|
Reverse
(4.220) |
1st Gear
(3.830) |
2nd Gear
(2.062) |
3rd Gear
(1.436) |
4th
Gear
(1.000) |
5th Gear
(0.838) |
Hi Range |
21:1 |
19:1 |
10:1 |
7:1 |
5:1 |
4:1 |
2.28 |
47:1 |
43:1 |
23:1 |
16:1 |
11:1 |
9:1 |
4.70 |
96:1 |
88:1 |
47:1 |
32:1 |
23:1 |
18:1 |
2.28 & 4.70 |
221:1 |
200:1 |
108:1 |
75:1 |
54:1 |
44:1 |
With my stock tcase gears my crawl ratio
was about 48:1. When I installed the single case with marlin
4:70 gears it went down to 88:1. Now
with the second reduction unit my crawl ratio is now 200:1
with both cases in low range and the tranny in first
gear.
Dual Case Installation
To install the dual Marlin case the first thing we did was
to remove the crossmember and drive shafts. Then we unbolted
and dropped my transfer case out. While we had the case out
of the truck Marlin opened it up and inspected it. All
the parts were in excellent condition and it was
reassembled.
The second reduction core was completely
disassembled and cleaned. Every bit of dirt and grease was
removed. The case looked like factory new. The original
gears and bearings were in good condition and were
reinstalled with new seals. The factory 21 spline (4 cyl)
input gear was replaced with a 23 (V6/Turbo) spline
unit. This
matches the 23 spline shaft size and strength used in the
transmission and rear transfer case. The rebuilt
reduction unit was attached to my transfer case using a new
double bearing adapter plate. This new design provides more
strength and smoother operation than previous designs. New
oil galleys direct more oil into the bearing for greater
life. The process of building the Crawl Box requires a
key-way to be welded on to a shift fork and main shaft to be
pressed apart but is mostly a bolt together affair.
The
dual case unit was test fitted into the truck. A mark
was made on the drive shaft tunnel. The dual case was then
removed. Then a 3.5" hole saw was used to drill
through the floorboard to make room for the added
shifter.
Marlin and his staff looked over the
interior of the truck before starting and agreed the shifter
could be brought up in a factory looking location in the
center console. Due
to the limited space available for the added shifter a
Marlin Crawler short throw adapter was used to reduce the
movement of the rear shifter and minimize the need to trim
more plastic. A hole was cut into the console and the
shifter was cut and offset forward about 1/2" so that
it would come up in just the right place. Marlin regularly
spends a lot of time on this part of the installation. After
seeing several dual case installations he has done in the
past I can see why Marlin is famous for being able to bend
and create all sorts of different shifter arrangements to
fit most any truck's interior. A new factory shift boot was
used to cover the hole in the floor and make a smooth
transition up to the console.
New
low profile magnetic drain plugs were used to help prevent
oil drainage on the trail. I have been running a set of
these in my differentials for about a year now. Since
changing over to them I have not had anymore problems with
the drain plugs being knocked loose by rocks on the trail.
When used on differentials a steel washer should be used.
When used on aluminum transfer cases an aluminum washer
should be used.
Due
to the extra 6.5" length of the second reduction unit
and adapter plate it was necessary to lengthen the front
drive shaft and shorten the rear drive shaft. For best fit I
would recommend taking measurements for the drive shafts
after installing the dual case. For the front drive
shaft I lengthened my Gloeco drive shaft.
For
the rear drive shaft I used a front 1985 drive shaft with
factory CV joint. This drive shaft was lengthened to fit
with heavy wall tubing for extra strength. In some
applications shortening the rear drive shaft may cause
vibrations. A CV joint can reduce vibration problems as long
as the pinion angle is not too much. When my rear leaf
spring mounts were welded on during my coil to leaf spring
conversion I choose to point the pinion a few
degrees below the transfer case output. This way when I
later added the dual case and CV drive shaft the angles
would be correct. Other ways to angle the pinion up a little
include degree shims and longer shackles.
Another
advantage to the CV drive shaft is that it places the large
tubing of the drive shaft up and out of harms way. The
tubing is the drive shafts weakest part and can be bent or
dented when driving through rocks. By mounting the
tubing side nearer the transfer case damage to this tubing
can be limited somewhat. On some trucks it is possible
to remove and reinstall the stock drive shaft backwards and
thus moving the tubing up and out of the way.
On my truck the long front travel and tall
lift combined with moving the transfer case rearward
6.5" causes the front drive shaft to hit the stock
crossmember. To solve this problem normally the
crossmember is normally clearance a little with a
hammer. In my case it would be necessary to cut a
notch and add some steel in order to keep the stock
crossmember.
Operation and Testing
With
a dual case setup you have two transfer case shifters.
The forward shifter operates the "Crawl
Box". This shifter only moves forward and
backward and not in the normal J pattern like a stock
transfer case. It has only 3 positions: Low range,
neutral and high range. As an optional extra, Marlin
offers a lighted shift lever for the Crawl Box. This
light is separate from the 4wd light in the transfer
case. This small green light comes on when the front
Crawl Box is in low range. With all the gear
combinations available it's handy to see at a glance if the
Crawl Box is engaged. The shift light requires a
custom modified shift fork inside the Crawl Box. The lighted
shift lever must be ordered with the dual case. If
ordered at a later time the crawler must be disassembled to
modify the shift fork. The lighted shift lever uses a
factory type switch for reliability.
The
rear shifter operates with a normal J pattern. In my case a
short throw shifter kit was used to reduce the travel of the
shifter. This allowed it to fit in a very tight space and
prevents the transfer case handle from interfering with the
other shifters. This kit consists of a 1" riser
plate and custom made shift lever. By using this
kit the throw length is about 1/2 of what it used to
be. It work well but does require a bit more force to
move the shifters. This kit bolts onto the transfer case
with four bolts and the shifter drops in form the top. The
short throw kit can be made for transmissions,
transfer-cases and Crawl Boxes, anywhere you want a shorter
shifting pattern.
The addition of the extra low gears should
prove helpful on the trail, I look forward to putting it to
the test in coming months.