Transmission: Vac Line Disconnected Temporarily, Car SLAMMED Into Reverse

1996 Riv, Supercharged 3800

I was taking out the throttle body to clean the IAC and all around the plate, the car kept shutting off when coasting after letting off the throttle intermittently so I figured that was the issue.

After reconnecting with a gasket maker material supposed to be good for all things (Permatex The Right Stuff), it had a high IDLE from a vacuum leak, 2500 RPM. I took it out, redid it, and used my 6th sense instead of following the instructions and it went down to 1300-1500. On the TB there are two 3/8" vac ports I looped together quickly to identify whether or not there was still a leak, and didn't think reconnecting the transmission vac (modulator) line mattered. I decided to put it in gear (in Reverse) to see how much that lowered the RPM and it SLAMMED into R; I immediately shut the car off.

I have everything reconnected, still a high idle. When I shift into reverse it shifts hard, put in OD and driving it never shifts out of 1st gear. ! Have I just toasted the transmission by accidentally not connecting a vac line? !

I haven't tried individual 1, 2 and 3 shifting yet. I feel like I should let the car sit the rest of the night because I know that gasket material is going to take all night to fully set and harden in this colder weather.

HELP

Still have a vac leak this morning.  I have some industrial black tacky-putty I am going to press in all around the TB.  It will certainly hold for a while to keep the vac leak to a minimum while I drive about to get the proper gasket.  As it heats up though it will become more malleable and seal into wherever this leak is.  That will give me some quick feedback on the drive over on whether or not the large vac leak is the problem with the shifts, or if mechanical damage was done.

I watched a video on YouTube of a guy doing a complete 4T60E rebuild, he is clearly a long term transmission specialist.  Video is over 50 minutes and within the first 4 he gets to the Vacuum Modulator and how he's had people come in with the vac line completely disconnected from it. It seemed like he wasn't concerned about it being a cause of damage, but I don't know if their vac leak was as large as mine.  I have noticed over the years the location of a vac leak makes a difference.  The closer to the engine the more exacerbated the idling RPM's are towards being high.

i wonder if your IAC needs reset or replaced?

I tried the reset procedure to no avail.  I have the FSM and saw there was a reset procedure for the 3.8 and a 4.0 engine.  The 3.8 said to:  Key ON, OFF, ON, OFF, START (so that's what I did, several times).  I didn't try the 4.0 (Key to ON for 20 seconds, then start).

As old as the car is I think it stopped working.  I have a performance modification on the car I have been developing for a while now that has a slight vacuum leak (intentionally) through a needle valve so I can control flow and extra power output.  I have altered it over the past several months and I think the IAC finally went out.  I'm going to NAPA to get a Delphi today whether it needs it or not because I am sure this is the original IAC from the factory.  

Even taking off the butyl tape temp solution and putting on the proper gasket it still idled at 1200 RPM in gear.  There's absolutely no way there is a vac leak on it right now and for it to idle that high the IAC has to be toast at this point.  

... although I did remove the TPS and put it back on, I am not sure if I could have messed that up.  I will investigate that further, I just assumed it went right back in without any sort of special procedure.  I had to put it in at the 6 o clock position and rotate it up to 4, I don't remember if that's how it came off though.

The shifts are much better with the idle down to 1200, although it takes more RPM for the shifts to occur.  It's not slamming into R like it did that one time thank God.

.... it was the TPS.  There's a plastic nub inside that broke that keeps it pre-loaded about 15%.  I didn't put it in at 6 o clock and turn it to 4 like I thought, but when I did and drove it a few times for a few key OFF and ON cycles, the idle came back down to 650~ and it shifts normally.  

Now that the IAC is cleaned it's not shutting off when coasting.  I'll still be picking up a new one tomorrow.  If it would have shut off a few different times I was driving a few days ago I would be in a hospital right now with the way people drive around here.  I can't let a faulty $70 part get my car totalled and/or me killed.