Belltech 6616 User manual

6612-888 9/05 
A Division of KW AUTOMOTIVE North America, Inc
1
INSTALLATION INSTRUCTIONS
----3300 W. Pontiac Way Clovis, CA 93612 toll free: 1-800-445-3767 web: www.belltech.com----
6612/6616 & 6614/6618
REAR AXLE FLIP-KIT
1999-UP CHEVROLET SILVERADO/GMC SIERRA 1500
Thank you for being selective enough to choose our high quality BELLTECH PRODUCT. We
have spent many hours developing our line of products so that you will receive maximum
performance with minimum difficulty during installation.
Note: Confirm that all of the hardware listed in the parts list is in the kit (Page 8). Do not begin
installation if any part is missing. Read the instructions thoroughly before beginning this
installation.
Warning: DO NOT work under a vehicle supported by only a jack. Place support stands securely under
the vehicle in the manufacturer’s specified locations unless otherwise instructed.
Warning: DO NOT drive vehicle until all work has been completed and checked. Torque all hardware to
values specified.
Reminder: Proper use of safety equipment and eye/face/hand protection is absolutely necessary when
using these tools to perform procedures!
Note: It is very helpful to have an assistant available during installation.
RECOMMENDED TOOLS:
Properly rated floor jack and six (6) support stands
Felt-tipped pen
Wheel chocks
Steel construction square
Die grinder equipped with abrasive cut-off wheel
½” drive torque wrench
Drill motor with ¼” & ½” twist drill bits
Medium weight ball peen hammer
Standard socket wrench set
Metal file
Air powered ½” drive impact wrench
Grinder with abrasive disc
Flat bladed screw driver
Cleaning solvent and rag
C-Clamps
Masking tape
Safety glasses
! It is very helpful to have an assistant available while performing this installation.
SAFETY REMINDER: PROPER USE OF SAFETY EQUIPMENT AND EYE/FACE/HAND
PROTECTION IS ABSOLUTELY NECESSARY WHEN USING THESE TOOLS
TO PERFORM THE FOLLOWING PROCEDURES!
KIT INSTALLATION
As this is a relatively involved installation, we recommend that a qualified mechanic at a properly equipped
facility perform it. We also recommend that the installation be performed on a firm, flat and level surface,
such as seasoned asphalt or concrete. The use of safe and properly maintained equipment is very important!
In order to document any possible irregularities in the factory ride height of your vehicle, please take a few
moments to fill out the Belltech Vehicle Inspection Record included with these instructions. We also
recommend measuring and recording all stock driveline angles prior to installing this kit. This
information may be helpful if vibration problems arise after installation.

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A Division of KW AUTOMOTIVE North America, Inc
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1. FRAME IDENTIFICATION
Be aware that General Motors has produced several different style rear frame modules for GMT800 ½
Ton trucks. It is very important, prior to beginning installation, that you confirm that you have the
correct parts for your vehicle’s frame style. Refer to Diagram A below and Table A to confirm that
you have obtained the correct kit.
Figure A
Table A: Frame style and Flip Kit identification information
Vehicle Year
Dimension “A”
Area B
Belltech Flip Kit P/N
1999
5.0”
Flat without dimple
6612/6614*
Late ’99-2000
5.0”
Dimpled (as shown)
6612/6614*
Late 2000-01
5.25”
Flat without dimple
6616/6618*
* Indicates Extended Cab Model Kit P/N’s only
1. JACKING, SUPPORTING, AND PREPARING THE VEHICLE
a) Block the front wheels of the vehicle with appropriate wheel chocks. Make sure the vehicle’s
transmission is in “Park” (automatic) or 1st gear (manual). Activate the parking brake.
b) Loosen, but DO NOT REMOVE, the rear wheel lug nuts.
c) Using a properly rated floor jack, lift the rear of the vehicle off the ground. Lift the vehicle so
that the rear tires are approximately 6-8 inches off the ground surface.
d) Support the vehicle using four (4) support stands, rated for the vehicle’s weight. The stands
should be positioned, two on each of the frame rails, just forward of the front leaf spring
hangers and just below the rear leaf spring shackle hangers. Prior to lowering the vehicle
onto stands, make sure the supports will securely contact the straight, flat portions of the
frame rails.
