Chamberlain 8808CB User Manual
BEFORE YOU BEGIN:
• The trolley must be in down (closed door) position during assembly and
installation. If you have a completely installed garage door opener, the rail/
opener assembly must be taken down. UP and DOWN Limits must be
readjusted after installation.
• Opener hanging brackets will require repositioning and the addition of an
extra bracket for stability due to increased rail length.
Eight-Foot (2.4 m) Rail Extension Kit
Model 8808CB
To prevent possible SERIOUS INJURY or DEATH:
• Disconnect ALL electric and battery power BEFORE performing ANY
service or maintenance.
IF THIS IS A NEW INSTALLATION:
Use the front (header) rail section, belt assembly, and longer emergency
release rope in this kit in place of those packaged with your garage door
opener. Complete the assembly, installation,and adjustment of your opener
according to your owner’s manual,with the exception of adding an additional
hanging bracket for stability.
IF THIS IS AN EXISTING INSTALLATION, CONTINUE AS FOLLOWS:
1. Pull down on the emergency release handle, then disconnect the trolley
from the door arm.
2. Disconnect the rail/opener assembly from the header bracket and
hanging brackets, and place it on the floor.
3. Remove the belt cap retainer from the opener sprocket and set aside.
4. Disconnect the master link from the trolley threaded shaft and belt;
discard (Figure 1).
5. Remove the spring/nut from the trolley and discard.
6. Remove idler pulley assembly and set aside.
7. Remove the belt assembly and discard.
8. Push the trolley back toward the opener. Disconnect the front rail
section by using a screwdriver tip to pry up the outer tab on each side of
the rail, then slide it off the center rail. Discard the front rail (Figure 2).
9. Align the new front rail with the existing rail assembly, keeping the cut
out “window” at the front (header) end. Be sure to keep it right side up:
the idler pulley bolt hole above the window is larger on top of the rail
than on the bottom. Slide the front rail onto the assembly; tabs along
the side will lock into place.
10. As a temporary stop, insert a screwdriver into the hole 10" (25 cm)
from the front end of the rail (Figure 1). Slide the trolley assembly to
this point.
11. Lay the new belt beside the rail. Grasp the end with the hooked trolley
connector and pass approximately 12" (30 cm) of belt through the
window. Keeping the ribbed side toward the rail, and allow it to hang
while you complete the next two steps.
12. Replace the idler pulley, lock washer and nut. Rotate it to be sure it
spins freely. Grease the center if necessary.
13. Locate the rail tab. Use a flathead screwdriver and lift the rail tab until
the tab is vertical (90°) (Figure 2).
14. Pull the belt around the idler pulley and hook the trolley connector into
the retaining slot on the trolley (Figure 1). The ribbed side must contact
the pulley.
15. With the trolley against the screwdriver, dispense the remainder of the
belt along the rail length toward the motor unit and around the sprocket
(Figure 1). The sprocket teeth must engage the belt.
16. Check to make sure the belt is not twisted, then connect it to the flat end
of the trolley threaded shaft with the master link (Figure 1):
• Push pins of master link bar through holes in end of belt and trolley
threaded shaft.
• Push master link cap over pins and past pin notches.
• Slide clip-on spring over cap and onto pin notches until both pins are
securely locked in place.
The garage door MUST be in the fully closed position during
installation.
Figure 1
Trolley
Connector
Retaining
Slot
Master
Link
Threaded
Shaft
Front Rail
Section
Idler Pulley
Retaining
Slot
Trolley
Connector
Figure 2
To remove rail pry both
end tabs of front
rail slightly outward
CORRECT
INCORRECT
Rail Tab
NEW
FRONT RAIL
Idler Bolt hole
(KEEP LARGER
ONE ON TOP)
Rail Tab
Master
Link
17. Insert the trolley threaded shaft through the hole in the trolley. Be sure
Lock Washer 5/16"
Nut 5/16"-18
Bolt 5/16"-18x7/8"
Hanging Bracket (Cross Brace)
Lock Washer 5/16"
Nut 5/16"-18
Lock Washer 5/16"
Nut 5/16"-18
Lock Washer 5/16"
Nut 5/16"-18
Bolt 5/16"-18x7/8"
Hanging Bracket (Cross Brace)
the belt is not twisted, and the ribbed side faces the rail.
18. Hold the belt at the trolley shaft as you thread the spring nut by hand
(Figure 3) onto the shaft until finger tight against the trolley. Do not use
any tools.
19. Remove the screwdriver.
20. Insert a flathead screwdriver tip into one of the nut ring slots and brace
it firmly against the trolley.
21. Tighten the spring trolley nut with an adjustable wrench or a 7/16" open
end wrench about a quarter turn until the spring releases and snaps the
nut ring against the trolley. This sets the spring to optimum belt tension
(Figure 3).
22. Replace the belt cap retainer and complete the re-installation and
adjustment of your opener according to your owner’s manual.
NOTE: Before hanging the opener, an additional hanging bracket is
necessary for stability.
23. Replace the old emergency release rope with the new, longer
replacement rope.
24. Reconnect power.
25. Make adjustments and test the safety reversal system according to the
owner's manual.
ADDING AN ADDITIONAL HANGING BRACKET:
Cut the enclosed hanging bracket (cross brace) to fit across the installed
hanging brackets. Fasten the cross brace to the top and bottom hole of the
hanging brackets using 5/16" -18x7/8" hex bolts, 5/16 lock washers and
5/16" -18 nuts.
Unfinished Ceiling
Structural Supports
Figure 3
Nut Ring Slot
Spring Trolley Nut
Nut Ring
BEFORE
1" (2.5 cm)
Nut Ring
AFTER
1-1/4" (3.18 cm)
To avoid possible SERIOUS INJURY from a falling garage door
opener, fasten it SECURELY to structural supports of the garage.
Concrete anchors MUST be used if installing any brackets into
masonry.
HARDWARE SHOWN ACTUAL SIZE
Finished Ceiling
Structural Supports
Hex Bolt
5/16"-18x7/8"
Hanging Bracket (Cross Brace) Not shown actual size
Nut 5/16"-18
Lock Washer 5/16"
REPLACEMENT PARTS
Part No. Description Qty
183C158-14 Header Rail Extension 1
41A5250-1 8' (2.4 m) Belt Assembly 1
41A3021 Rope 1
4A1008 Master Link Kit 1
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