Transmission Problem

[GM Guy]

Hey Guys, got a major problem with my 95 GP SE with the 4T60E, owned since new.  270k miles and last night without any prior symptoms at all, never a slip or shutter ever, when taking off from a stop all was normal in 1st then felt like it went into 2nd and 3rd very fast, within approx 2 sec, then into 4th and locked the converter immediately upon the shift and sounds like it is grinding gears as if you had a manual and shift into a high gear when moving too slow for the gear.  Here is where it gets even stranger.  Once in 4th it wont downshift, doesn't matter if you pull shifter down to 3-2-1, and won't unlock the converter and engine will majorly shutter and stall when going to slow, if you can stop it, since it is directly engaged and car will quickly speed up with foot off the gas at idle.  Only way to get back to first is to put in neutral then back to drive.  Also tried holding in 1st and will still do this.  Can be going as slow as 10 mph and will do the same thing.  I am assuming it is in 4th, not 3rd as 3rd should free wheel and not direct engage, due to the gear grinding sound and that the converter is locked up due to stalling.  Visual check - Vacuum line to modulator is connected (don't think the modulator would cause this kind of issue), no trans fluid leaking internally at the main electrical connector/plug, just changed fluid 6 weeks ago and fluid was not burned, average metal on the magnet, fluid is full.  No svc engine light.  Speedo is working so the speed sensor should be fine.  Also tried the 2nd gear start switch and still starts in 1st then same scenario.  If it was going into limp mode it should be starting in 2nd and would have 3rd.  Really need some help on this.  Tried numerous searches but nothing about this kind of problem.  

[GM Guy]

Also gave it 5 hours to cool down last night before trying it again and exactly the same symptoms. Just now took it for a ride and the first 5 min of stop and go all was well. Tried second gear start and was normal and turned off. Then pulled shifter down to first but trans didn't hold in first and upshifted into 2nd as if the shifter wasn't in 1st. I know the ECM will upshift if held too long without load but didn't matter. Held in 2nd then shifted to 3rd, normal. Then when put in D problems started after I came to a stop. Started upshifting into 2nd way early then 3rd way early then no 4th. Still no slipping/shuttering on shifts either. Could the selector position switch on the trans case cause havoc on the ECM? Ideas?

Edited February 7, 2013 by GM Guy

[GM Guy]

Anyone have any ideas?

[mitch0537]

Quite simple actually, and the part is only $2.00 online. It's called "TCC screen", exact same thing happen to my 94 olds vert and come to find out, it's quite common for these transmissions and people often confuse it with another problem. The purpose of the TCC screen is to prevent crap from getting into the TCC lock-up passageways AND regulate the pressure into there. Without it, the TCC will lock-up immediately out of first gear and won't unlock until it gets back into first. Changing it is for an advanced knowledge mechanic since you have to remove the side panel AND the shift body AND disassemble the shift body http://www.makcotransmissionparts.com/84016PA.html good luck. I changed mine without removing the transmission, but it is not an easy task still.

[GM Guy]

Thanks mitch0537!!! This explains a lot and that it is actually locking up in 2nd and up! Would be awesome to know how you were able to remove the side pan without removing the trans. Plenty capable, biggest problem is finding time between work and kids, and of course the wife!