! It is very important that the vehicle is properly supported during this installation to prevent frame
damage and personal injury! Make sure that the support stands are properly placed prior to performing
the following procedures.

6612-888 9/05 
A Division of KW AUTOMOTIVE North America, Inc
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e) Slowly lower the vehicle onto the stands and, before placing the vehicle’s weight on them,
again check that they properly and securely contact the frame rails as described above.
Check for possible interference with any lines, wires, or cables.
f) Remove the rear wheels from the vehicle.
SAFETY REMINDER: Check for safe vehicle stability before proceeding under the vehicle to begin the
following procedures. Never work under a vehicle supported by only a jack. Always use properly rated
support stands to support the vehicle.
g) On Step side models, remove the rear inner-fender liners from the vehicle.
h) Using the floor jack located directly below the differential, lift the axle housing just enough to
remove a significant portion of the axle load from the leaf springs. This step is required to
minimize the load applied to frame rails during notching operations. BE CAREFUL NOT TO
LIFT THE VEHICLE OFF OF THE SUPPORT STANDS.
i) Support the axle housing with two (2) additional support stands at this height. Make sure the
support stands securely contact the axle housing tubes so that the axle housing cannot fall
when detached from leaf springs.
j) Remove the rear shock absorbers from the vehicle (Photo 1). Keep the factory hardware for
use during re-assembly.
2. FRAME NOTCH SUPPORT (C-SECTION) INSTALLATION LEFT-HAND
Due to the design of the included Frame Notch Supports (heretofore referred to as “C-sections”), pickup
box removal is not required with this kit. However, some installers may prefer to remove the box to
facilitate access to the frame. If it is decided to remove the vehicle’s bed assembly, please refer to the
appropriate General Motors Service Manual for recommendations regarding Pickup Box Removal
Procedures.
Safety Reminder: Proper use of safety equipment and eye/face/hand protection is absolutely
necessary when performing the following procedures!
a) Working from the LH rear wheel opening, remove the small plastic clip (Photo 2), which secures
the rear brake line and wiring harness to the top of the frame rail. This is accomplished by
removing the small rivet from its’ mounting hole. The clip is located on the top of the LH frame
rail just rearward of the fuel tank. This clip will not be reused.
!To avoid chassis damage, perform the following procedures to only ONE frame rail at a time.
b) Remove the rear brake line bracket from the top of the driver’s side (LH) frame rail (Photo 3) by
removing two hex-head sheet metal screws using a 13mm wrench. The bracket is located
above and just behind the rear axle. To avoid damage, temporarily secure the rear brake line,
bracket and brake hose, away from the frame rail, using zip ties or elastic straps secured to the
rear axle housing or frame cross-member.
c) Remove factory jounce stop by loosening and removing the attachment nut, located within the
frame rail internal support, using a 15mm wrench.
d) Clean frame rail area (Photo 4) with solvent to remove the factory coating. CAUTION: Do not
use flammable solvents around sparks or open flames.
e) Using the supplied steel template, align slot in template with the slot located on the LH frame rail
above and just behind rear axle housing (Photo 5). Also, align the top and bottom edges of the
template parallel with the frame rail edges. Be sure that the arrow is pointing forward (towards
front of truck). If necessary, fasten template to frame rail using clamps.
! It is very important that the template be positioned exactly as shown/described, so that the C-
Section Assembly fits over the frame rail properly. Check for proper alignment PRIOR to cutting
frame! Also, be aware that this template properly aligns the C-Section notch with the axle ONLY WHEN
using the stock leaf springs, hangers, shackles, and other stock components.
f) Using a felt tipped pen, mark the exact shape of the C-Notch opening onto the outside face of
the LH frame rail (Photo 6).

