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Original
article copied off the JP web site in 2001
This
page updated 9/23/17
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The
early ’70s were the years of full-time four-wheel drive –
a time before gas crisis and performance reductions caused
by emissions-control mandates. Dodge, GM, and Ford trucks
were fitted with the New Process 203 full-time unit that used
an open-center differential and a heavy cast-iron case. But
American Motors had a different solution for full-time 4x4s:
a lightweight aluminum transfer case from Borg-Warner.
Unlike
the NP203, AMC’s Borg-Warner 1339 Quadra-Trac transfer case
included a clutch-pack limited-slip center differential for
superior full-time performance, yet like the 203, the differential
could be locked to provide equal power output to the front
and rear for true four-wheel-drive performance. However, the
Quadra-Trac was available without low-range gearing – the
gear-reduction unit was an option that was bolted onto the
backside of the case.
The
Quadra-Trac was an option for ’73-’79 Wagoneers, Cherokees,
and J-series pickups, and it was available in the CJ-7 from
1976 to 1979. In 1980, a new NP207 case was introduced. The
207 was nothing like the Borg-Warner 1339, but fullsize Jeeps
still carried the name Quadra-Trac on the body, and the sales
literature and owner’s manual called it Quadra-Trac as well.
Newer Grand Cherokees also use the Quadra-Trac name, even
though today’s transfer case is not even related to the original
design.
However,
many of the ’73-’79 versions are still on (and off) the road.
And many uninformed people continue to denigrate the original
Quadra-Trac because they don’t know how it works. Even though
it’s a chaindriven, vacuum-actuated case with an optional
low range, it has been used successfully by racers for years.
Rich Severson of Flamingo Racing ran a stock Quadra-Trac in
a CJ-7 for five winning seasons without a single failure.
Severson notes that maintenance included only a thorough cleaning
and replacement of the special fluid and occasional replacement
of the chain. For on-road drivers and trail riders, the Quadra-Trac
can even be converted to part-time operation with a kit from
MileMarker.
Only
four areas of the Quadra-Trac case usually cause problems:
the low-range reduction unit mainshaft and sun gear, the vacuum-operated
shifting mechanism, the limited-slip differential, and the
normal wear of the drivechain. Most repairs can be accomplished
without removing the entire case – simply remove the reduction
unit, then separate the main case halves, leaving the front
half in the vehicle. This allows you to access everything
but the adapter bearing and seals and the front output bearing
and seals, which only occasionally present problems, and don’t
forget that only a special fluid is to be used in the Quadra-Trac
for proper operation of the differential.
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This
section added by
Jubilee Jeeps
I can’t
account for the accuracy of the JP article, but feel it is pretty
good information. The mentioned use of NP207 by AMC Jeep is not
correct for FSJs. The model number is actually NP219 that was also
called QuadraTrac. The part time transfer case also offered beginning
in 1980 is a NP208. The NP207 was actually used in XJs for 1986-87
behind the GM 2.8 litre V6. They are smaller in comparison to the
the QuadraTracs, both BW1339 and NP219.
I have
done just about everything to Jeep BW 1339 QuadraTracs including
replacing chains, repairing shifter mechanisms, installing Milemarker
part time conversion kits and rebuilding the differential with good
used parts from other units. When rebuilding the differential, it
is important to use the same three thrust washers from each side
of the donor if you can. They are slightly cone shaped and can vary
in angle from one unit to another depending on the amount of wear.
Often one or more of them will be scored, but can sometimes be smoothed
out with light sand paper, emery cloth and some elbow grease. They
should have uniform smooth finish. I have tried using a mix of washers
from different differentials and they just don’t seem to last. These
are referred to as clutch plates by Rick P�w�
in the JP article.
Use
the right fluid! Chrysler/Jeep is no longer selling QuadraTrac
Fluid. It was over priced anyway. The cheaper solution TCL-1 by
Crown Automotive from a Crown dealer (BJ’s
Off-Road). It is also possible to mix your own by using a quality
limited slip differential fluid with 30W non-detergent motor oil.
