4.70:1 Gear Install

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4.70:1 Gear Kit

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Tools Required:

  • 12mm, 14mm, and 30mm sockets
  • Adjustable wrench
  • Ratchet and Breaker Bar
  • Regular Hammer
  • 3/16 Diameter Pin Punch
  • Snap Ring Pliers
  • 6mm Allen Wrench
  • Gasket Scraper and/or Cleaner
  • Access to a Press
  • Flat Blade Screwdriver
  • Ultra Gray Silicon
  • Bearing Grease or Assembly Lube

Guide Sections:

21 and 23 Spline

21-Spline vs. 23-Spline InputsThe photo to the right shows 21 (left) and 23 (right) spline inputs side by side. Carb and EFI 4cyl Pickup and 4Runners have transmissions with a 21 spline output. V6 and Turbo trucks have transmissions with 23 spline outputs. Both input and output must be the same spline count. For a single transfer case setup choose the gear set that matches the spline count of the transmission you are using. For dual transfer case setup we recommend using stock 2.28 gears in front and 23 spline 4.70 gears in the rear case.

Why mix 21 and 23 spline in the same dual case on 4cyl trucks?

Marlin Crawler Turtle LogoAll 4cyl Toyota trucks have the 21 spline output, except for the Turbo 5sp trucks. Many people run dual transfer case setups with 21 spline inputs in both units of a dual transfer case without problems. An even stronger setup is to put a 23 spline gear set in the rear of a dual transfer case. As the motor power comes out of the transmission, the torque is more than doubled when it goes through the first reduction unit of a dual transfer case. This means that torque going to the rear input of a dual transfer case is about double that of the front. If you purchase your gears and dual adapter at the same time, get the 23 spline dual adapter and 23 spline gear set. Using 23 spline components in the rear of a dual case setup is stronger yet costs the same as 21 spline components. If you use a 23 spline gear set in the rear, you must have a dual adapter with a 23 spline coupler. If you purchased a 21 spline dual adapter, you can replace the coupler in order to use it with 23 spline gears.

Section 1: Parts List and Overview

4.70 Gear Kit Parts List

21 or 23 Spline input gear w/bearing
Low range gear
Counter shaft gear w/bearing
Transmission output seal
Rear output seal
Front output seal w/felt and retainer
Shift fork clip
Drain and fill plug gaskets (2)
Complete gasket set (5 pieces)
Marlin Crawler shift knob

During disassembly and reassembly we refer to different transfer case housing sections by number. The photo below shows each of the covers and its number.

RF1A Gear Drive T/Case Covers

Section 2: Disassembly of Transfer Case

As you take apart your transfer case we recommend you label each part as it is removed.

Step 1
Step 1: Remove 30mm rear nut and flange.
Step 2
Step 2: Remove 7 bolts and cover #4.
Step 3
Step 3: Remove 4WD idler shaft bearing
outer snap ring.
Step 4
Step 4: Remove 10 bolts and cover #3.
Step 5
Step 5: Pull out and remove 2 oil transfer
Step 6
Step 6: Remove front drive idler gear.
Step 7
Step 7: Remove speedo drive gear, lock ball
and oil pump gear. Do not loose ball!
Step 8
Step 8: Remove 63/28N rear main shaft
Step 9
Step 9: Shift into 2WD High. Remove 2WD/4WD
shift fork roll pin with 3/16" pin punch.
Step 10
Step 10: Remove 2WD/4WD shift fork and
shift collar.
Step 11
Step 11: Remove front output hub.
Step 12
Step 12: Remove front output gear.
Step 13
Step 13: Remove (2) 4WD output gear cage
Step 14
Step 14: Remove thrust washer and it's lock
Step 15
Step 15: Remove front output 30mm nut and
flange. Remove 4 bolts. Remove cover #5.
Step 16
Step 16: Remove front output snap ring.
Step 17
Step 17: Remove front drive output gear.
Step 18
Step 18: Remove 4 bolts, remove shifter
base (top shift) or block off-plate (forward
shift) depending on model.
Step 19
Step 19: Remove 4wd light switch (19mm
1989-1995 or 22mm 1979-1983)
Step 20
Step 20: Remove detent plug, ball and
spring from both sides of upper case. Rotate case
on side, then spring and ball will fall out.
Step 21
Step 21: Remove remaining 4 bolts holding
cover #1. Two bolts are located on the front side,
two are on the rear side.
Step 22
Step 22: Remove idler shaft bearing snap
Step 23
Step 23: Remove input shaft bearing snap
Step 24
Step 24: Drive out roll pins from both
shift rails. Pins will fall to bottom of case.
Step 25
Step 25: Slide cover #1 forward and remove.
Retrieve two shift fork roll pins from bottom of
Step 26
Step 26: Remove input gear.
Step 27
Step 27: Remove counter shaft gear.
Step 28
Step 28: Remove pocket bearing from main
Step 29
Step 29: Remove 2wd/4wd shift fork.
Step 30
Step 30: Remove hi/lo shift fork and shift
Step 31
Step 31: Rotate case 90 degrees right, tap
case lightly to remove shift fork interlock pin.
Step 32
Step 32: Remove 4 bolts and main shaft
bearing cover.
Step 33
Step 33: Remove main shaft bearing snap
Step 34
Step 34: Slide cover #2 off of main shaft.
Step 35
Step 35: Remove snap ring from main shaft.
Step 36
Step 36: Remove 6208N main shaft bearing
using press or gear puller.
Step 37
Step 37: Remove thrush washer and lock
Step 38
Step 38: Remove low speed gear from main
Step 39
Step 39: Remove main shaft cage bearing.
Step 40
Step 40: Remove snap rings from input and
counter shaft gears above. The remaining parts
will not be used during reassembly.

