First off, I just want to say that I am STILL excited about the engine rebuild and getting the car back up and running. Since I last wrote, I have gotten the A/C changed over from R12 to 143a, new tires, new alternator, new battery, and new radiator.
I started feeling the car not giving it'* all, sort of a slight tug, or chug, when driving, especially when it went into overdrive. Mind you, it'* 17 years old, so I'm not about to race it. She'* too pretty and elegant for that. Don't get me wrong, she moves when she needs to (sleeper).
So, I took the car into my private mechanic who has been working on GM'* for years, very trusted and reputable, and works for himself. He drove it around with the computer monitoring the trans and how and when it shifts. The computer displays different color lines on the screen for what gear it'* supposed to be in. The first gear line never disappeared when it shifted into second gear, but 2,3 and overdrive did. He said he'* thinking it'* the solenoid. We looked it up online and found out the trans doesn't have solenoids, but rather, simple switches. He talked to his trans guy who also agreed that the trans is sort of between electrical and mechanical. problem is, I'm not EXACTLY sure which trans is used in my car, since it'* at the shop, and, I'm coming up with 3 different kinds. I THINK it'* the old 44oT4 trans.. Which the shop manual is showing is now called the 4T60. I'm also told there are 3 versions of this as well, The 4T60, 4T60E and the 4T60M.
Are you still with me so far? Good , because I'm lost.
The problem is that the switch isn't telling the computer that the trans is now in second gear. When it goes into OD, the computer gets confused, when it'* warm out, and if will start to chug, and then throw the code, causing the SES light to come on. While the light is on, I have no power. It'* like the trans is in limp-home mode and you have to push the gas pedal about half way down to get it to move. you can turn the key off, and back on again and SOMETIMES this will clear the code.. but only if it wants to.
This gets very annoying when I'm out on the highway, in traffic, trying to get home, with the A/C on (Phoenix still has a high of 98 this time of year). If i am going over 50, I can usually turn the key off, and back on again after a second and the light will go out, and the engine will stay on. If it'* below 40 I have to shift into neutral and start the engine, and even that will cause the light to come back on again.
Here'* even info....
I thought that it only did it when I had the A/C on. Not the case. I had the A/C on in August, about 6 am. The light will sometimes come on, but not all the time.
It almost always does it in the afternoon with the A/C on. Very rarely does it NOT do it, and usually up a hill or it can just make the SES light come on at a dead stop in traffic.
If you just get tired of it and let the light stay on, after about 20 minutes the car starts to buck and snort, and there is no way it'* going up a hill, even a small one. Found that out Friday before last when I was driving it out to the mechanics shop.
SO.. If someone could give me some information on this I'd really appreciate it! So far the mechanic, his trans guy, and I have all narrowed it down to the switch inside the trans. That being said we don't want to tear into it until we find the switch, which none of us can find. The trans guy said that he'* almost positive this trans does not have solenoids, but rather simple switches.
Most off of the switches I have found are for solenoids.
Can anyone help?
Thanks

Let me throw some things out there rattling in my head.

440T4 and 4T60 are the same thing, GM just renamed the same transmission.

The switches on the 4T60 simply tell the computer what gear the transmission is in. What code is being thrown exactly? The transmission controls its own shift points. There is however a Torque Converter Clutch that is computer controlled, which locks the input and output of the Torque Converter together when appropriate.

The 4t60e gear selection is computer controlled, by solenoids controlled by the computer.

To further clarify, you should have the 4t60, not the 4t60e. The only computer controlled solenoid should be the TCC solenoid.

That'* what I was told, yes.
As far as the codes. I had to pull them yesterday. Code 27, 28, and 29. I also had a code 42, but I think that was when the PCV valve grommet got sucked into the manifold and the mechanic was nice enough to fish it back out, and replace it with the new grommet.
The problem isn't that, the parts aren't that expensive, and we opted to replace the wiring harness going to the sensors. The problem is that the parts are hard to come by.

http://www.troublecodes.net/gm/88-90_38c/
It seems like all 3 codes can set if 4th gear switch is open at start. No codes reference 1st gear switch from what I can tell.

Were codes cleared after the harness was replaced, and then returned?

Also, if your legwork has already kicked up a part number for the transmission switches, you may want to drop it in ebay just to make sure. Plenty of NOS parts are on there.

The codes were cleared last night, however, no work has been done yet, because there are no parts.

So far, all of the part numbers I have found are for the E. Mine doesn't have an E. :/

One more thing to consider.......whenever I had those multiple codes, many times it turned out to be the ECM....those red, white, and blue ECM'*(connector colors) were famous for failing in the late 80'*, early 90'*....

Sometimes a tap test would help, and sometimes not, even though it was the ECM....just another possibility.....