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g) Using a center punch, mark the center location of the 1/4” hole, provided on the template, as
shown (Photo 7). This hole is made so that there will be a round corner at the intersection of
the cuts. This will eliminate the possibility of cracks forming at the intersections of the cuts.
The rear corner of the C-notch cut intersects within the slot; therefore NO hole is required
there.
h) Remove the template. Extend marked lines in places covered by template (Photo 8).
i) Using a steel square, transfer and mark the lower corners of the C-notch opening, perpendicular
to outer face of frame rail, back to underside portion of frame rail (Photo 9). Be sure the lines
are perpendicular (90 degrees) to outer face of frame rail.
j) IMPORTANT NOTE: Gasoline fumes are extremely explosive. Check to make sure the
fuel tank cap is properly installed and secured, and that the fuel tank is fully sealed.
!Check the backside of the frame rail to be sure that all lines, electrical wiring, control cables and other
components are cleared from this area to avoid damaging them in the following steps. Be sure to wear
proper safety protection when using power tools! DO NOT create sparks near flammable or explosive
materials.
k) Using the drill motor equipped with a ¼” drill bit, drill a hole through frame centered on the mark
made above in Step 3g (Photo 10).
l) With the frame properly supported as described above, use the die-grinder equipped with a cut-
off wheel to cut the C-Notch opening along the scribed lines (Photos 11 & 12). Use the forward
¼” hole, drilled in Step 3k above, to form the front C-Notch corner. If required, a reciprocating
saw may be used to cut through the internal OEM jounce-stop re-enforcement.
!Be careful when cutting the frame rail. DO NOT remove any material from the frame rail that is not
shown/described here. Be careful not to damage any lines or other components located behind the frame
rail. Avoid creating any sharp corners or other defects that may cause unnecessary stress-concentrated
areas in the frame rail. Avoid overheating frame rail.
Safety Recommendation: Due to the close proximity of fuel tank to this area, we DO NOT
recommend using a flame-cutting torch or plasma cutter when performing these operations. Also,
excess heat can easily damage the frame rail and other adjoining components.
!Some care should be taken when cutting through the center portion of the C-Notch, as the factory jounce
stop reinforcement bracket is located within the frame rail in this area. Secondary cutting may be required
from the inside of the frame rail to remove any portion of this bracket that might interfere with subsequent
C-Section installation.
m)This Step is required only for vehicles using the 6616/6618 kits as described in Table A. An
additional notch is required in the lower frame rail flange just behind the C-notch cut out in Step
3l.
oWorking from the inside of the frame area, use solvent soaked rag to clean coating
from the inside upper surface of the lower frame flange (Photo 13).
oUsing felt tip pen (or scribe) and tape measure, mark out a line, parallel to rear C-
Notch cut made in Step 3l above, 3 ½” back towards rear of vehicle (Photo 14).
oMark out a line, parallel to inner edge of frame rail flange, 1 ¼” towards inner area of
frame rail (Photo 15). Photo 16 shows the proper notch layout.
oAgain using the die-grinder equipped with cut-off wheel cut the notch as shown.
Photo 17 shows the completed RH cut.
n) Deburr all freshly cut edges using hand file or grinder.
o) Paint all bare metal surfaces and edges to prevent rust.
p) Install the outer C-section shell over the frame rail, aligning C-notch Support portion with the C-
notch cut made in frame rail. Make sure the C-section fits properly over the frame rail and that
all profiles align correctly (Photo 18). Check that the support is properly aligned such that the

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A Division of KW AUTOMOTIVE North America, Inc
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square notch, located in the top surface of the C-section, is evenly aligned with central bed
cross-member (Photo 19).
