No.: 20 TS-03Rev2
September 2020
TO:

Service Locations

FROM:

Service Systems Development

SUBJECT:

DD Heavy Duty Platform Belt Tensioner Change

ISSUE
A newly designed, dual-arm friction shoe damping tensioner was implemented for the DD Heavy
Duty Platform. New tensioner P/N: A4722001370 was released to engine production on
December 7th, 2018, with approximate engine serial number HDE0644305 for current
USA/Canada and export engines. Belt lengths and maintenance interval per application and
engine variance did NOT change. For current belt information, reference Technical Service
letter 18 TS-4rev. New sections in the appropriate workshop and troubleshooting manuals have
been created. The new sections are labeled “Friction Belt Tensioner”. The tensioner should only
be replaced if indicated by the appropriate troubleshooting manual procedure.
The new friction damping tensioner is not backwards-compatible with certain vehicles
built before November 1, 2017. The new tensioner can be used in all vehicles built on or after
November 1, 2017. Certain vehicles built before November 1, 2017 will use a different
aftermarket friction damping tensioner, part number GT 38667. Refer to Chart 1 for part
numbers.
Note: The new friction damping tensioner, P/N A4722001370 and the aftermarket tensioner,
P/N GT 38667 are not interchangeable. Tensioner GT 38667 should not be used on vehicles
built after November 1, 2017.

Fig. 1, Hydraulic Damping Tensioner

Fig. 2, New Friction Damping Tensioner

Detroit Diesel 13400 Outer Drive, West / Detroit, Michigan 48239-4001

20TS-03Rev2

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9/22/2020

NOTICE:
Selecting the incorrect tensioner may prevent proper installation due to interference
between the tensioner and the fan clutch. This interference may be difficult to identify
visually.
Determine Replacement Tensioner Part Number
Follow the below steps to determine the correct replacement tensioner.

All vehicles built on or after November 1, 2017 should use the Friction Damping
Tensioner. Refer to Chart 1 for part numbers.
For vehicles built prior to November 1, 2017.
1.

Use the VIN to determine if unit is a P4 Cascadia. For Freightliner Trucks, refer to
the 5th and 6th digits in the VIN. HG, HH, HJ, HK, HL, HM, HN, HP, HR, HS, HT, HU
all denote P4 Cascadia.

2.

Refer to Vehicle Info on DTNA Connect to determine the vehicle build date. See
Figures 3 and 4.

Fig. 3, DTNA Connect – Vehicle Info

Fig. 4, Vehicle Info - Build Date

20TS-03Rev2
3.

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9/22/2020

Determine the fan clutch manufacturer by referring to module 273 in PartsPro.
See Figures 5, 6 and 7.

Fig. 5, Determine Fan Clutch Manufacturer

HOR indicates Horton

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9/22/2020

KYS indicates Kysor = “Other”

Fig. 7, “Other” Non-Horton Fan Clutch

4.

Refer to Chart 1 to determine the correct replacement tensioner.

Chart 1: Determine Replacement Tensioner
Vehicle Build
Date

Prior to
November 1,
2017

November 1,
2017 and
newer

Chassis Model

Fan Clutch
Manufacturer
(See PartsPro
BOM 273)

Original
Tensioner

Freightliner P4
Cascadia

All

Hydraulic

Horton

Hydraulic

Other

Hydraulic

All Other Vehicles
(Non P4 Cascadia)

Hydraulic
All

All
Friction
Damping

Replacement Tensioner
Friction Damping Tensioner
Retrofit Kit
P/N A4722001670 1
Aftermarket Friction Damping
Tensioner P/N GT 38667 2
Friction Damping Tensioner
Retrofit Kit
P/N A4722001670 1
Friction Damping Tensioner
Retrofit Kit
P/N A4722001670 1
Friction Damping Tensioner
Service Kit P/N A4722001570 3

1

Retrofit Kit P/N A4722001670 includes shorter mounting bolts that are required when
replacing the hydraulic tensioner with the new friction damping tensioner. Refer to
18SP743 for a complete kit breakdown.
2

The new friction tensioner P/N A4722001370 (contained in kit P/N A4722001570 and
A4722001670) CANNOT be used in this application.
3

Friction Damping Tensioner Service Kit P/N A4722001570 contains all components
required for replacing the friction damping tensioner. The original mounting bolts are to
be re-used on like for like friction damping tensioner swaps. Refer to 18SP736 for a
complete kit breakdown.

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9/22/2020

ADDITIONAL INFO (NEW)
Detroit™ recommends using the new friction damping tensioner, when applicable and
according to Chart 1. The new belt tensioner has been through vigorous testing to optimize
functionality and reliability. The following components have been optimized for the new friction
damping tensioner.

1.
2.
3.
4.

Large damping shoes for longer service life.
Arm casting reinforcement for additional strength and natural frequency modification.
Double labyrinth arms for improved sealing against elements entering damping mechanism.
Pivot shaft welch plugs for additional sealing against elements entering the pivot shaft and
bushing.
5. Pivot shaft-through-bolt to prevent unwanted pivot shaft movement.
6. Larger pulley bearing diameters filled with high performance grease for longer service life.
Fig. 9, Friction Damping Tensioner Enhancement Description

CONTACT INFORMATION
Please contact the Detroit Diesel Customer Support Center at 800-445-1980 or email
[email protected] if you have any questions.