I prefer the real thing when I can get it cheaper. Two years ago
I bought 24 quarts of Mopar Quadratrac fluid for $68 shipped to
my door! When using a Quadratrac with part time conversion, ATF
is the recommended lubricant.
–
January 2011 – These items are no longer available for the
Borg Warner QuadraTrac:
Morse brand replacement chains MileMarker brand vacuum shifter diphragm for the Edrive
note: For QTs that have been converted to part time, the
vacuum shifter selects 2wd/4wd.
Here
are a couple things I have found in the retainer spring hole for
the vacuum shifter on some of our QuadraTracs. The threaded rod
on the left was in our 76 Cherokee. I made the one on the right
to replace the broken spring (pictured) in our 77 Wagoneer and later
found a good spring to use from another spare case we picked up.
The penny is for size comparison:
Case
Sprocket or Differential:
Here
is a cutaway drawing of the QuadraTrac with Mile Marker conversion
taken from the MileMarker part time conversion kit. It gives a good
view of the shifter and shaft retainer spring. It is common to see
the spring missing, bent, broken or replaced by a rod of the same
length.
Breakdown
of QT Components
w/o Low Range Unit:
Breakdown
of the Low Range Unit:
Vacuum
Diagram:
Transmission
Mount Diagram:
Torque
Specs
Other
Helpful QT Links
Hear
a klunk in there? Description of “Stick-Slip”:
http://www.ifsja.org/tech/tcase/slipstik.html
Frank
in Norway has developed a custom manual shifter to replace the
stock vacumn shifter on his 77 Wagoneer. Nice design work! check
the link for more details.
Ethan Brady on R&R details of one of a kind Quadratrac in a
M715:
http://www.bigscaryjeep.com/QT
RnR.html
Peter
Matusov on the MileMarker 16% part time conversion:
http://www.t-r-j.com/Auto/QT/quadratrac.htm
Source
for Parts: BJs
Offroad
The
image below shows what comes with a MileMarker part time conversion
kit without overdrive option. The hub is smaller for the 16% overdrive
and requires a shorter chain.
9/30/03
Quote from JC Jones of CFSJA List
“My
opinion: The BW 1339 Transfer case is the best full time transfer
case ever designed – hands down. The 1339 was actually a military
prototype that was put into civilian production. Awesome design,
very dependable (when correctly cared for), awesome function, etc.
Even the offset design is wonderful, allows a clear path for obstacle
clearance without worrying about slamming a differential. It has
great low range gearing, can handle an incredible amount of torque
and HP. The chain is larger than nearly any other transfer case
chain – equating to a much stronger chain driven case overall.
Let’s
face it, the people with QT problems are dealing with a very old
transfer case, in most cases never rebuilt, probably never had the
fluid changed (read: neglected), and with very high mileage pulling
around a very heavy vehicle.
They
are quiet, have much better gearing than most stock gear driven
cases, have the ability to lock to provide for all the functionality
of a part time case, really don’t draw gas mileage down very much
in comparison to the advantages you have with full time. My QT’s
have gotten me around in situations where a part time case would
have left me with wheels spinning.”
This
is Krista getting the drive shafts hooked back up after the complete
overhaul we did on her 77 Wagoneer QuadraTrac in July 2003:
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The
only transmission used with the Quadra-Trac was the General
Motors TH400 three-speed automatic with a bellhousing pattern
unique to the AMC engines. The tailshaft is the only other
nonstandard GM part – it’s a 10-spline shaft that sticks out
a good foot from the rear of the housing. This shaft drives
the sun gear in the reduction housing, or the drive coupler
in the units without low range. The coarse nature of the 10-spline
shaft wears on itself and the sun gear, causing a loud bang
when it’s shifted into Reverse.
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The
aluminum adapter between the transmission and the transfer
case is also a transmission mount and a tailshaft support.
Notice the large ball-type bearing in the adapter, which is
much stronger than the current offerings of bushings or small
needle bearings. The transmission pattern is standard TH400,
which means a Chevy or a Buick/Olds/Pontiac TH400 can be adapted
to the case using factory parts; only the output shaft of
the transmission needs to be switched to the Quadra-Trac style.
