The knock sensor is mounted on one of three locations. It will be on the engine block. I attached a picture of the three locations. Now, the knock sensor is designed to recognize engine detonation. Basically, if there is valve ping, it changes the ignition timing to prevent the ping. Honestly, I do not feel that has anything to do with the transmission. The same with the o2 sensor.
Since the fluid is clean and full, I have a feeling it either has to do with line pressure or the 1-2 shift solenoid is bad. Picture 2 indicates where it is located on a 4L60E Automatic trans.
Here are the directions for checking line pressure on a 4L60E transmission, which I think you have.
Pictures 3 and 4 correlate with this test.
LINE PRESSURE CHECK
1. Prior to beginning line pressure check, check the following:
a. Transmission fluid level.
B. TV cable adjustment.
C. Outside manual linkage.
D. Engine tune.
2. Connect a tachometer to engine and install oil pressure gauge as shown.
3. When checking minimum TV line pressure, apply brakes, then take line pressure readings in gear range and engine RPM indicated in chart.
4. When checking full TV line pressure, tie or hold TV cable to its full extent of travel and apply brakes. Take line pressure readings in gear range and engine RPM indicated in chart.
If you have the 4L80E trans, here are the directions for testing line pressure. Please note the time limitation for the actual test listed in the directions. It requires a scanner and these ones for the OBD1 systems are getting harder to find. Picture 5 correlates with these directions.
LINE PRESSURE CHECK
WARNING:Brakes must be applied at all times during this test to prevent any unexpected vehicle motion. Total test running time should not exceed two minutes, or transmission damage could occur.
1. Connect Tech 1 scan tool or equivalent to vehicle ALDL connector.
2. Connect suitable oil pressure gauge to line pressure tap.
3. Start engine and ensure transmission is at normal operating temperature and fluid level is full.
4. Check for trouble codes and repair if necessary.
5. With gear selector in Park, access "Override Force Motor" test on the scan tool, then increase force motor current in 0.1 amp increments (allowing five seconds for pressure to stabilize) and note pressure reading. Compare results with pressure chart. Line pressure will pulse either high or low every 10 seconds to keep force motor plunger free. This is normal and will not harm transmission.
6. If pressure readings differ greatly from pressure chart or if pressure is not within 35 - 177 psi in drive, park or neutral ranges and 67 - 324 psi in reverse range, refer to "Troubleshooting."
The last picture I attached is the location of the 1-2 shift solenoid for the 4L80E transmission.
Because your truck is a 1/2 ton V6, I feel it has the smaller trans. However, I added info on both. There is one other thing I would like to add. Way back in the day, (1996) there was a technical service bulletin (TSB) that was related to replacement of the shift solenoids. If I recall, it dealt with a rough shift. However, I don't think it was only related to the 1-2 shift. I did a lot of digging and found the TSB. I thought I would add it in case you wanted to read through it. It was related to the 4L80E transmission, which I question you have. The last picture I attached correlates with this TSB.
A/T - Shift Solenoid Update
Vehicle Powertrain Management Transmission Control Systems Actuators and Solenoids - Transmission and Drivetrain Actuators and Solenoids - A/T Shift Solenoid Technical Service Bulletins A/T - Shift Solenoid Update
A/T - SHIFT SOLENOID UPDATE
File In Section: 7 Transmission
Bulletin No: 37-71-48A
Date: November, 1996
Transmission Product Updates
(New Shift Solenoids)
1991-97 Chevrolet and GMC C/K, P, G Models
1991 Chevrolet and GMC R/V Models with HYDRA-MATIC 4L8O-E Transmission (RPO MT1)
This bulletin is being revised to update the part numbers and to include 1995-97 model years. Please discard Corporate Bulletin Number 377148 (Section 7 - Transmission).
Starting August 14, 1996 (Julian date 226) all HYDRA-MATIC 4L80-E transmissions are being built with the new solenoid assemblies. The new solenoids are serviced for all 1991 through 1997 4L80-E applications.
Previous Part New Part Description 10478125 10478132 Valve assembly, 1-2 Shift Solenoid (Black) 10478126 10478133 Valve assembly, 2-3 Shift Solenoid (White)
I hope this is helpful. I realize it is a lot of information. I would have already replaced the 1-2 solenoid, but again, I cannot be 100% sure that is the issue. That is why I am trying to give as much information as I can.
Let me know if any of this helps and if you have other questions.
Images (Click to enlarge)
Sunday, September 30th, 2018 AT 7:49 PM