!It may be necessary to use a soft-faced hammer to position the C-Section shell over frame rail. Make
sure the C-section is properly installed prior to proceeding with following hole-drilling procedures.
q) With the C-section installed tightly against the outside face of frame rail, use the drill motor,
equipped with a 1/2” drill bit, to transfer the nine (9) ½” holes to the frame rail. Use the C-
section holes to locate the drill bit (Photo 20). Use cutting lubricant or light oil to facilitate the
drilling and to extend drill bit life. To prevent movement while drilling, use C-clamps to fix the
C-section shell to the frame rail. Be careful not to damage any lines or other components
located behind the frame rail.
!Be cautious when drilling these holes, as the fuel tank is located directly behind this area (LH
only). While drilling, we highly recommend placing a protective metal plate in the fuel tank area to
prevent puncture and/or other damage.
r) Working from the outside of the frame rail, insert four (4) ½-20 x 1 ¼” (shorter) hex head bolts
with washers into the two most forward and two most rearward holes (Photo 21). Secure these
bolts with washers and locknuts. These four (4) nuts/washers should directly contact the inner
surface of frame rail. Tighten and torque these bolts to 110 lb ft.
!It is important that these shorter, outermost bolts be installed and tightened PRIOR to internal stiffener
installation procedures (below), as the forward holes cannot be accessed after stiffener is in position.
Follow these instructions exactly as the bolt installation sequence is VERY IMPORTANT!
s) Install the kit-supplied urethane jounce stop to the C-notch portion of the C-section shell with
supplied locknut (Photo 22). It may be necessary to bend the rearward ear of the internal
factory jounce stop reinforcement bracket (cut in Step 3l above) forward to clear the
replacement jounce stop stud and nut.
! The jounce stop must be installed PRIOR to stiffener plate installation below.
t) Insert five (5) ½-20 x 3 ½” (longer) hex head bolts with washers, from outside and through the
remaining holes drilled in Step 3q (Photo 23).
u) From the inside of the frame rail, install five (5) tubular spacers over the threaded-ends of these
bolts. Position the brake line and electrical wiring harness so that they route outside of frame
rail and Internal Stiffener. Zip-tie wiring harness to brake line as shown (Photo 24). Be sure
that none of these components are pinched or damaged by the hardware.
v) Locate the LH C-section Internal Stiffener inside the C-section shell so that the five (5) bolts
pass through the appropriate holes and the tubular spacers are located between the frame rail
and internal Stiffener (Photo 25). The tabs on the Stiffener should point towards the inside of
the vehicle, so that they align with the tabs on the C-section shell.
! Make sure the five (5) bolt spacers are sandwiched between the inside portion of frame rail and the C-
section stiffener.
w) Loosely secure the five (5) bolts, installed in Step 3t, with washers and locknuts but DO NOT
TIGHTEN until instructed to below.
x) Adjust the C-section stiffener position until the remaining five (5) holes and tabs align with the
corresponding holes in the C-section shell. It may be necessary to bend some of the stiffener
plate tabs slightly to align with the corresponding tabs of C-section shell. In some cases it may
be necessary to enlarge one or more holes slightly using the die-grinder or round file to achieve
proper alignment.

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A Division of KW AUTOMOTIVE North America, Inc
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y) Install two (2) 3/8-24 x 1 H.H.C.S. (bolts) with washers through the top two forward holes of the
C-section shell and then through the tabs of the Internal Stiffener.
z) Install one (1) 3/8-24 x 1 H.H.C.S. first through the factory rear brake line bracket (removed in
Step 3b), then through the rearward most top bolt hole of the C-section and finally through the
rear Stiffener tab (Photo 26). NOTE: The hole in the OEM bracket might need to be enlarged
slightly using a round file.
aa)Secure the three (3) bolts with washers and locknuts but DO NOT TIGHTEN until instructed to
below.
bb)Install two (2) 3/8-24 x 1 H.H.C.S. through the lower two holes of the C-section shell and then
through the tabs of the Internal Stiffener (Photo 27) from the bottom. Secure with washers and
locknuts but DO NOT TIGHTEN until instructed to below.
cc)Tighten and torque the five (5) ½” bolts and locknuts installed in Step 3t & 3w to 110 lb ft.
dd)Tighten and torque the five (5) 3/8” bolts and locknuts installed in Step 3y, 3z, 3bb, & 3cc to 45
lb ft.
