OEM Aftermarket Ratio
Custom Housings Musclecar Heavy Duty
Light Duty And Passenger High-Performance
OEM (Original Equipment Manufacture)
OEM is used to designate replacement parts which are
sold as dealer parts through Ford, GM, Chrysler, etc. OEM parts are well crafted and
expensive. They are not always the best choice, but sometimes they are the only choice.
Aftermarket parts are replacement parts that are not
manufactured or sold as OEM. This does not mean it is not a quality part; it simply is not
A ratio as it pertains to an automotive application is
most easily explained as the number of turns of the rear or drive wheels in relation to
the number of turns of the engine. Basically , this is governed by a gear set in the rear
axle of the car or truck. If the engine is considered the input and the drive wheel is
considered the output, then the input gear or pinion meshes with the output gear or ring
gear to drive or rotate it. The number of teeth on each gear determines the ratio. For
example: A pinion gear may have 15 teeth that mesh with a ring gear that has 45 teeth;
mathematically (45/15) this yields 3.00 ratio. That means that the engine will turn 3.00
times for each turn of the drive wheel. This is generally thought of as a high or highway
ratio, even though it is low numerically. Common ratios in use today range from 2.29
Positraction is a term that is used in a vague sense,
almost generically; something like asking for a coke when you want a soda (not necessarily
a coca-cola)...in its general interpretation, a posi is a device engineered to rotate or
drive both wheels with the same force (forward or back). As opposed to an open
differential which allows the wheels to turn independently, even without drag in opposite
directions if need be. Open differentials were created to allow an axle to negotiate a
curve; after all, the wheel on the inside of the turn navigates a shorter path than the
wheel on the outside. Otherwise, one wheel would drag or skip along the road if the axle
was a rigid non-flexing unit. If conditions on a road were always perfect (as in dry,
flat, uniform texture, etc.), then an open differential would be all that was needed. Now,
consider dirt roads and potholes: It is easy to see the need for both wheels to drive as
if the axle was rigid. Enter posi units...without getting complicated, the posi acts as a
clutch between the two drive wheels, allowing the wheels to turn independently, but at the
same time exerting a drive force on both. This is helpful on dissimilar surfaces such as
sand, gravel, or mud because if one wheel is slipping, the other can still be counted on
to provide drive force. Otherwise, without that drive force, the vehicle will, of course,
be stuck. There are many different designs of positraction units (some are better than
others); the main difference is the amount of friction (at the tire contact path) required
to cause them to clutch or allow one wheel to turn independently. Off-road, heavy duty
towing and hi-performance vehicles place great demands on traction units.
Custom means "Made To Order"...We can
fabricate a custom housing from scratch or retail a pre-made assembly. A rear end housing
is the shell or case that houses the axles, brakes, differential, gears, and the oil that
keeps it all lubricated. The need for custom housings arises when the original can't fill
the bill, either because of strength, size, parts availability, or all of the above.
Naturally, hi-performance and 4WD off-road vehicles come to mind. Both applications are
hard on original parts. The 9 inch Ford, Dana 60, and 12 Bolt GM are the most commonly
custom-built housings. The 9.0 Ford is popular in both hi-performance and 4WD; it has a
good strength/weight ratio and is used mostly in racing applications where light weight is
important. Also, due to its popularity, there are many aftermarket parts available for it.
The Dana 60 (D60) is the strongest unit of the three. It too, is popular in racing, but
its weight becomes a factor if the extra strength isn't warranted. The D60's forte is 4WD
off-road, bracket race cars, and heavy duty towing applications where extra weight is not
a hindrance. Last, but not least, comes the 12 bolt GM...It is prized for its light weight
and good strength and, since it is custom, it uses stronger axles than the originals which
are considered to be its weak link. It is used in hi-performance and off-road. Each of
these units has good aftermarket and OEM parts availability.
Musclecar is unique in that it is a combination of high
performance and passenger car that was manufactured and sold by the OEM's to the general
public to be used on the nation's streets and highways just like any other car. It is
highly prized by its owners. Some owners want absolutely OEM replacement parts
(restoration) while others want high strength race car units or something in between. We
offer both and have years of experience with these cars. Custom housings, axles, and
differentials are prevalent on the race car end of the spectrum. New brakes help to bring
it all to a halt.
Heavy duty is almost a contradiction of terms; it
includes pick-ups and light trucks up to 1 1/2 ton chassis. These vehicles are actually
light duty trucks as far as trucks are concerned. There is no high performance as such in
this market, but bigger is better in these cases and if the original can't be made to hold
up then a bigger unit is in order. Towing, places greater demands on a differential than
normal, especially when getting off the highway is involved. The most common failure in
heavy duty is parts breakage due to overloading. Ratio changes and positractions are the
most common modifications.
Light Duty And Passenger
This category encompasses fully half of our service
shop repairs. It includes 1/2 ton pick-ups and daily-driven automobiles. The majority of
repairs are necessitated by collision and lack of maintenance. Some customers simply want
positraction or a ratio change. Oil leaks are generally a sign of another problem, but
some can be repaired without incurring further expense. A rear end is like an engine and
transmission; it has bearings, seals, gaskets, and gears and they are all designed by the
manufacturer to last through the warranty with normal service. Then it wears out. Owners
of vehicles in this class usually want to repair their car as cheaply as possible. This is
where aftermarket parts really shine. The labor to install the part is the same, but the
part is sometimes 1/2 the cost of OEM and delivers, in most cases, the same
serviceability. We have a large inventory of aftermarket and OEM parts stocked for this
group and service of this nature usually takes only 1/2 day.
This group covers a wide spectrum of on and off-road
vehicles. Generally assumed to be race cars, this group can include everything from
mud-boggers (4WD) to FUNNY CARS and NASCARS and back to street driven musclecars. We
handle the hi-performance market through both the service shop and our mail order office.
We sponsor several high profile racers in the local area and some who appear on nationally
televised events. Custom housings and axles are prominent here because strength and light
weight are highly prized. Optional ratios are a common installation in drag cars and many
4WD covers many segments of our basic line of services.
In standard repair we do just that; we fix what's wrong with the service parts available.
These can be specified as genuine OEM (dealer parts) at customer request and, although
more expensive, in most cases (not always) these parts are higher quality...SUVS (Sport
Utility Vehicles) and pick-up trucks comprise the majority of these type repairs.
Many customers want to make a ratio change. This
usually involves removing the original ring and pinion (gearset) and replacing it with one
of a higher numerical ratio. An example would be a change in an '85-'90 Chevy 1500 series
pickup which commonly comes with a 3.42 ratio to 4.10 ratio. This change is usually
necessitated by a switch to a taller tire.
Installing positraction is another common request. In
4WD it can be installed in both front and rear, but is generally used in the rear only.
There are many traction units to choose from. The main difference between them is their
ability to withstand the rigors of offroad duty. Strength and expense are proportional
here...another consideration is that as a traction unit becomes stronger for off-road it
becomes less and less streetable.
Custom 3rd members are self-contained
differential units which can be removed and replaced without taking the actual brake and
housing assembly out of the chassis. They are all based on the 9.0 Ford because of its
high-strength/weight characteristics (very popular in racing) and the unsurpassed
interchangeability as compared to other designs. There are myriads of aftermarket parts as
well as a good supply of OEM replacements. This form of differential has been around since
the 1950's and is used in everything from Edsels to Pro-Mod racing machines.
2402 West Cbyo-Lynchbg Rd.
Baytown, TX 77521