Procedure to Determine Idler Height {4159} Caterpillar

Track-Type Tractor

D10 (S/N: 84W1-UP; 76X1-UP)

D10N (S/N: 2YD1-UP; 3SK1-UP)

D10R (S/N: 3KR1-UP; AKT1-UP)

D10T (S/N: RJG1-UP)

D10T2 (S/N: RAB1-UP; JJW1-UP)

D11N (S/N: 4HK1-UP; 74Z1-UP)

D11R (S/N: AAF1-UP; 8ZR1-UP; 9TR1-UP; 9XR1-UP; 7PZ1-UP)

D11T (S/N: AMA1-UP; GEB1-UP; TPB1-UP; MDG1-UP; JNS1-UP)

D8L (S/N: 4FB1-UP; 53Y1-UP)

D8N (S/N: 9TC1-UP; 1XJ1-UP; 5TJ1-UP; 7TK1-UP)

D8R (S/N: 7XM1-UP; 9EM1-UP)

D9L (S/N: 14Y1-UP)

D9N (S/N: 1JD1-UP; 6XJ1-UP)

D9R (S/N: ABK1-UP; ACL1-UP; 7TL1-UP; 8BL1-UP; WDM1-UP)

D9T (S/N: TWG1-UP; RJS1-UP; REX1-UP)

Illustration 1	g06220296
(D1) Idler Height

As track roller tread wear and damage, deterioration, or loss of bogie pads occur, excessive machine vibration may result. This vibration is the result of insufficient idler height. Idler height is the distance that the tread of the track idler is above the tread of the adjacent track roller. Refer to Illustration 1 for the area to be measured.

Under typical operating conditions, wear causes the diameter of the track roller treads to decrease at approximately twice the rate of track idlers. When the front or rear rollers reach approximately 70 percent wear, the idler height may approach the minimum recommended value. Variations in operating conditions influence the wear rates. Additionally, the installation of new or rebuilt idlers on machines with partially worn track rollers directly effects idler height. Use the procedure below to measure idler height.

Procedure to Measure Idler Height

1. Move the machine to a hard, level surface. Inspect the machine to make sure that all bogie pads are in place. If any bogie pads are missing or unserviceable, replace the pads.
   Show/hide table

   Illustration 2	g06218384
   Measurement points on a hard surface (D2) Idler Height

2. To check the rear idler height, carefully move the machine in FORWARD until a track shoe grouser is directly below the center of the idler shaft. Refer to Illustration 1.

3. Measure the distance between the bottom of the track shoe grouser in full contact with the surface and the bottom of the track shoe grouser directly below the idler shaft. Refer to Illustration 2.

4. Repeat the procedure of aligning the track shoe grouser directly below the center of the idler shaft on the front idler by carefully moving the machine REVERSE. Measure (D2) for the front idler.

5. Idler height varies from model to model and between front and rear idlers. Compare dimension (D2) with the recommended nominal and minimum values for the front and rear idlers that correspond to your model as shown in Table 1.

Procedure to Shim Bogie Pads

Note: Prior to adding plates under the bogie pads, raise the machine until the bogie pads are hanging free. Carefully support the machine. See the Disassembly and Assembly module in your machine Service Manual for the correct procedure.

Show/hide table

Illustration 3	g06219253
Add plates at point (A)

1. If dimension (D1) is less than the minimum shown in Table 1, plates should be added between the lower bogie pad and the top of the major bogie assemblies at point (A). The appropriate plates and the part numbers for the plates are listed in Table 2. Refer to Illustration 3 for the correct location to add plates.

   Note: The addition of one plate installed under a front or rear bogie pad increases the idler height by approximately 7.50 mm (0.295 inch). To maintain uniform roller loading, an equal number of plates must be installed under the intermediate bogie pads. Take care not to install more plates than are necessary to achieve the proper idler height dimension. Excessive idler height results in poor dozer control, particularly while performing finish dozing operations.