GM Muscle Car / Street Rod / Restoration
2-Speed / 3-Speed Automatic
At about 2600 dollars (depending on model) the GEAR VENDORS is not the cheapest way
for you to get overdrive but is by far the best. A Gear Vendors will handle more horsepower,
deliver bigger performance gains, give you guaranteed trouble-free performance, and install
easier than any other overdrive available. A GEAR VENDORS will handle 1200+ horsepower
reliably and is under warranty even at the dragstrip. This is why you have seen
GEAR VENDORS in 7 & 8 second ¼ mile cars in publications like Hot Rod and National
Dragster. This is also why all GM Callaway Twin Turbo Corvettes with automatics came with a
TH400 and GEAR VENDORS instead of the 700r4 which was the base Corvette trans.
You are also going to actually make more horsepower and enjoy overdrive
cruising better with a GEAR VENDORS. For cruising you will have a dashswitch that allows
both manual and automatic operation. With the switch in "auto" the vehicle will act just like
it came from the factory with overdrive. The overdrive will kick in at 47mph or whatever the
eprom is set for in our electronics and turn back off at slower speeds without attention of
the driver. The ratio is .78 to 1 (see the final drive ratio chart below). This equates to
28% faster vehicle speed at the same rpm. Or, take your existing rear gear multiplied by .78
(ie 4.10 rear X 78 = 3.20). In this example a vehicle with a 4.10 has the same cruising rpm
as it would with a 3.20 rear when the overdrive is engaged. The 3.42 rear gear will net a 2.67
final and yet have a 6.72 1st-over gear which is nearly as strong as a 4.56 rear car in
2nd (Awesome!). Plus with this step in overdrive you can still ran a 3,500 stall converter
and cruise efficiently (see converter discussion in our "common questions" section) you're good with any torque
converter you choose for performance. Your high stall converter will hook better from gear to
gear with less drop when gear-splitting but also since the gears are closer there is not as
much need for high stall and so stock converters perform to new levels of performance when
Gear Vendors equipped.
Gear-Splitting is that feature which has made Gear Vendors so popular.
Our 1:1.286 ratio brings the same close ratios found in a close ratio Muncie to your
automatic. You will have a full 6 forward ratios and torque multiplication that will have
even taller rear gears like 3.20 and 3.42 comparing to 4.10s. When you switch to manual on
our dashswitch you control the overdrive. Pull into low, hit our button (on the shifter or
the floor) this activates our Auto-Launch feature (a red LED light up on your dash), as you
accelerate the car will rev in 1st and then shift automatically to 1st-overdrive which is a
gear ratio right between 1st and 2nd and the green light appears indicating overdrive. You
are now 28% farther down the track or road before you shift to 2nd. When you move your shift
lever to 2nd turn us off. Then rev back up and hit the button for 2nd-over (this will also
be a much higher torque multiplier than shifting to 3rd - see Drive Ratios). Then 3rd and
3rd over. You have never had this much performance, tire barking, and just plain fun driving
your car. Even at just ½ throttle it performs, and at full throttle is
just plain awesome. Look at the final drive ratios for each gear. Notice with your rear gear in
1st-overdrive how low you would have to go in a new rear gear to make 2nd gear have that
much torque multiplication. A 3.55 rear Th350 will grab 1st-over like 4.5s in 2nd.
The equation for Horsepower is: Horsepower = Torque X RPMM/5252
Gear Splitting gives you more torque multiplication and higher rpm on shift = more HP!
GM/CHEVROLET FINAL DRIVE RATIOS
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.
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
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 people who are car enthusiasts and they are here to give
you any information you could want. Look at the ratio charts here and then check out
the Magazine Articles tab. See also - See also some discussion of 700R4 lower on
|TH350 3-SPEED AUTOMATIC|
||Final Drive Ratio
|TH375/400/475 3-SPEED AUTOMATIC|
||Final Drive Ratio
Why you don't want a 700R4 in your muscle car or truck!
There are good places for a 700R4 and bad places. Fortunately the Gear
Vendors Under/Overdrive can handle all the bad places. High horsepower, heavy car, or heavy
footed driver, and guys who love performance will all go the Gear Vendors route. A 700R4 is
ideally suited to a fuel injected, stock motor, in a light car with a very moderate driver.
This is because that trans is hyper sensitive to throttle cable adjustments on carburated
vehicles so it is really only decent with a computer (4L60E) that typically coincides with a
late model swap. Also the 700R4 has a huge step between each gear and a very tall overdrive
gear that requires a lockup converter (another irritation and failure point) that will have
many motors with a sizable cam and carburetor lugging (besides sounding bogged down and
It is not that the trans isn't decent it is just meant for the astro
vans and gently driven camaros to get good EPA fuel mileage. Imagine you have a little two
seater like a 32 Ford that is scary to go fast in anyways. Simple light little car
that goes fast enough for you the 700R4 is a good cheap alternative to the Gear Vendors.
A Gear Vendors would still be more fun, and outperform and out-last the 700R4 but in this
case the 700R4 is a decent choice.
On the other hand if you have a heavy full bodied car and enjoy performance
through the gears. Maybe even struggle with the idea of having a manual because you like to
shift here the Gear Vendors is the only choice. You get six forward, close, performance
ratios in a bulletproof package that will last you a lifetime of abuse even on the dragstrip.
There is no 700r4 guaranteed for two years of dragstrip use. You put the Gear Vendors behind
a powerglide, TH-350, or TH400 and you have a trans package that stays in the car. The money
you saved on a 700R4 is out the door if you ever have to work on it again. Do the Gear Vendors
and your done with this part of the car.
Check out the Magazine Articles tab and the Racing tab. These race cars
run the same exact product we sell to all our street customers. Get one you will love
it guaranteed or your money back (see warranty for details).
CHEVROLET / GMC Application Guide
2-Wheel Drive 2/3- Speed Automatic
GEAR VENDORS, INC. 1717 North Magnolia Avenue, El Cajon, CA 92020
Toll Free 800-999-9555 Telephone (619) 562-0060 Fax (619) 562-1186