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Lack
of maintenance is what gives the Quadra-Trac its undeserved
reputation. The aluminum case is plenty strong until a bad
chain or other debris gets lodged between the case and the
drive sprocket, which will cause the unit to literally explode.
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The
chain is the only item, other than the fluid, normally replaced
during service. As the chain wears from use, it stretches
to the point of actually jumping over the sprockets during
heavy acceleration. To check the tension of the chain, insert
a screwdriver in the chain-inspection hole at the bottom of
the case after the fluid is drained. Push up on the bottom
of the chain to see how loose it is; if there’s more than
a half inch of slop, the chain should be replaced.
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The
low-range sun gear and mainshaft suffer from the same 10-spline
blues as the transmission output shaft. In this view, the
trans shaft enters the sun gear from the left. It wears out
the sun gear, which in turn wears out the mainshaft sticking
out to the right. At this point, things can get expensive.
At press time, the mainshaft (PN J8122705) goes for $138 at
your local Jeep dealer, and the sun gear (PN J81227708) has
been discontinued.
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The
optional reduction unit offers a 2.57:1 ratio for low range
and bolts onto the back of the case in place of the cover
plate, drive hub, and sleeve. This photo shows two reduction
units and the different styles of shifters. The unit on the
right is actuated by a cable that ran from under the dash
in fullsize Jeeps from 1973 to 1975. The lever and solid-linkage
design shown on the left was used in all low-range-equipped
vehicles from 1976 to 1979. The lever sticks up from the floor
in front of the driver seat to the left of the transmission
hump.
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EDrive
shifter parts
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The
vacuum shifter (A) receives engine vacuum from a glovebox-mounted
vacuum switch labeled “Emergency Drive.” Rotating
the switch applies vacuum to one of two nipples on the shifter,
causing the rod to move in or out. The attached fork (B) slides
a collar on the output shaft, which locks the center differential.
The control diaphragm is no longer available from Jeep, Crown Automotive or MileMarker. They are available at BJ’s Off-Road!
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Inside
the reduction unit is a simple four-pinion planetary reduction
setup, very similar to many late-model transfer cases. A few
Torrington bearings and a large ball bearing in the rear are
all that will wear out, and proper maintenance can keep those
parts in good working order. Disassembly is straightforward
and consists mainly of removing snap rings and a few bolts.
The reduction housing has its own oil supply and needs to
be filled and drained separately from the rest of the case.
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When
the shift cover is off, you can extract the small spring that
secures the vacuum shifter in the case. Note the square rubber
ring that seals the cover. The same sealing method is used
to seal the two case halves together. A complete gasket and
seal kit is available from Crown Automotive through your local
Jeep shop. Many mechanics prefer to use RTV instead of the
rubber sealing rings, but either method is acceptable.
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The
small E-clips that hold the aluminum shift fork on the shaft
must be taken out prior to removal of the aluminum shift fork.
Without the vacuum control, the differential can’t be locked,
or if the case hasn’t been converted to part-time, it can’t
be shifted into four-wheel drive. A broken vacuum control
is a common problem on the trail, but first it must be determined
if vacuum is even getting to the control. A hand vacuum pump
is handy for applying vacuum to the control, but the vehicle
usually needs to be moving a bit so the gear teeth can be
lined up for the shifter to function.
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If
you need to replace your vacuum shifter, you need to watch
out for spring-loaded detent balls that could sail through
the air. Here, the spring has been reinserted and the ball
is about to be put back. A small screwdriver can be used to
depress the ball and the spring as the rod is slid over to
retain them. It’s a good idea to have a small magnet handy
in case you drop the ball into the shift-fork cavity.
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If
the transfer case is going to be removed from the vehicle,
the driveshafts, speedometer cable, vacuum lines, exhaust
bracket, and transmission mounts must be removed. For a chain
replacement or a part-time kit installation, only the rear
half needs to be taken off. You can separate the case halves
by removing the case bolts. Unfortunately, this shift indicator
switch is in the way of one of the bolts and must also be
removed.