3. FRAME NOTCH SUPPORT (C-SECTION) INSTALLATION RIGHT-HAND
a) Repeat Steps 3a through 3dd for passenger’s side (RH) of vehicle. Note: the brake line and
fuel tank Steps are not applicable for the RH side. Be sure to have the LH side fully installed
prior to beginning RH side C-section installation. The completed installation should appear as
shown (Photo 28).
4. LEAF SPRING REMOVAL AND RE-INSTALLATION
a) With rear axle assembly properly supported, loosen and remove the U-bolt nuts from both
sides of axle. Remove the U-bolts, U-bolt locator plates, and axle clamps from the axle tubes
(Photo 29). These parts will not be reused.
NOTE: Leaf springs may be under tension. Springs under tension store a great amount of
energy. USE CAUTION during the following steps to avoid personal injury and/or damage to
the vehicle. Be careful not to damage the brake hoses and/or driveline while re-locating rear
axle assembly.
b) Using the floor jack, adjust the height of the rear axle housing to remove weight from the leaf
springs to allow for easy removal of the spring and shackle bolts.
c) Loosen and remove the mounting bolts from the front spring hangers and the bottom of the
rear shackles (Photo 30). Loosen, but do not remove, the shackles from the springs.
d) Mark the leaf springs “Left” and “Right”. Also mark each forward spring end with a forward
pointing arrow so that the springs can be properly re-installed into their original
locations.
e) Carefully remove the leaf springs from their mounting locations.
f) Using the floor jack, lift the rear axle assembly so that the leaf springs will fit under it.
g) Place the leaf springs under the axle in the location and orientation removed (Photo 31).
h) Attach the front spring eye into its location in the front spring hanger using the original
hardware. Lift the rear of the leaf springs up so that shackles fit into rear spring hangers.
Attach using original hardware. DO NOT tighten and torque to final specification until
instructed to below.
i) Locate the Belltech axle Adapter Saddles supplied in the kit. Place the Adapter Saddles on top
of the springs with the hole over the head of the spring center bolt. To properly position the
axle, the offset holes MUST be oriented toward the front of the vehicle (Photo 32). Slowly lower
the rear axle assembly down onto the saddles. The ears should fit into the stock spring
perches on the axle tubes (Photo 33). Make sure both ears on each saddle locate completely
into the perches.
j) Install the four (4) new U-bolts, 2 per spring, over the axle tubes on each side of the leaf spring
packs with threaded ends pointing down. Install the new U-bolts plates below the leaf springs;
offset holes forward, so that the U-bolts pass through the appropriate slots (Photo 34). Attach
the U-bolt plates using washers and locknuts. Tighten and torque locknuts to 90 lb ft.

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!The axle adapter saddles have been design to properly position the rear axle pinion shaft relative to the
driveline so that vibrations are eliminated. If driveline vibrations are experienced, take vehicle to driveline
service shop immediately for driveline angle inspection and necessary adjustments. DO NOT drive
vehicles exhibiting driveline vibrations, as U-joint wear could occur prematurely. Be sure to lubricate the
U-joints if deemed necessary.
k) Torque spring front hanger nut to 92 lb ft. Torque shackle to frame bracket and shackle to
spring nuts to 70 lb ft.
5. SHOCK ABSORBER AND EXTENSION INSTALLATION
a) Install Shock Absorber Extensions (P/N 6654) as described in the 6654-888 instructions
(these instructions are included separately).
b) Install the appropriate Belltech Nitro-Dropor Nitro-Activerear shock absorbers using the
original hardware. See the current Belltech Application Guide or contact you nearest Belltech
Dealer for the appropriate part numbers for your application. Tighten and torque hardware to
70 lb ft.
