Hello,
I bought a 98 blazer a few months ago, with a bad transmission. Would not shift to third, would just skip to neutral. I did a complete rebuild on this thing, finding some very burnt 3-4 clutches, and replaced the input drum as it was flaking off aluminum, I guess from the heat. Also replaced all internal electronics - solenoids, PCM, even the wiring harness. and installed a trans cooler as well.

Re-installed the trans, and connected up a line pressure guage to the test port, after reading about line pressure issues. Sure enough the pressure was really low - 60 psi in P,N,D,3,2,1, and 80 in R. After more reading, found a suggestion to disconnect the big green connector to the trans, and when I did that, pressure was good - 160 psi in P,N,D, and 260 psi in R.

So my question is - does this mean the computer is bad? Or should I try that PCM ground fix? Line pressure does not fluctuate when the wiring is plugged in, just steady and low.

Thanks!

 

A little more info, for what its worth - prior to pulling the connector, had a scanner hooked up to it, and no codes found. After pulling the connector and running thru the gears (on jack stands), it did throw several trans related ones - P0740, P1860, and one other. Then when connector re-connected, and codes erased, no new ones were thrown.

 

Did you figure it out. I’ve had the exact same symptoms 1998 Silverado 4x4 loses 4th clutch’s. Low line pressure.

 

Wow long time ago. So in my case, it was because I was checking the line pressure with the wheels in the air. You have to check it with the wheels on the ground, with a load. So when I put it down and drove it around, the line pressures looked good, and the trans shifted fine thru all gears