93 4L60E weird issue

[a_kelley]

OK so first shift of the day, put it in drive, shifts to 1st. Once it shifts out of first, it won't usually shift back to first, it will start out in second gear. Manual shift to first works every time.

<40k on a rebuild by a reputable builder
New shift solenoids.
(Trans got contaminated with coolant from a blown trans cooler, flushed since then)
GM digital tech 2 can't force 1-2 solenoid on, but jumping solenoid to ground works.

I'm leaning to blown prom, tried new ecm with original PROM but same results.

What say y'all?

 

[a_kelley]

Maybe clogged screen in valve body feeding the 1-2 valve?

 

[a_kelley]

It was the ecm. Wired a switch to control 1-4 solenoid.. It goes in 1&4 with switch on. Bad ecm, bad.

 

[a_kelley]

Ok so after further testing, 4th consistently engaged with the switch but first gear will generally only engage first time in a run cycle. Broken 1-2 shift valve sitting? Manual 1st works most of the time

 

[a_kelley]

Ok apparently the switch doesn't work all the time so it must be a trans problem.. Any hints from those experienced with 4L60Es?

 

[transman731]

1-2 shift valve is most likely hanging, manual low overrides the shift valve

 

[a_kelley]

Will I need a repair kit (ream and oversize valves spool) or can I just clean up the valve?