Jeep Transfer Case: BW 13-39
Borg-Warners 13-39 transfer case was marketed as Quadra-Trac.
It is different from Quadra-Trac found in later models.
The BW 13-39 was only used with an AMC version of the GM TH-400
automatic transmission with a special long 10 spline output.
It is not bolt compatible with any other Jeep transmission. Q-Trac
is a full time four wheel drive system that directs power to the
wheel with the least traction. There is an arrangement similar to
an limited slip differential that splits power between the front and
rear driveshafts. There is a vacuum operated emergency drive switch
the locks the differential within the transfer case, so that power
is sent equally to the front and rear axle. Differential locking
is available for use in low traction situations in high and low
range. Low range (2.57:1) is an optional unit that bolts to
the back of the transfer case. There is a Mile Marker 16%
overdrive gear and chain set available for the Quadra-Trac
that effects high and low range and converts the transfer case for
part time operation.
is an chain driven transfer case with an
aluminum case and it may have the casting number 13-39. The chain
for the Quadra-Trac is known for its short life span. The output
for the front driveshaft and the rear driveshaft is on the passenger
side. The Dana 18 is a good canidate to replace a Quadra-Trac
since the outputs are the same. A transmission swap or conversion
would be required to swap in a Dana 18.
The transfer case in the pictures at the top of the page does not
have a low range. It is a full time single speed unit. The pictures
below show a transfer case with a low range.
Drivers side view of the 13-39 with bolt on low range.
Passenger side view of 13-39 with low range.
View of the BW 13-39 with low range from the back.
It was used in the CJ-7 from 1976 until 1979 and earlier in
other models. It was introduced in the early 70s in full size
Jeep trucks, but it was not used after 1979 in any Jeep trucks.
Last modified Wednesday, 01-Dec-2010 09:13:50 MST
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