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Rugged
simplicity is evident when the case is apart. The drive hub
on the right is one piece, and the differential unit on the
left is a bolt-together unit. The drivechain rides between
the sprockets, which are supported on large, caged, needle
bearings. If you’re replacing the chain, simply clean the
parts, put on a new chain, and bolt it back together. A ratcheting
sound during acceleration is often the chain hopping over
the sprockets, but the differential should be inspected before
the chain is condemned.
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When
the differential is taken apart, you can see the side gears
nestled into the cone gear with the clutch plates on the backside.
The preloaded plates force the tapered cone into the taper
on the diff housing (much like an Auburn axle differential),
creating the limited-slip bias. These pieces were never available
separately from any manufacturer, including Jeep, because
the differential had to be purchased as an assembly. Good
used differentials still command a premium price.
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A
common yet often overlooked Quadra-Trac malady is the inner
splines stripping inside the differential. Here, the side
gear shows splines in good condition, but all the cone gear
splines have been worn away by the front output shaft (arrow).
The output shaft is harder and never wears, but the stripped
splines cause a ratcheting sound on acceleration and will
eventually keep the vehicle from moving unless the Quadra-Trac’s
differential is locked.
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If
the differential is in good shape, simply clean and lube the
clutches and cones with TCL-1 fluid and reassemble it. Note
that the case holes are offset to ensure proper assembly.
The roll pin (arrow) holds the spider gear cross-shaft in
place and must not be left out, which is what almost happened
here. The differential clutches can get sticky due to old
or improper lube, and also from lack of operation. You can
usually eliminate this slip-stick condition by driving in
a few figure eights or by changing the fluid.
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The
Quadra-Trac system needs a special formulation of oil to allow
proper friction between the cones and plates of the differential.
TCL-1 from Crown Automotive is a duplicate of the factory
formula and comes in quart bottles. Two bottles are more than
enough to fill a Quadra-Trac that has the reduction unit installed.
Also remember that there are two separate fill plugs for the
case and the reduction unit, and each must be filled separately.
The fluid is very susceptible to water contamination and should
always be changed after water running or once a year in humid
environs.
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If
the differential is trashed or a part-time conversion is for
you, MileMarker makes a kit that replaces the differential
assembly. A direct-replacement sprocket and a new rear output
shaft come in kit form with simple instructions. The kit is
also available with a smaller sprocket (right), which, when
coupled with a different chain, equates to a 16 percent overdrive
for rigs with low axle gears that need better mileage. The
rear of the case also needs to be taken apart for the new
output shaft installation, but simple handtools are all that’s
needed. After the conversion kit is installed, regular ATF
can be used instead of the TCL-1.
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The
stern “Emergency Drive” label has kept quite a few
drivers from using the unfamiliar glovebox switch. If you
convert the Quadra-Trac to part-time, the kit includes a sticker
to put over this label. The sticker states “two-wheel
drive” on the left side and “four-wheel drive”
on the right. In addition to the vacuum switch, the locking
hubs must be engaged for four-wheel drive to work.
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Even
though most of the hard parts are discontinued, most Quadra-Trac
service items are available. Crown Automotive no longer carries Morse chains, they just carry cheap import chains. These import chains don’t last and we don’t recommend them.
For quality USA made chains and replacement parts go to BJ’s Off-Road They have front and rear output ball
bearings, all four caged needle bearings for the sprockets,
a plastic thrust washer, and a new vacuum-control diaphragm.
The company also supplies the complete gasket and seal kit,
the shift position indicator switch, and the important TCL-1
fluid. Jeep still services the indicator switch, the drivechain,
the vacuum-control switch in the glovebox, the knob, and the
plastic wear pads on the shift fork.
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When
you replace the chain, align the sprockets precisely in their
bores for it all to slip together. If you have three hands,
it makes for an easier time, especially if you’re under the
rig putting the sprockets and chain in the front half of the
case.
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After
the case is clean and has a new gasket (or RTV silicone),
slap the halves back together and tighten the bolts. Because
the case is aluminum, be careful not to cross-thread the fasteners,
and torque them with a torque wrench to spec. The reduction
unit can be installed along with all the other peripherals,
then filled with the correct fluid for your application. Preventative
maintenance will keep your Quadra-Trac functioning for many
more years to come.
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