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SUBJECT:

TT7400EN, Rev. A
April, 2014
Page 1 of 2

Vehicle Acceleration Control on Freightliner Vehicles

MODELS AFFECTED:

Freightliner Vehicles with 2000/3000/4000 Series Transmissions with 5th Generation
Controls

Description of Complaint:
Customers may experience low power on acceleration with Freightliner Vehicles using 2000/3000/4000 Series
Transmissions with 5th Gen Controls.

Background:
Vehicle Acceleration Control (VAC) is an engine management function where the TCM manages engine torque
to limit vehicle acceleration to a calibrated rate. In order to reduce fuel consumption, DTNA/Allison decided to
introduce VAC in the early part of this year as a means of limiting unnecessary acceleration during light vehicle
operation. Five levels of settings were made available with the new 5th Gen Controls calibrations (refer to Table 1).
Table 1. VAC Level Settings
VAC Level

Description

Acceleration Rate
(mph/sec)

Comments
Provides the slowest
acceleration rate. Offers
the highest potential for fuel
savings

5

Ultra Economy

2.2

4

Super Economy

2.6

3

High Economy

3.5

2

Intermediate Economy

4.5

1

Base Economy

0

Off

5.6

Provides acceleration
closest to normal vehicle
acceleration. Offers the
lowest potential for fuel
savings.

Each VAC level uses an acceleration profile that the vehicle tries to follow when accelerating. Base Economy
means that very little limiting will be performed. The vehicle will accelerate similarly to a truck without VAC enabled,
and will have the lowest potential for fuel savings. Ultra Economy means that a large amount of limiting will be
performed. The vehicle will experience the highest amount of torque and acceleration control and achieve the
highest potential for fuel savings.
BRD

424554

Copyright © 2014 Allison Transmission, Inc. All Rights Reserved.

TT7400EN, Rev. A
April, 2014
Page 2 of 2
A number of vehicles built at DTNA Truck Plants during the first weeks of July were programmed with VAC set to
Ultra Economy (Level 5) and High Economy (Level 3). Based on the current engineering guidelines established
by DTNA for VAC, the level should be set to Base Economy (Level 1).

Service Procedure:
Connect the Universal Allison DOC® and access Reprogramming tab. Under Customer Modifiable Constants,
scroll down to Group VAC and adjust Vehicle Acceleration Control to Base Economy (Level 1). When VAC level is
changed, click on Reprogram TCM and process will be complete.
With Universal Allison DOC® still connected to vehicle, verify VAC level change by viewing Customer Modifiable
Constants.
NOTE: The Distributor/Dealer is instructed to adjust VAC settings only.

NOTE: If an engine warning light is set during this procedure, it will be eliminated by starting the engine 5
or 6 times.

Claim Submittal Information:
Allison Service Outlets shall submit a Claim Type 8 on each vehicle completed for labor. Vehicle Identification
Number (VIN) required on claim.
8

Claim Type
Special Activity Indicator
Primary Failed Part

DTNAVAC
70

Complaint Code

AT02

Failure Code

CC03

Labor OP

Labor Hours

Labor Operation

00096501

1

TCM Recalibration

NOTE: Labor not to exceed 1.0 hour labor. The labor time of 1 hour is the maximum allowed to reprogram
the VAC settings addressed above and covers all necessary processing. Additional customer setting
requests will not be covered by this program and will be at the customer’s expense.

NOTE: The issue outlined in this document is not an Allison Transmission, Inc. defect in material or
workmanship.
Reference: Daimler Trucks North America LLC Campaign letter #FSPR 23206

Copyright © 2014 Allison Transmission, Inc. All Rights Reserved.