Intermittents drive me nuts!
I put a 59 *****'s wagon body on a 2000 Blazer chassis and drivetrain. All original wire harness from the Blazer.
Sometimes it works perfectly, I put it into drive and the transmission engages quietly and smoothly. Starts out in first gear, shifts smoothly through acceleration, Downshifts when I push on the throttle.This usually happens after I have drive it for a while , turn off the engine and start it up again while its still warm. It is a joy to drive when this happens
Other times it starts in second gear. I know this is going to happen because when I put it into drive I get a clunk sound as the transmission engages. When this happens it shifts into 3rd and 4th gear ( i think) through acceleration. It doesn't downshift when I push on the accelerator.
I occasionally get a code for Solenoid A.
I am also getting a code for cylinder 1 misfire. occasionally. I replaced the rotor cap and wires, and it sounds better, but still get occasional misfire.

 

Sorry, I'm not a transmission man. Intermittent is most likely going to be electrical. Solenoid works by PCM grounding the circuit. 12V is supplied through a fuse. See attachment so you can eliminate external electrical issues.

With the 4L60E transmission, it seems you are probably in Failsafe mode (3rd gear starts unless the selector is placed in D2 or D1,then it has second gear starts). In failsafe mode, you will only have [R] [2] [3]. As seen from the shift pattern below, the most frequent cause is a bad 1-2 Shift Solenoid (approx $20 dealer part) under the transmission pan.

Solenoid
Gear 1-2 2-3
---- ---- ----
1st On On
2nd Off On
3rd Off Off
OD On Off

If your misfire is not felt and you have been doing musical PCMs (I think this is the case IIRC), probably you need to do a crank sensor relearn.

Hope this helps

 

Thanks, Les! I really appreciate the help. Your diagrams have been very helpful to me. You are such an asset to the forum!
Looking at the diagram, It makes me wonder if I don't have an intermittent connection to the transmission. I have read elsewhere in this forum that problems with the torque converter clutch solenoid can cause the clanking I am getting when I shift from park to Drive or reverse. Maybe it's just a loose connection of the power red wire going to Solenoid A or in the VCM connector.

Regarding the Misfire. I will do the crank sensor relearn I found instructions for that. Thanks for the tip!
I have been trying to find instructions for adjusting CPM retard but I have been unable to find any that don't involve modifying the distributor or the clamp to be able to turn the distributor. Can you point me in the right direction? Last night I drilled some holes in the old distributor cap so I could view the angle of the spark. Currently, the advance on Cyl 1 is 20 degrees at 1000 rpm. I was going to try experimenting with the modified distributor cap next - but it seems like there should be a better way.

 

Thanks! Glad to help with an interesting project.

Crank sensor relearn can only be done with a capable scan tool. Minimum cost for capable scan tool for this that I know of is for Vident i-link 400.

Cam sensor retard is only changed by turning the distributor (or replacing worn distributor gear or timing chain).

Ignition timing has nothing to do with cam sensor retard since coil is fired from the crank sensor and PCM, independently of the distributor. This is why cam sensor retard is important in correlating ignition timing with rotor position - this helping avoid misfires. When that spark happens the rotor better be pointed properly to route the spark through the distributor.

Yes, I would verify that trans has 12v to solenoids when shift problem is occuring and also that PCM is grounding the other side of the circuit at same time. This would best be done by monitoring the PCM side of the solenoid with a test light hooked to ground. Light should be on until PCM grounds the circuit to energize the solenoid and the test light goes out. If things are electrically ok, I would replace solenoids. Either way, bet that will fix you up.

 

Thanks for the help with this. It turned out to be an intermittent electrical connection at the transmission.- the connector at the wiring harness. I was a little surprised at this because both the transmission internal wiring harness and 2 of the solenoids were new. I had also replaced the connector external to thetransmission. There was some transmission fluid in the connector that may have been causing the problem. I was considering using a dielectric compound in the connector that would exclude transmission fluid in the future, but I was afraid that the seepage might go both ways and the dielectric compound may contaminate the transmission fluid. I would be interested to hear thoughts on this.

 

I dont think there should be any trans fluid seepage into the connector. I would just run it and see if problem occurs again.

 

To report on progress:
It turns out that the electric connector on the transmission was not seated properly. It was not allowing a good connection- the connector was not fully engaged.

I have developed a new problem. Probably of my own making. As mentioned previously in this thread the connector was intermittent. I was driving at approximately 50 MPH and lost all transmitted power to the wheels like the transmission or transfer case went into neutral.

Looking into the problem I learned that either the transmission was shot, or a solenoid was stuck in the wrong position. Hoping that it was the solenoid I removed the pan and re-seated the connector. All of the transmission trouble codes disappeared.
In the process I found that the filter came loose while removing the pan.

To shorten the story, I re-assembled the transmission and refilled the transmission. I fired up the engine. On jack stands the wheels turned for a few minutes as I shifted through the gears, Then the movement slowed and finally stopped.

I think that either the pump has gone out and the fluid has migrated from the Torque Converter or I hope that maybe the filter siphon tube has come out of the receptacle and I just have to reseat it.

I would appreciate your thoughts before I go to the messy job of pulling the pan again. Or maybe it's just time to cut my losses and get a rebuilt transmission.

 

if your trans pump is working, then will squirt out the cooler line whenever the engine is running. You can always point it into a clean bucket. Are you sure transfer case is not in neutral?

 

I wouldn't get squirting fluid under either scenario, right? If the filter is not connected or the pump is out.?

 

Correct. Well, not a heavy steady stream anyways.