.

Every vehicle does need a quality exhaust system. In fact, most new vehicles come with 7 to 10 years warranted systems tied to emissions compliance. All these new vehicles have exhaust systems of much higher quality than what were available 10-years ago. Having said that, there are some aftermarket exhaust companies making some outlandish claims. If you are looking to replace a rotted out exhaust system and pick up 10-20hp you might find it here. Maybe even 30hp if you go for an aggressively loud system. But some manufactures are claiming 60+. One or more claim 80hp. The only way to get this hp change (assuming the stock system is in good condition) is by either putting in more fuel or revving the engine harder. This is why many of these supposed exhaust systems include alterations to the fuel pump or the addition of intercoolers (diesels) or fuel mapping (gas) and/or shift program changes to the transmission. But at what cost? These are not the primitive 2-barrel carburetors or outdated point ignition systems we had in our old cars. Today’s engines have the best of everything. Modifying the engine to make the output higher can definitely reduce engine life.

If you own a truck and never tow you are the most reasonable candidate for this kind of power modification because you are never really working the truck against a load that the truck rating assumes. You will make more power off the line but during most of your use you are just cruising and not making additional power.

However, for those who do tow, you vehicle is working significantly harder for long periods of time. The more aerodynamic load you have and the harder you push against either a weight load or speed (aerodynamics) the less you can afford engine type modifications.

Ford, Dodge and GM have to assume you are at the full gross vehicle rating all the time and set the engine accordingly. If you set up your power for running empty and then occasionally weight the truck, many components will be at higher stress than intended. This is why the GEAR VENDORS is such a great way to make power, because it takes the conservative settings the manufacturer intended for the engine and multiplies torque and your ability to stay in the designed power without over-revving or lugging the engine. Increased performance that is actually better for the vehicles. This is the same reason you would find that the big 18 wheelers like Peterbuilts and Kenworths have large conservative output engines with 5 & 6 speed manuals and 2 or 3 speed auxiliary transmissions for 10 to 15 or more forward ratios.

There is simply no better way to make conservative gains in horsepower and torque than a GEAR VENDORS UNDER/OVERDRIVE™.


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. Price 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 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 ultimately the most important aspect and it is known worldwide as one of the best designed transmissions ever. GEAR VENDORS did not invent overdrive or the original patents on our product. DeNormanville (maybe the most famous transmission designer ever) created the original product which, GKN (a 6 billion dollar/year public automotive conglomerate) acquired to produce this product for Ford and Volvo. GEAR VENDORS is a licensed manufacturer for GKN and in 1979 started applying racing expertise to the original design. The highest honors in the industry were won by GEAR VENDORS in 1981 with SEMA’s Best Engineered award and again in 1989 (this unprecedented 2nd award for the Ptype configuration is the only time SEMA has given the engineering award twice on the same product by a manufacturer). No competing product has even one such award.

One of the big factors in our success is that our customers know exactly what benefit they get from our product. You interact with a GEAR VENDORS, turning it on an 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 salesman 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 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 manufacturers included Allegro, Fleetwood, Monaco, Executive & Rexhall motorhomes, 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.

The Founder and CEO of GEAR VENDORS is Ken Johnson and his primary directive year after year is customer satisfaction. Many policies at GEAR VENDORS relate to this commitment. Our products have always been the DeNormanville designed reaction planetary and roller clutch. These components are of such quality that the same unit we sell for an RV or Truck goes to Drag Racers with 1200+ horsepower. This component design also means many reliability features for the consumer i.e: you cannot get stuck in neutral as you can with other products. GEAR VENDORS also has the best warranties in the industry up to twice as long as competing products. Automatic transmission equipped vehicles not used commercially get a 2-years unlimited mileage warranty. Many of our commercial customers put on more than 200,000 miles per year so we limit truck manual transmission and all commercial use to 1-year, 25,000#GCVW, unlimited mileage. (See Warranty for details).

The Founder and CEO of GEAR VENDORS is Ken Johnson and his primary directive year after year is customer satisfaction. Many policies at GEAR VENDORS relate to this commitment. Our products have always been the DeNormanville designed reaction planetary and roller clutch. These components are of such quality that the same unit we sell for an RV or Truck goes to Drag Racers with 1200+ horsepower. This component design also means many reliability features for the consumer i.e: you cannot get stuck in neutral as you can with other products. GEAR VENDORS also has the best warranties in the industry up to twice as long as competing products. Automatic transmission equipped vehicles not used commercially get a 2-years unlimited mileage warranty. Many of our commercial customers put on more than 200,000 miles per year so we limit truck manual transmission and all commercial use to 1-year, 25,000#GCVW, unlimited mileage. (See Warranty for details).

All customers get a 30 day money back guarantee (see Warranty for details) so you can drive it and know you got the quality you paid for. GEAR VENDORS customer service personnel are knowledgeable in every aspect of use and installation and available to you free of charge whether you purchased our system 2 weeks ago or 2 decades ago. Also, as an extension of our customer service, should you own the product long enough to need a replacement, any customer who owns one of our units can replace it for 1/2 the cost of new. This kind of commitment to the existing customer is unheard of in most businesses today, but not at GEAR VENDORS.

In summary, GEAR VENDORS has the best quality, product, and service, not necessarily because we are smarter or nicer than the competition (though we may be) but because at GEAR VENDORS that is what we always intended.