PI-0785 Service Bulletin/Repair Instructions

Service Program

Trucks
Mack Trucks, Inc.

Greensboro, NC USA
SB-10044337-5065
Date
Group
No.
Release
Page
5.2012
215
017
01
1(23)
Double Idler Gear Pinning Modification

MP8 US2010
PI0785, Double Idler Gear Pinning Modification

(May 2012)

Mack Trucks has authorized a pinning modification of the double idler gear on certain

EPA2010 emission level vehicles equipped with MACK MP8 engines. The double idler

gear must be pinned on all vehicles involved in this campaign. Before proceeding, verify

campaign eligibility by checking Service Program status in eWarranty.

Before performing this procedure, you must view the Double Idler Gear Pinning

Modification animation. Go to Trucks Dealer Portal, click on SERVICE tab, select “tech

support” in list on left side of page and select “technical videos” to view animation.

Note: When performing this procedure if you encounter any signs of idler gear failure

or the idler bearing nut loose, stop the repair and open an E-Service case. Assign it to

Technical Support and in the Descr./Compl. field put “Idler Gear Campaign Failure”.

Describe the details of the failure and attach pictures of the failure to the case.

Note: Check eWarranty for any open software campaigns and perform update before

releasing the vehicle. If there are no open campaigns, release vehicle after performing

pinning modification.
Parts Required
•

•
21925072 - Fixture Kit

21934132 - Consumable Kit
One Fixture Kit 21925072 was pre-shipped to each Dealer through the essential tool

program. To order additional Fixture Kits, call 877-986-5862.

One Consumable Kit 21934132 was also pre-shipped to each Dealer through the essential

tool program and contains the parts required to perform 5 pinning modifications. To order

additional Consumable Kits, call 877-986-5862. The Consumable Kit can only be shipped

Class 3 (ground freight).
PV729-PI0785
USA53548
Mack Trucks, Inc.

Service Program
Date

5.2012
Group
No.
Release
215
017
01
Procedure

You must read and understand the precautions and guidelines in Service Information,

Function Group 20, "Engine Safety Practices" before performing this procedure. If you

are not properly trained and certified in this procedure, ask your supervisor for training

before you perform it.

1 Apply parking brake and place shift lever in neutral.

2 Remove all cables from ground (negative) battery terminals to prevent personal injury

from electrical shock.

3 Drain coolant from radiator and engine using coolant extractor (2815-2V700 or

85112740). Save coolant.

Note: An alternate method is to connect drain hose (9990649) to drain fitting and drain

coolant. Save the coolant in an appropriate container and cover container to prevent

contaminates from getting in the coolant.

4 Remove passenger seat from the cab.

5 Remove engine cover in the cab.

6 Remove transmission access cover.

7 If necessary, remove the overslung crossmember at the rear of the engine. Note the

orientation of the crossmember for reinstallation.

8 Remove rear engine coolant pipe mounts.

9 Uncouple coolant lines at rear of engine. Clean rear of engine with shop towels and

cleaner adjacent to the flywheel speed sensor and PTO cover. Remove PTO cover

and discard O-ring.
Page

2(23)
Mack Trucks, Inc.

Service Program
Date

5.2012
Group
No.
Release
215
017
01
10 Set up a magnetic stand (9999696) and dial indicator (9999683) on timing gear plate.

Position indicator perpendicular to rear face of double idler gear. Zero indicator.
11 By hand, with moderate force, attempt to move gear back and forth in direction of

measurement. DO NOT USE A PRY BAR. Measure gear movement in three evenly

spaced locations on gear by turning engine with flywheel turning tool (88800014).
•
If gear movement is greater than 0.05 mm (0.002 in) in any position, a possible

nut/gear failure has occurred. Stop the repair and open an E-Service case. Assign it to

Technical Support and in the Descr./Compl. field put “Idler Gear Campaign Failure”.

Describe the details of the failure and attach pictures of the failure to the case.
•
If gear movement is less than or equal to 0.05 mm (0.002 in) in each position,

continue to next step.
12 Remove flywheel turning tool.

13 Reinstall PTO cover with new O-ring (part number 976068) provided in Consumable kit.
Page

3(23)
Mack Trucks, Inc.

Service Program
Date

5.2012
Group
No.
Release
215
017
01
14 Loosely chuck 5/8 x 6 in drill bit provided in Fixture kit into high speed drill. Slide 5/8

in drill stop provided in Fixture kit over drill bit and allow it to rest against chuck. Set

drill protrusion beyond drill stop to 80 ±3 mm (3.125 ±0.125 in) to drill bit shoulder and

tighten chuck securely.
CAUTION

The drill stop must be positioned correctly. If drill stop is not positioned correctly,

severe damage to engine can result.
15 If necessary, remove clamp and bracket securing air compressor discharge line.

16 Disconnect crankshaft speed sensor and clip ties securing harness. Remove crankshaft

speed sensor and discard sensor O-ring. Disconnect EGR valve oil drain hose from

flywheel housing and cover hose opening to prevent contamination.
Page

4(23)
Mack Trucks, Inc.

