TH48-E80 Petroleum Transmission Caterpillar

Note: All transmission control valves, 314-9930, 261-3383, and 261-3378 should be modified per Service Magazine, SEPD1360, "Hydraulic Control Modifications for TH48-E80 Petroleum Transmission and SPF343C Pumper Transmission {3074, 3083, 3167}".

Table 1

TH48-E80 ICM Valve History
Control Group	8 Speed No Warm up Feature		7 Speed with Warm-up Feature
	258-8741		314-9942
Valve Group	261-3372	367-2223	314-9940	367-2233
Serial Numbers	1-845	846-Up	1-845	846-Up
Pressure Control Valve	261-3378	367-2179	261-3378	367-2179
Selector Valve	261-3383	375-5500	314-9930	375-5499
Manifold	261-3377	261-3377	261-3377	261-3377

Note: The valve group for serial numbers 1-845 will be identical to the valve group for serial numbers 846 and up after updating per service magazine SEPD1360.

Note: The valve group was updated to reduce clutch power and energy during the shift and increase shift speed to reduce transmission output speed drop during shifting.

Table 2

Required Tools
Part Number	Description	Qty
198-4240	Digital Pressure Indicator	1

Note: Make sure that the filters and the screens are clean before you test any pressures. Make sure that the oil is at operating temperature before you perform this test.

Show/hide table

Personal injury or death can result from sudden machine movement. Sudden movement of the machine or release of air pressure or oil pressure can cause injury to persons on or near the machine. To help prevent possible injury before testing and adjusting any air system or hydraulic system, perform the procedure in the Testing and Adjusting, "General Information" section.

This test will show the following conditions if the conditions exist:

• The transmission section of the pump is good.

• The relief valve of the selector and pressure control valve is correctly set.

Procedure

Illustration 1	g03029476
(1) Pressure tap for the charging pressure of the transmission

1. Connect 198-4240 Digital Pressure Indicator to the nipple at the pressure tap (1).

2. Start the engine while the parking brakes are engaged. Run the engine at low idle (800 rpm) with the transmission in NEUTRAL. The pressure on the gauge should be a minimum of 2758 kPa (400 psi).

3. Run the engine at medium idle (1300 rpm) with the transmission in NEUTRAL. The pressure on the gauge must be 3254 ± 207 kPa (472 ± 30 psi).

4. Run the engine at the high idle (1900 rpm) with the transmission in NEUTRAL. The pressure on the gauge should be 3400 ± 207 kPa (493 ± 30 psi).

5. When this test is complete, stop the engine and remove the test equipment.

Problem: The oil pressure is too low at low idle and the oil pressure is too low at high idle.

Probable Cause

• Failure of the transmission section of the gear pump

• There are bad seals in a clutch of the transmission. Refer to Testing and Adjusting, "Clutch Pressure For Transmission Hydraulic Control Valve - Test and Adjust".

Problem: The oil pressure is too low at low idle and the oil pressure is correct at high idle.

Illustration 2	g03029518
(2) Relief valve (3) Spacers

Table 3

Chart Of Spacers For The Relief Valve(1)
Pt. No. of the Spacer	Thickness	Change in Pressure
145-0105 Spacer	0.25 mm (0.010 inch)	31 kPa (4.5 psi)
145-0106 Spacer	0.90 mm (0.035 inch)	114 kPa (16.5 psi)
145-0107 Spacer	1.60 mm (0.063 inch)	195 kPa (28 psi)

(1)	Before an adjustment is made, be certain that the valve spring is not weak or broken.

Probable Cause

• The setting of relief valve (2) is too low. Add spacers (3). Refer to Table 3. Adjust the relief valve to the low idle setting.

• There are bad seals in a clutch of the transmission. Refer to Testing and Adjusting, "Clutch Pressure For Transmission Hydraulic Control Valve - Test and Adjust".

Problem: The oil pressure is too high.

Probable Cause

The setting of relief valve (2) is too high. Remove spacers (2). Refer to Table 3. Adjust the relief valve to the low idle setting.