Section 3: Reassembly of Transfer Case

Step 41
Step 41: Apply grease main shaft race way.
Install low speed cage bearing.
Step 42
Step 42: Install new 4.70 low speed gear
onto main shaft.
Step 43
Step 43: Apply grease to the ball hole and
insert ball.
Step 44
Step 44: Apply grease to face of low speed
gear as shown above.
Step 45
Step 45: Slide thrust washer over main
shaft until seated onto face of low speed gear.
Line up notch in washer with ball.
Step 46
Step 46: Slide 6308N bearing onto main
shaft. Press bearing until it contacts thrust
washer. Install snap ring onto shaft.
Step 47
Step 47: Slide cover #2 onto main shaft.
Step 48
Step 48: Install bearing retainer and 4
bolts. Torque to 10 ft/lbs.
Step 49
Step 49: Using a grinder or file, remove
inside radius on shift forks(s). The roll pin must
also be ground down to clear the larger 4.70:1 low
speed gear.
Step 50
Step 50: Top shift case only: Using a
grinder, clearance shift block as shown above.
Step 51
Step 51: On 79-83 models only: Replace
C-Clip on 2WD/4WD shift fork.
Step 52
Step 52: Insert roll pin into low range
shift fork. Shaft can go in two ways, install as
shown above.
Step 53
Step 53: Install shift rod, high/low fork
and clutch sleeve.
Step 54
Step 54: Grease pocket bearing inside and
out. Insert bearing into main shaft.
Step 55
Step 55: Grease both idler and counter
shaft bearings as shown.
Step 56
Step 56: Using end mill or hand grinder
clearance case as required to accept new 4.70
counter shaft.
Step 57
Step 57: Place counter shaft and bearing in
clearanced housing. Rotate counter shaft to check
for proper clearance. Gear should not contact
housing when spun.
Step 58
Step 58: Remove counter shaft from cover #1
number and install into cover #2 as shown above.
Step 59
Step 59: Install input gear in main shaft
pocket bearing.
Step 60
Step 60: Remove snap ring from counter
shaft bearing.
Step 61
Step 61: Also remove snap ring from input
gear bearing.
Step 62
Step 62: Sometimes it is necessary to
clearance cover #1 near the input gear as shown.
Test fit to see if this is necessary. Clearance up
to 1/8" as needed.
Step 63
Step 63: 79-83 cases only. Install roll pin
into shift block. Note position of shift block
fingers and shift rod. Assemble as shown above.
Step 64
Step 64: Place new gasket onto cover #2.
Step 65
Step 65: Slide cover #1 onto cover #2.
Carefully tap cover #1 with hammer until cover #1
seats on cover #2.
Step 66
Step 66: Loosely install two bolts on front
of cover #1. Do not tighten yet.
Step 67
Step 67: Loosely install two bolts on back
of cover #1. Do not tighten yet.
Step 68
Step 68: Install snap ring onto input gear
Step 69
Step 69: Install snap ring onto counter
shaft bearing.
Step 70
Step 70: Install inner snap ring onto input
gear bearing.
Step 71
Step 71: Install inner snap ring onto
counter shaft gear bearing. Push shift rod
Step 72
Step 72: Insert interlock pin into either
detent spring hole. (Skip this step if installing
a twin stick) Turn the case on it's side and tap
if needed to get pin into place.
Step 73
Step 73: Make sure the interlock pin is all
the way into position. Here is can be seen and is
not yet in position. Push the pin in until it can
no longer be seen.
Step 74
Step 74: On 85-88 EFI models only, place
pin just far enough into shift block so that you
can pick up the block.
Step 75
Step 75: Use the pin to place shift block
into transfer case. Slide shift rail into shift
Step 76
Step 76: Note position of detent notches on
2wd/4wd shift rail.
Step 77
Step 77: Using a pin punch, drive pin into
Step 78
Step 78: Slide front output gear with
bearing into cover #2.
Step 79
Step 79: Install snap ring around the
outside of the front output gear bearing.
Step 80
Step 80: Lightly press the front output
seal in from the front of housing #5 as shown,
pressing it down about 1/2" beyond the
housing. Then place the felt atop the seal, then
the metal ring atop the felt, and then lightly
press the metal ring until it is flush with the
housing. The metal ring will push against the seal
moving it into position.