Service Program
Date

5.2012
Group
No.
Release
215
017
01
17 Install 5/8 inch flywheel housing drill fixture provided in Fixture kit into crankshaft speed

sensor hole. Use M18 hold down bolt provided in Fixture kit in EGR valve oil drain port to

secure drill fixture to flywheel housing. Tighten bolt to 24 ±4 Nm (18 ±3 ft-lb).
5/8 inch Flywheel Drill Fixture and M18 Hold Down Bolt

18 Use chip vacuum (PT2900) or put a crevice tool attachment on a shop vacuum and

position crevice tool over top of drill fixture. Start vacuum.
Page

5(23)
Mack Trucks, Inc.

Service Program
Date

5.2012
Group
No.
Release
215
017
01
Page

6(23)
19 Use light pressure to drill an access hole in flywheel housing. Clean drill flutes repeatedly

by pulling drill back until bit is clear of fixture and then continue into flywheel housing.

Chips should clear freely out of rotating flutes. If chips are becoming packed in flutes,

perform flute cleaning process more often. Position vacuum crevice tool over drill area,

between flywheel housing and fixture, during entire drilling process. Once the drilling is

complete, remove drill and continue to use vacuum to collect any chips that may not

have been picked up previously.
WARNING

When drilling always wear proper eye protection. Failure to wear proper eye protection can result in serious personal injury.
CAUTION

Do not use shop air to blow debris as it could introduce foreign matter into engine and

cause serious engine damage.

Note: The flywheel housing is only approximately 6 mm (0.25 in) thick in the drilling area,

so the drill will penetrate the housing relatively quickly.
Mack Trucks, Inc.

Service Program
Date

5.2012
Group
No.
Release
215
017
01
20 Make sure all visible debris is cleared away from crankshaft speed sensor hole before

removing drill fixture to prevent anything from dropping into flywheel/clutch area. Remove

drill fixture and install EGR valve oil drain hose.
CAUTION

Carefully follow drilling procedure. Failure to properly follow procedure can result in

significant metal debris entry into engine and potential damage including engine failure.

21 Visually inspect gear through access hole to ensure nut is not loose. If nut is loose,

stop the repair and open an E-Service case. Assign it to Technical Support and in the

Descr./Compl. field put “Idler Gear Campaign Failure”. Describe the details of the failure

and attach pictures of the failure to the case.
Page

7(23)
Mack Trucks, Inc.

Service Program
Date

5.2012
Group
No.
Release
215
017
01
22 Chuck 1/4 inch center drill bit provided in Consumable kit into high speed drill. Use

Go/No Go depth gauge provided in Fixture kit to confirm drill protrusion is 69 mm (2.7

in) from collar to drill bit shoulder (white mark on depth gauge). Make sure drill stop

screws are tightened securely.
CAUTION

The drill stop must be positioned correctly. If drill stop is not positioned correctly,

severe damage to engine can result.

Note: The drill stops are pre-assembled with Loctite® to 1/4 inch drill bits. If the drill stop

is not positioned correctly, use heat to break Loctite® loose and reinstall drill stop to

correct depth.
Page

8(23)
Mack Trucks, Inc.

Service Program
Date

5.2012
Group
No.
Release
215
017
01
Go/No Go Depth Gauge

1. Magnet
4. 1/4 inch Center Drill Pilot Hole Depth
2. Two Marks Indicate 13L Gauge
5. Installed Pin Depth
3. 1/4 inch Letter-C Drill Depth
6. Bottom
Page

9(23)
Mack Trucks, Inc.

Service Program
Date

5.2012
Group
No.
Release
215
017
01
23 Check that barrel slides freely in 1/4 inch dowel pin hole drill fixture provided in Fixture

kit. Install fixture into crankshaft speed sensor hole and fasten using speed sensor bolt.

Tighten to 8 ±2 Nm (72 ±12 in-lb). Adjust drill fixture barrel until contact with hub is felt.

Tighten screw to lock barrel in place, do not overtighten. Use a shop towel to cover gap

between drill guide tube and flywheel housing access hole to prevent any debris from

entering engine.
CAUTION

The drill fixture must be properly adjusted for contact against hub. This is critical to

drilling operation. If fixture is not properly adjusted, significant metal debris can enter

engine and cause potential damage including engine failure.
CAUTION

The magnet at the end of the drill fixture barrel is brittle and can break or shatter if tool

is dropped or impacted.
1/4 inch Dowel Pin Drill Fixture
Page

10(23)
Mack Trucks, Inc.

Service Program
Date

5.2012
Group
No.
Release
215
017
01
Page

11(23)
24 Lubricate drill bit tip with oil. Use light pressure to drill pilot hole until contact with drill stop

is made. It is critical to use light drilling pressure to allow bit to cut and not be forced.

Otherwise, drill will walk and result in an inaccurate hole position. Clean drill flutes

frequently by pulling drill back until bit is clear of fixture and then continue cutting. Repeat

as required. Chips should clear freely out of rotating flutes. If chips are becoming packed

in flutes, perform cleaning procedure more frequently.
WARNING

When drilling always wear proper eye protection. Failure to wear proper eye protection can result in serious personal injury.

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