HEAD AS 7C5951 - Caterpillar

TECHNICAL INFORMATION BULLETIN May 25, 2005
Excavators M313C (BDR1-Up)
M315C (BDM1-Up)
M316C (BDX1-Up)
M318C (BEB1-Up, BCZ1-Up)
M322C (BDK1-Up, BDY1-Up)EXCAVATORS
Component Code(s) 3030, 5057, 5058, 5060SUBJECT: M300C WEX Transmission Shift Pressure Event Code (127-3)
PROBLEM:
Caterpillar Engineering has received reports of 188-3823 sensors being replaced due to event code 127-3, "Transmission Shift Pressure Too High". The troubleshooting guide states that the event is caused by electronic or electrical faults in the system. This is not necessarily correct, since the pressure can possibly be too high. This can be caused by internal leakage in the medium pressure swivel 8U-5851. Brake pressure leaks past the seal into the shift signal passage, causing the pressure to climb over the specified maximum of 5700kPa (826PSI). If the sensor is found to be OK after performing the specified troubleshooting procedures, then do not replace the sensor. A separate investigation is underway to determine the root cause of the internal swivel leaks.
A secondary possible root cause is related to pressure building up behind the parking brake check valve internal to the pilot manifold. This condition does not harm either the pilot system, or the transmission, and is being investigated to develop a solution.
SOLUTION:
To check for swivel leaks issues, install a pressure gauge on the transmission shifting port of the transmission, and apply the service brake. If the pressure on the transmission increases while applying the service brake, then it is likely the swivel is leaking internally. If the swivel is leaking internally, then reseal the medium pressure swivel.
Another possible solution is to ensure the pilot pressure is set to the correct specification. The pilot pressure is set using the following procedure:
1. Install a pressure gauge (5000kPa) to the Pilot System Test Port.
2. Rotate 3 turns CCW the adjustment screws of the Pilot Relief Valve and the Medium Pressure-Pressure Reducing Valve.
3. Adjust Engine Speed Dial to 10
4. Adjust the Medium Pressure-Pressure Reducing Valve to 3500+200 kPa.
5. Adjust Engine Speed Dial to 1
6. Adjust the Pilot Relief Valve to 3300+200 kPa.
7. Adjust the Medium Pressure-Pressure Reducing Valve to 3000+200 kPa.
8. Check the Pilot Pressure. It should not increase more than 150kPa when activating the Medium Pressure circuit. If the Pilot Pressure increases more than 150kPa, the 9X-2609 setscrew is possibly not installed behind the pilot manifold P port, or it is leaking.
9. If the setscrew is missing, install a new 9X-2609 setscrew, using Teflon sealant.
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