Step 81
Step 81: Turn over cover #5 and grease
inside of rubber seal surface.
Step 82
Step 82: Place this gasket onto face of
cover #2.
Step 83
Step 83: Install cover #5 using 4 bolts.
Torque to 10 ft/lbs.
Step 84
Step 84: Apply grease to ball hole on main
shaft and place ball in hole.
Step 85
Step 85: Slide thrust washer onto main
shaft and over ball. Apply grease to face of
thrush washer.
Step 86
Step 86: Apply grease to inside and outside
of both both front drive cage bearings. Slide
bearings onto main shaft.
Step 87
Step 87: Install front transfer drive gear
onto main shaft.
Step 88
Step 88: Apply grease to face of front
transfer drive gear.
Step 89
Step 89: Slide clutch hub onto main shaft.
Step 90
Step 90: Push roll pin into high/low shift
fork just far enough so it will not fall out.
Step 91
Step 91: Install clutch sleeve and shift
fork onto 2wd/4wd shift rail.
Step 92
Step 92: Using a 3/16" pin punch,
drive roll pin into shift fork so that it is flush
with the fork.
Step 93
Step 93: Install original front drive idler
Step 94
Step 94: Install output shaft rear bearing.
Step 95
Step 95: Slide oil pump drive gear onto
main shaft as shown.
Step 96
Step 96: Apply grease to ball hole and
place ball into hole.
Step 97
Step 97: Slide speedo drive gear onto main
Step 98
Step 98: Install oil transfer tubes as
Step 99
Step 99: Place new gasket onto rear of
cover #2.
Step 100
Step 100: Apply grease to cage bearing in
rear of cover #3.
Step 101
Step 101: Install cover #3 onto the back of
cover #2. Be careful to align oil transfer tubes
in the cover. Install 10 bolts into cover #3.
Torque to 29 ft/lbs.
Step 102
Step 102: Install snap ring onto idler
Step 103
Step 103: Place new gasket onto back of
cover #3.
Step 104
Step 104: Remove speedo lock bolts and tab.
Using a screwdriver remove the speedo drive gear
from cover #4.
Step 105
Step 105: Remove old seal and install new
seal into cover #4.
Step 106
Step 106: Install cover #4 onto the back of
cover #3. Install 7 bolts into cover #4. Torque to
29 ft/lbs.
Step 107
Step 107: Apply grease to speedo drive
Step 108
Step 108: Slide speedo drive gear into
cover #4.
Step 109
Step 109: Install speedo gear lock bolt and
tab, torque to 10 ft/lbs.
Step 110
Step 110: With the case on it's side, drop
in one detent ball.
Step 111
Step 111: Now drop in a detent spring after
the ball.
Step 112
Step 112: Apply silicon to the threads of
the detent plug and install. Flip the case over
onto the other side and install the ball, spring
and plug the same way.
Step 113
Step 113: Install 4wd shift light switch
into cover #1.
Step 114
Step 114: Apply silicone to the spines
inside both flanges.
Step 115
Step 115: Install flange. Note, the
silicone will bulge out just a bit. You should see
a slight bulge on each of the splines.
Step 116
Step 116: Install the main shaft nuts and
tighten to 90 ft/lbs. Using punch, drive the stake
nut into the main shaft as shown above. Repeat for
rear flange.
Step 117: Tighten 4 bolts on cover #1 that were left loose in step #66 & 67. Torque to 29 ft/lbs. Replace drain and fill plug washers with ones provided. Install transfer case into truck. Using the rear fill plug, fill transfer case with 80/90W GL5 gear oil. Do not over fill.

Torque Specifications:

8 X 1.25 mm bolts with 12mm head: 10 ft/lbs
10 X 1.25 mm bolts with 14mm head: 29 ft/lbs
30 mm front and rear flange nuts:  90 ft/lbs


Closing Notes:

No brake in is required for 4.70 gears, we do recommend replacing the oil after the first 1,000 miles and every 30,000 miles thereafter. Conventional or synthetic oil may be used. Again, we recommend 80/90W GL5 or equivalent.