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FixItMan
FixItMan, Master Technician
Category: Car
Satisfied Customers: 17327
Experience:  AA DEGREE AUTOMOTIVE/DIESEL TECH
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I have a 1998 K1500 5.7 engine. My trucks problem is the engine

Customer Question

I have a 1998 K1500 5.7 engine. My trucks problem is the engine rpm under light load at around 50 mph - 75 mph goes up around 75 rpm then down the 75 rpm about every 3 - 4 seconds for ever if no load even when pulling my 3000 lb. boat & trailer and with out it. No service engine light or codes and its been going on for about 2 years.
I'm wondering if it is the Torque Converter locking up and unlocking. Then my 2nd question if it sounds like the problem which part do I replace from the 2 choices "TORQUE CONVERTER CLUTCH SOLENOID VALVE" or the "Torque Converter Clutch Pulse Width Modulation Solenoid Valve"??? Thanks, Phil
Submitted: 4 years ago.
Category: Car
Expert:  FixItMan replied 4 years ago.

FixItMan :

Hello, and thank you for allowing me the opportunity to help you. If I am not online when you are, please allow me time to return. This is a problem with the torque converter clutch in the transmission. Typically if it was a circuit problem then it would set a code for it. If there is no light then typically it is due to a bad torque converter itself. I typically recommend removing the torque converter clutch solenoid and cleaning it out and it's port out to see if it helps. I would also do an ohm test on it. If these things check out and do not help then replace the converter. Do you plan on fixing this yourself?

Customer :

Yes I'll fix it if I end up fixing it. Which valve should I clean or replace? The

Torque Converter Clutch Pulse Width Modulation Solenoid Valve or the

TORQUE CONVERTER CLUTCH LOCKUP SOLENOID VALVE???

FixItMan :

Do you know if you have the 4L60E or the 4L80E transmission.

Customer :

It's the 4L60E

FixItMan :

The pulse width modulation valve is the one that needs to be removed and cleaned out or replaced to see if it helps.