This is my first how to so be gentle.
The job isn't the hardest to do but it isn't the easiest either.
***Word of Note*** For those of you with 1999 and earlier 1G's, apparently the shift solenoid has an updated design that was used for 2000 and later vehicles. There is information in the box that comes with the new OEM solenoid (cost me $210 at the dealer). I suggest you read it before you take anything apart. This didn't pertain to me so I didn't really pay attention to it. I still have the info at home so I can edit and add it later.
Tools I used:
Metric socket set (just about every bolt was metric except for the speed sensor itself I think I used 8 and 10mm)
Small flat head screwdriver (used to remove connector from speed sensor)
Either a pry bar or a large socket wrench (used to break the shift solenoid loose)
LOTS of rags
oil pan or something else to attempt to catch transmission fluid (was about a quart for me)
Location of Speed Sensor:
Standing at the front of the engine on the drivers side, look down between the black box (TCM?) which is mounted to the left of the fuse box and the actual engine itself. You'll see a connector sticking out of the transmission. The easiest way to find it is to follow the dip stick down. The speed sensor is to the left of the dip stick where it meets the transmission.
Location of the Shift Solenoid:
It's directly below the Speed Sensor. You will actually need to remove the Speed Sensor to get to the middle bolt of the shift solenoid. There are 3 bolts total.
Of course, remove power to the car. I just removed the negative battery connection to the terminal.
Learn from my mistake. The first thing you should do is get some degreaser and spray it between the shift solenoid and the transmission, then hose it down with as much pressure as you can get from your hose (within reason of course). A whole lot of dirt and gravel and stuff gets caught up here and you do not want this going into the open space after you remove the shift solenoid as it will have a good chance of making its way into your transmission. Remove the three screws keeping the...what I think is the TCM attached to the side of the fuse box. It will have one large connector on it, which keeps it connected using a screw. After you remove the 3 screws keeping it attached, remove the large connector by loosening the screw keeping it attached. This screw stays in the connector and does not fall out. Or at least it didn't with me. Move the connector out of the way. Below that you will find another connector with a screw right on the top. Loosen that and remove that connector. That is the connector that connects right into the shift solenoid. Move that aside. Remove the connector attached to the speed solenoid using a flat head screwdriver and applying as little force as possible to remove the connector. You do not want to break the clip. Remove the speed sensor. I used a very large socket to do this. If you have a deep well big enough you might want to use that. I didn't have one and had clearance issues because of a coolant hose that is right above the speed sensor but was still able to do it. With the speed sensor out you now have pretty easy access to the first two screws on the shift solenoid, the third one is under the fuse box hardware, but there is enough clearance to get to it without removing anything else. Be sure you have your drip pan in place because things will get messy soon. Remove the three screws holding the shift solenoid in. Once the screws are removed you will most likely need to pry the solenoid loose. I used a the handle of a large socket wrench, placing it between the transmission and the solenoid. Once you break it loose, quite a bit of trans fluid will flow out. You'll have to position the solenoid to remove it but I promise you it'll come out (well for me it did and I have a stock 2000). You will need to make sure you remove the old gasket that went in between the old solenoid and the transmission. This was kind of a pain in the neck. Once you get the old gasket removed...make sure everything is clean of any dirt and old gasket bits. Grab your new solenoid and place the new gasket directly onto the solenoid. Position the solenoid and put it into place. The easiest way to do this is to put the two side screws in place first and tighten them down most of the way, then put the middle screw in place and get it threaded. The solenoid doesn't exactly sit level, it sort of tilts slightly towards the back. After you tighten up the bolts, reverse the order of removal.
I didn't have to do anything special after putting it back together besides adding about a quart of ATF +4 into the transmission. I kept my foot on the brake and shifted through the gears slowly a couple of times then went for a drive. It shift nice and smooth right away.
I do suggest you keep an eye on the solenoid and the transmission fluid levels. Supposedly the solenoids have a tendency to leak.
I will most likely edit this a little later to make it more accurate. Hopefully this helps others.
Also, if anyone wants to know exactly what my car was doing, basically the car would go into limp mode after driving it around long enough for everything to get hot. While the engine and trans were cold everything worked fine and it shifted fine. After it heated up though, if I was travelling anything faster than 30 mph the car would shift into neutral, than into second gear. Shifting into park, neutral, reverse and drive AFTER it went into limp mode was smooth. Removing the battery cable and resetting the computer allowed me to drive the car until everything got hot again. If I reset the codes using a code reader while everything was hot, it had difficulties shifting right away.