Chevrolet Silverado / GMC Sierra. Service manual — part 2803

Trailer Brake Control Panel

Trailer Brake DIC Display

Manual Trailer Brake Apply

The Manual Trailer Brake Apply Lever is located on the Trailer Brake Control Panel, and is used
to apply the trailer's electric brakes independent of your vehicle's brakes. This lever is used in the
Trailer Gain Adjustment Procedure to properly adjust the power output to the trailer brakes.
Sliding the lever to the left will apply only the trailer brakes. The power output to the trailer is
indicated in the Trailer Brake Display Page in the DIC. If your vehicle's service brakes are
applied while using the Manual Trailer Brake Apply Lever, the trailer output power will be the
greater of the two.

The trailer and the vehicle's brake lamps will come on when either vehicle braking or manual
trailer brakes are applied.

Trailer Gain Adjustment

Trailer Gain should be set for a specific trailering condition, and must be adjusted any time
vehicle loading, trailer loading or road surface conditions change.

Setting the Trailer Gain properly is needed for the best trailer stopping performance. A trailer
that is over-gained may result in locked trailer brakes. A trailer that is under-gained may result in
not enough trailer braking. Both of these conditions may result in poorer stopping and stability of
the vehicle and trailer.

After the electrical connection is made to a trailer equipped with electric brakes, the TRAILER
CONNECTED message will be momentarily displayed on the DIC. The Trailer Brake Display
Page will appear on the DIC showing TRAILER GAIN and OUTPUT, after all vehicle related
service messages are acknowledged by the driver. The dashed lines in the TRAILER OUTPUT
display signifies a disconnected trailer or TBCM fault condition, and will disappear only when
the TBCM fault condition is not present.

Trailer Gain Adjustment

Adjust trailer gain in 0.5 step increments up to 10 gain setting by using the gain adjustment
+/- buttons on the trailer brake control panel switch. Pressing and holding a gain button will
cause the trailer gain to continuously increment or decrement. To turn the output to the
trailer off, set the gain to zero.

Drive the tow vehicle and trailer combination on a level road surface representative of the
towing condition, and free of traffic at approximately 32-40 km/h (20-25 mph) and fully

2008 Chevrolet Silverado 1500

2008 BRAKES Trailer Brake Controls - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

apply the manual trailer brake apply lever mechanism located on the trailer brake control
panel switch. Adjusting trailer gain at slower speeds may result in an incorrect gain setting.

Adjust the trailer gain to just below the threshold of trailer wheel lock-up. Important trailer
wheel lock-up may not occur if towing a heavily loaded trailer. In this case, adjust the
trailer gain to the highest allowable setting for the towing condition.

Trailer Brake Control Panel

The TBCM system has a control panel with the trailer gain and manual apply switches, and is
located on the instrument panel to the left of the steering column. See Instrument Panel Overview
for more information on location. The control panel and switches allows you to adjust the amount
of output, referred to as trailer gain, available to the electric trailer brakes and allows you to
manually apply the trailer brakes. The Trailer Brake Control Panel, and switches is used along
with the Trailer Brake Display Page on the DIC to adjust and display power output to the trailer
brakes.

Driver Information Indicators and Messages

The following indicators are used to inform the driver of several different factors.

TRAILER CONNECTED

This message will be briefly displayed when a trailer with electric brakes is first connected to the
vehicle. This message will automatically turn off in about ten seconds. The driver can also
acknowledge this message before it automatically turns off

CHECK TRAILER WIRING and TRAILER NOT CONNECTED

This message will be displayed if:

The ITBC system first determines connection to a trailer with electric brakes, and then if the
trailer harness becomes disconnected from the vehicle. If a trailer connection is made
initially and the vehicle or trailer wiring connections is not correct the TRAILER NOT
CONNECTED message will display during key up as if there is no trailer connected. If the
TBCM trailer connection is recognized initially and the disconnect occurs while the vehicle
is stationary, this message will automatically turn off in about thirty seconds. This message
will also turn off if the driver acknowledges this message off or if the trailer harness is re-
connected. If the disconnect occurs while the vehicle is moving, the CHECK TRAILER

IMPORTANT: Re-adjust trailer gain any time tow vehicle and trailer loading or

road surface conditions change or if you notice trailer wheel
lock-up at any time while you are towing.

2008 Chevrolet Silverado 1500

2008 BRAKES Trailer Brake Controls - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

WIRING message will continue until the ignition is turned off. This message will also turn
off if the driver acknowledges this message off or if the trailer harness is re-connected or
repairs completed.

There is an electrical fault in the wiring to the electric trailer brakes. The CHECK
TRAILER WIRING message will continue as long as there is an electrical fault in the trailer
wiring. This message will also turn off if the driver acknowledges this message off. To
determine if the electrical fault is on the vehicle side or trailer side of the trailer wiring
harness connection, do the following:

SERVICE TRAILER BRAKE SYSTEM

This message will be displayed when there is a problem with the TBCM system. If this message
persists over multiple ignition cycles there is problem with the TBCM system. Take your vehicle
to an authorized GM dealer to have the TBCM system diagnosed and repaired.

TRAILER GAIN and OUTPUT Display

This display menu can be accessed by scrolling through the DIC vehicle Information menu, or any
time the trailer gain +/- button is depressed, or the manual trailer brake apply lever is actuated.
The trailer gain display is 0 to 10 in 0.5 step increments, and indicates the current user setting of
the trailer output gain. The trailer output is 0 to 10 bars in 1 bar increments, and indicates the
output power provided to the trailer brakes, relative to the gain setting.

2008 Chevrolet Silverado 1500

2008 BRAKES Trailer Brake Controls - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

2008 TRANSMISSION

Transfer Case - BW 4485-NR3 - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

SPECIFICATIONS

APPROXIMATE FLUID CAPACITIES

FASTENER TIGHTENING SPECIFICATIONS

SEALERS, ADHESIVES, AND LUBRICANTS

COMPONENT LOCATOR

TRANSFER CASE DISASSEMBLED VIEW

Application

Specification

Metric

English

DEXRON®VI GM P/N 88861003 (Canadian P/N
88861004)

1.4 liters

1.5 quarts

Application

Specification

Metric

English

Adapter Studs

10 N.m

89 lb in

Case Bolts

21 N.m

15 lb ft

Drain Plug

25 N.m

18 lb ft

Fill Plug

25 N.m

18 lb ft

Vent

6 N.m

53 lb in

Application

Type of Material

GM Part Number

United

States

Canada

Drain Plug

Pipe Sealant

12346004

10953480

Fill Plug

Pipe Sealant

12346004

10953480

Front Output Shaft Cup Plug

Threadlocker

12345382

10953489

Rear Case Half to Front Case Half

RTV Sealant

12345739

10953541

Transfer Case Fluid

DEXRON®VI

88861003

88861004

Vent

Pipe Sealant

12346004

10953480

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Transfer Case - BW 4485-NR3 - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Transfer Case - BW 4485-NR3 - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado