Today, with SUVs all the rage, most have 4 wheel
drive optional. (It's standard on Subaru) Even with four wheel
drive, the farthest off road most SUVs travel is to hop a curb at the shopping
mall. Where did it start?
In 1899, Robert Twiver (sp), of Pittsburgh, Pa.
offered an after market retrofit of a driven rear axle mounted on front
with a single king pin, like the the horse drawn buggies. Steering
must have been quite difficult, especially over rough terrain. (See
photos of four wheel drive 1895 Lansing Steam tractor above.
It has single king pin steering. Despite the lack of differentials,
there wasn't a torque steer problem.)
Duplex Power Car, of Charlotte, Mich., offered a
model B, 2 cyl, 14 HP, four wheel drive automobile in 1906. In 1908,
Otto Zacow (sp), and William Bessidy (sp), improved their steamer
with a steerable king pin. In 1909, they produced seven 45
HP, 4 cyl Badger FWD cars at double the cost of 2 WD equivalent.
Walter A. Owen shortened the name to FWD in 1910 and offered trucks to
the army in 1911. FWD is still in business today.
The Rambler Company built the Jeffrey
Quad for WW one. ( later to become Nash Rambler, American Motors and buy
Jeep). So contrary to popular belief, Willys Jeep did not invent
4 wheel drive.
If you wanted 4 WD on your 37 Chevy, You went to
your Chevy dealer and ask for the Silver
Book option from ASAM. If you had a preference for Fords, Marmon-Harrington
offered 4 WD to fit Fords. This was still a few years before Austin-Bantam
built the first WW II Jeep (General Purpose = GP = Jeep). Willys
"Go Devil" engine was finally designated and Willys' then Ford's production
facilities were assigned to build them. One year only, in 1940, Dodge
offered 4 WD on their ton & half trux. It appears to use Marmon-Harrington
axles. Dodge also offered a half ton 4WD and most popular the 3/4
ton command cars for WW II. .
.
The ALCO offered to 35 -36 Chevy owners a
conventional 4WD system with a top heavy stance. Since it's made
by the Alma company, I doubt it is any relation to The American Locomotive
COmpany of same name. .
During WW II Chev and GMC made 4 and 6 WD trux for
the military. They used a special
low pumpkin ratio (6.67) for a top speed of 48 MPH. The
GMC's transfer case had an underdrive hi gear of 1.16 and a Clark 5 speed
overdrive of 0.799 to counteract it. These Clarks bolt on to two
wheel drive Chevys with 5.43 pumpkins for great hiway travel. Click
" RPM" for more details. About 1949 the Silver
Book option used "NAPCO"
on half and 3/4 ton Chevrolets. .
Back to 1937, Below is a page from the Silver
Book. Below that is an ad for ASAM. I imagine with all
gears and no U-joints, it must have sounded like a rock crusher for miles.
Please email me if you would like larger files so you can see every
detail. "<c1937@znet.com>"
For the military GM offered the following: Note the
front axle uses a 5 ball CV joint rather than the 6 ball used on most front
wheel drive cars today.
Note in the Chevrolet transfer case above left,
that a third axle could be attached to the parking brake. There appears
to be provisions for a dog clutch on existing rear output. Neither
has provisions for differential gears. .
The GMC transfer case above right, is conspicuously
missing the front drive unit for 6X6 trux. Since there is no differential
between the two rear axles, all 8 tires must be the same size from the
same manufacturer with the same air pressure and tread ware, if you run
on pavement. This transfer case differs from the Chevys in that Hi
gear is under drive and Low is farther under. It also appears
that if you switched main drive gear #13 and main driven gear #50, you
would achieve a slight Overdrive in Hi. See "RPM"
for
ratios.
The Blitz Buggy below left, was Australia's WW II
Chev. I don't know the source for the drive train but the motor was
1940 Chev, when Australia entered the War. With the COE design, the
driving position was about as cramped as a modern car with console.
The 1927 Tatra had a center tube frame with independent suspension hooked
front and rear. This permitted foot wells and a lower roof line but
a drive shaft hump in the floor. Ferdinand Porsche incorporated this
design into the KDF (VW) and was sued by Ludwig after the war. The
dorsal tail Tatra, below right, sported a Rear engine V-8 and was said
to have killed more Nazi soldiers than the Czech army when they discovered
the Tatra, they had stolen, had severe under steer. (Plows off slick roads).
Please visit < http://www.logicnet.ru/~len/ab/gal.htm
for iron curtain vehicles. .
Thornton Tandem Drive
Thornton also made a 4 wheel drive that was popular with the loggers. Note that like the GMC above, Hi Gear was an under drive on this unit. This means it could not be used in conjunction with ASAM to make a 6 wheel drive 37 Chevrolet. Unlike the GMC, there is a differential between the rear axles.
I saw a 41 Chev/Thornton at an ATHS show
in Spokane. (Photo of business end below:) He had
a 4 speed main transmission, a 4 speed Brownie, 2 speeds in the Thornton
and two 2-speed rear ends with some clever linkage to keep both in the
same gear. With 64 forward speeds, his floor board had a forest of
shift levers protruding forth. Using the gear ratios from the chart
on RPM, here's more math:
2-speed rearend low ratio = 8.22 (times) Thornton "Power Range" =
2.04 (times) Brownie Low = 2.11 [this is 35.39
with main trans in hi. A standard passenger car is 10.9 in Low]
(times) Chev low = 7.22 Equal = 255.7 in lowest gear. The logger
could put his truck in this gear and chop down a tree while he was waiting
for the truck to pass by. .
Note the frame cross member is
up side down to accommodate the higher propeller shaft. This
is vacuum shift on the 2 speed rears and mechanical shift on the Thornton.
The 37 is torque tube while the 41 is hotchkiss.
2 Speed rear ends.
Deviating a bit from 4 WD, Timken and Eaton offered two different approaches to 2-speed axles for 37 Chevys. Chevrolet adopted the Timken style for 1939.
My only criticism of the
Timken above, is that they should have placed the small low gear directly
behind the pinion and a larger hi drive gear could be located on the other
side where it's size wouldn't be limited by the pinion clearance .
The Eaton below is similar to the planetary unit
from Columbia available for Ford passenger cars.
Back to Trux
After reading this page,
you may want to view the numbers on the RPM page.
These are Silver Book
accessories available from private vendors through Chevrolet. View
Accessories.
If you own an
Advance design or Task Force GM truck, Please check the NAPCO website
<http://www.stovebolt.com/napco
If you'd like to see Iron Curtain vehicles
try < http://www.logicnet.ru/~len/ab/gal.htm
And if all else fails, you can
click Back Home.