Specifications

4
Installation of the
upper frame bolt.
(Note the removal of the
shock to access the nut
from the outside.
5
Both sides are in
place and are
ready for the engine
and transmission to
be dropped in. Take
care that the mounts
are positioned so
that they are behind
the crossmember.
6
The engine is bolted in using
the stock GM mounts provided
by Advance Adapters.
7
The double-donut design
provides for greater stability
over stock.
8
The Atlas will bolt in one of the
two rotations on the adapter.
We rotated ours almost flat to give
us optimum ground clearance.
9
The transmission, adapter, and
Atlas are a fairly short combina-
tion with an overall length of 38.1”.
This allows for a 22.5” driveshaft in
the rear and a 31” shaft in the front.
that was purchased to prototype the At-
las II transfer case. Once the bugs were
worked out, the YJ became the platform
for an extreme trail rig. The cradle is
designed to be used when replacing the
stock Jeep transmission with a GM
TH350 or 700R4. Driveshaft modifica-
tions are not usually necessary when
completely replacing a 999 automatic,
AX15 or Peugeot using the adapters and
the stock transfer case. The cradle can
be used with Advance Adapters’ conver-
sion bellhousings to any stock Jeep trans-
mission; however, the stock transfer case
will be relocated and driveshafts will
need to be fabricated. The engine we
used here is a TBI motor from a ‘95
Chevy C1500. We chose this because of
the simplicity of the fuel injection sys-
tem and the great availability of replace-
ment parts. The headers are a tubular
rendition of the old “ram horn” GM cen-
ter dump manifolds. The 700R4 trans-
mission is from JET Performance in Hun-
tington Beach. We chose this automatic
because of the 3.06:1 first gear and
30% overdrive.
The first step is to remove the stock
Jeep drivetrain. The YJ had a 4.2L 6
cylinder and a 999 automatic from the
factory. Stock 4.2L sixes are great
torque motors, but we wanted the added
horsepower of a Chevy V8. The stock
motor mounts must also be removed.
Usually this is made easier by removing
the front clip. The front shocks must
also be removed to gain access to the
inside of the shock tower. This is an ex-
cellent time to inspect for wear on the
bushings or look for seal failure. The
indexing tabs locate a hole in the shock
tower. The lower boss on the cradle
snaps into the lower frame hole. Be sure
that the mounts are positioned behind
the crossmember, or the motor will be
too far forward. Once bolted in, and the
GM mounts on the block, the engine and
transmission are then lowered into the
chassis. An electric fuel pump and block-
off plate are used on all applications due
to the location of the cradle.
The adapters account for the stock
transmission length and usually require
As featured in 4 Wheel Parts Off-Road Adventures, October / November 2000