Downhill Braking:

TM 9-2320-273-10

Your truck is equipped with an retarder system which enables the engine to act as

a brake. The engine retarder should be used for descending grades, in city traffic

or in any situation where slowing is required but excessive use of the service brakes

is not desirable. The engine retarder is most effective between 1750-2000 rpm.

An example of this is wet or icy pavement. The following procedures should be

applied when appropriate:

1. Place the engine retarder switch on the instrument panel in the high position. If less

engine retarding is needed, place the engine switch to the next lower position.

2. Keep the truck in a gear that will allow you to maintain 1,750-2,000 rpm. This will

provide maximum engine braking effect.

3. The engine retarder is very effective on ice, snow or slick roods by selecting a

higher then normal gear for the rood speed This will reduce rpm and provide

lower engine braking. But first try selecting a lower setting with the ENGINE

RETARDER switch. Engagement of differential lockup may also be helpful on slick

surfaces (refer to instructions on using the Interaxle Differential lockup system).

Failure to follow the following downhill driving

procedures may cause you to lose vehicle control

and result in severe injury or death to personnel.

e. Downhill Braking:

1. Proper downhill procedure is to select o gear which will allow the engine with

the engine retarder applied to control truck speed with the engine rpm at or

below 2,000 rpm and service brakes not applied. This means as you approach

a downgrade, progressively select a gear when combined with the engine

retarder will allow you to maintain an engine speed of 1,750-2,000 rpm.

2. As engine speed exceeds 2,000 rpm, use one positive application of the

service brakes to slow the engine speed to 1,650 rpm, replease engine

retarder, downshift one gear and reapply engine retarder Repeat this

procedure until engine speed can be maintained between 1,750-2,000 rpm.

3. In the event engine overspeeds (above 2,100 RPM), make one positive firm

application of the service brakes to slow vehicle speed.

4. In the event transmission overspends (above 2,300 RPM) and total transmission

disengagement, perform the following

(a) Release engine retarder

(b) Upshift

speed and regain control of the vehicle.

5. If the transmission totally disengages from the engine due to a shift being made

with the engine retarder applied and engine speed has returned to low idle

free wheeling, accelerate the engine to re-engage transmission

6. If you experience a total loss of braking due to heat build-up

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