Possible 1-2 Shift Solenoid?

In January I went on a 2,000 mile road trip (mostly freeway) in my 1993 GMC Yukon GT (automatic). Probably 100 miles before I got home, it started doing this thing where it wouldn't shift out of 1st unless I got the RPMs to at least 2500, let off the gas for a second, let it shift, and then I could continue to gas in a new gear. Downshifting was normal. I thought it was my TPS, so I replaced it. Nothing changed, so then I thought maybe it was my ECM. So I replaced my ECM and it still didn't fix it. So I just left it and kept driving it like that till now.
I was towing a trailer this last weekend and realized that I don't have 2nd gear. When I rev it up to 2500, it shifts straight into 3rd and stays in 3rd until I downshift to 1st. This whole time I thought it was going into 2nd because I didn't think about overdrive, but when I was towing I was just in Drive and realized I'm operating in just 1st and 3rd. So I had people tell me it was a bad sunshell. But then I was told since I have reverse that it isn't my sunshell. I'm now thinking it's my 1-2 shift solenoid. If you have any suggestions please tell me!

Nobody has any suggestions?

Connect a proper scan tool, look at transmission operation--codes and data.

Or just stuff in a new shift solenoid, filter, and fluid flush. See what happens. Not scientific, but there's a fair chance you'd get lucky.

You might improve those odds by dropping pan and filter, noting the amount of sediment in the pan and the color of the fluid, and checking the existing shift solenoid(s) with an ohmmeter.

So I checked both solenoids. They both read the same number on the multimeter. Roughly 22ohms- which is a healthy reading. I took out the accumulator and took it apart. The 1-2 spring had snapped in half ! So I ordered a new one and we'll see if that fixes my problem.

I had an issue with the transmission manifold pressure switch on my 93 sierra. It caused issues shifting and I would lose gears. Don't know that the pressure switch is your problem, but might not hurt to replace it while you have the pan dropped. If you replace it you want an ac delco manifold pressure switch. I could only find them on amazon. The off brand ones don't work for very long. I went through 3 off brand ones in about 2000 miles.

Well, changing the broken accumulator spring did nothing. At this point I'm thinking of parking it till I can save my pennies to swap a new tranny in.
Nobody has seemed to have heard of this before. Or else nobody wants to guess wrong.

93 GT said:

Nobody has seemed to have heard of this before. Or else nobody wants to guess wrong.

Click to expand...

What happened with this:

Schurkey said:

Connect a proper scan tool, look at transmission operation--codes and data.

Click to expand...

Did you ever connect a pressure gauge to the test port to see what pressures are in the various gear ranges? Perhaps pressures are available through the data stream on the scan tool.

I'm taking it to a mechanic this upcoming week to have it hooked up and scanned. What does a full diagnostic usually run for price?

Free...in my home shop.

Guessing ~100/hr in a professional shop.