6. BED CROSS-MEMBER C-NOTCH INSTALLATION
a) Install the Bed Cross-member C-notch (P/N 6655) as described in the 6655-888 instructions
(these instructions are included separately).
!The Bed Cross-member C-notch Assembly helps to prevent the center-section of the rear axle housing
from coming in contact with the underside of the bed. It also strengthens the central area of the bed so
that loads can be carried while reducing the possibility of damage occurring to the bed floor.
7. CENTER-CARRIER BEARING RE-LOCATOR INSTALLATION(EXTENDED CAB MODELS ONLY)
!The Center Carrier Bearing Adjuster assembly allows adjustments to be made to both the horizontal and
vertical positions of the center-carrier bearing on Extended Cab models. These adjustments help to
eliminate driveline vibrations.
a) Install and adjust the Center-Carrier Bearing Adjustment Assembly (P/N 4995) as described in
the 4995-888 instructions (these instructions are included separately).
!Due to installation variables and factory manufacturing variances beyond our control, we HIGHLY
RECOMMEND that the driveline angles present in the vehicle after modification be checked and
compared to the driveline angles present before modification and, if necessary, be brought back within
factory specifications. Installation of shims and/or center-carrier bearing adjustments may be required.
8. FINALIZING THE INSTALLATION
a) On Step side models, replace the rear inner-fender liners.
b) Re-install wheels and torque to the Manufacturer’s specifications.
c) Check that all components and fasteners have been properly installed, tightened and torqued.
d) Lift vehicle and remove support stands. Carefully lower vehicle to ground.
e) Check brake hoses, cables and other components for any possible interference.
f) If necessary, check driveline angles as described above.
g) Check for wheel/tire to chassis/body interference.
h) Immediately test-drive the vehicle in a remote location so that you can become accustomed to
the revised driving characteristics and handling. Be aware that the vehicle will handle
substantially different now that it has been lowered.
i) Take the vehicle to a qualified shop for 4-wheel alignment.

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j) Check all of the hardware and re-torque at intervals for the first 10, 100, and 1000 miles.
!The front of the vehicle MUST be lowered accordingly for proper handling and performance and also to
maintain warranty. See the current Belltech Application Guide or contact you nearest Belltech Dealer for
the appropriate part numbers for your application.
Parts List: 6612/6614 & 6616/6618
GMT800 Rear Axle Flip Kit
Part #
Description
Quantity
6612-050
LH C-Section Frame Support (6612/6614 Only)
1
6612-060
RH C-Section Frame Support (6612/6614 Only)
1
6612-055
LH C-Section Stiffener (6612/6614 Only)
1
6612-065
RH C-Section Stiffener (6612/6614 Only)
1
6612-014
C-section Bolt Spacer
10
6612-005
Axle Adapter Saddle
2
6612-015
U-Bolt 5/8-18
4
110505
5/8-18 Locknut
8
110502
5/8” Washer A325
8
6600-010
U-Bolt Plate
2
110424
½-20 x 3 ¾ H.H.C.S. Grade. 8
10
110408
½-20 x 1 ¼ H.H.C.S. Grade. 8
8
110403
½-20 Locknut
18
110660
½” AN Washer
36
110251
3/8-24 x 1 H.H.C.S. Grade. 8
10
110254
3/8-24 Locknut
10
110625
3/8” AN Washer
20
4915-001
Bump Stop
2
9999-975
7” Zip-Tie
2
6654
Shock Extension Assy.
1
4995
C.C.B. Adjuster Assy. (6614 Ext. Cab only)
1
6612-889-1
Installation Template C-section
1
6616-030
C-Section LH (6616/6618 Only)
1
6616-040
C-Section RH (6616/6618 Only)
1
6616-033
C-Section Frame Stiffener LH (6616/6618 Only)
1
6616-043
C-Section Frame Stiffener RH (6616/6618 Only)
1

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