Took my car out to Woodward tonight. After a few miles of driving I was coming to a stop and the car started bucking. I knew immediately that the TCC solenoid had given up the ghost. I pulled into a parking lot thinking I could unplug the connector, but that wasn't going to happen until everything cooled down. That plug is in close proximity to the exhaust crossover and the cross engine coolant tube. I was able to limp the car home and got out my Helm manual to see what the replacement procedure is. I went though every page of the automatic transaxle section and did not find anything for the replacement of the TCC solenoid. The only thing I did find is the wiring diagrams (figures 99 and 100) on page 125C-42. From those diagrams it appears that the TCC is wired to the "switch, 3rd clutch pressure".
So I came here to the knowledge source of all things Fiero. I did several searches using different search terms to see if anyone had posted a "how to" thread with pictures. I did not find anything in my search. So I am wondering if anyone is aware of such a post? If there is one, could you please post a link to the topic.
Second question, if I am replacing the TCC, do I have to replace the "switch, 3rd clutch pressure" as well? Is that switch a separate item from the TCC? Based on the wiring diagram I might think that a TCC solenoid would come with that switch as they are wired together.
It's not difficult. The only problem I had was not being able to find a gasket for the cover. I ended up breaking out a roll of gasket material and making my own. The link above is what I used. I only did the solenoid.
People like to recommend replacing the third gear switch, but I only replaced my solenoid. The hardest part is connecting the wires, inside the tranny. Some solenoids have a plug connected. They just plug in. Others come with crimp connectors. Mine came with the plug, IIRC.
As Fiero repairs go, this one isn't too difficult. Here is another good "how to" from Oliver Scholz (fieroluke here on PFF); no pictures, though. If all else fails, you can buy a new side cover gasket from your local GM dealer, since they are common to all the THM125 transmissions.
The job is not difficult. Getting to all the bolts to remove the side cover is. Easiest way is to jack up the rear wheels off of the ground, strip the left wheelhouse of the strut, hub assembly and wheel support bracket. Then you can pop out the wheelhouse liner and access everything from the side. .
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Powerlog manifold, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
I am way behind on reading the forum. Did you get this done yet? If not, I posted a very long message earlier this year. Have a look. I have to go help my nephew move, but I'll be back later tonight.
Assuming this is a V6, it is really easy. You do have to jack up the driver side and remove *everything* under the body. Go get new plastic rivets and repalce them when you put the wheel well and splash guards back in. The really hard part is getting that blasted connector on at the top of the housing. Just that one task took me about 15 minutes before I was sure I had it snapped in place.
I'll check back tonight in case you didn't find my last post.
Didn't get it done yet. Just got the 3rd clutch pressure switch on Friday. I had to got to a couple different places to get it. Now I have all the parts, I just need to do the job.
lateFormula: The link above this post is a good one. I agree that it is a rather easy fix as Fiero work goes. I did not change the third gear switch, but it sounds relatively easy.
I will echo the tips: you will want to clean things up while you have it apart. 1) You really have to take all of the stuff out of the driver side wheel well. It is just held in with those plastic rivet things. I bought a whole bunch for basically nothing at Autozone. Well worth putting it back together with the right "hardware" 2) Once you have jacked up the car and removed the driver rear wheel, all the splash guards and the wheel well itself, you are looking straight at the transmission cover you want to take off. Put a drip pan under where you are working. You will loose about a quart of transmission fluid once you break the seal. You get a lot at first and then it just keeps leaking. 3) You will need to take some of the bolts on the top of the cover out while standing in the trunk. 4) I did not know about releasing the cable from the transmission to the throttle body, but it sounds like a good idea (see other post). Getting the connector off and the new one back on took about 20 minutes and I was never really sure that the lock had snapped into place. 5) Once you have the cover off, you are looking straight at the TCC solenoid. It is at the bottom of the transmission and is held in place by that single Torx. The hard part is getting the connector off at the top left. From the description, removing that cable moves the thing that blocks access to the connector. You need a very thin screwdriver to pop the catch off the connector. I use a small green Xcelite one (primarily an electronics tool company). It is a very thin screwdriver that lets you get under the catch. I didn't really need the mirror, but I am used to doing things by "Braille". Your mileage may vary. 6) Take the plastic protector off the old solenoid wiring and install it on the wiring of the new one. Put the new solenoid in and route the wires back up to the connector. This is the part that I had trouble with. You have to get the connector aimed correctly and then get enough force on it to get it to snap in place. Again, I had stuff in the way that apparently moves when you release the cable and makes the job a lot easier. 7) my cover did not have permatex on it when I removed it so I did not use any to put it back on. You just need to get the bolts snug to keep it from leaking. I agree with putting a couple of bolts through the cover and gasket to hold in place. Then use a 1/4 drive as someone else suggested to tighten the bolts. You DO NOT want to over torque these bolts. I learned the hard way on a Fiat aluminum transmission housing that aluminum is *really* easy to strip.
I sure hope this is a once in a lifetime job, but I will know how if ever a next time. (still drooling over the 88 GT for sale in Kingsland with 46000 miles)
I notice the AC Delco solenoid (#8689901) has extra wire and connectors on the ends, the other solenoids just have short leads and a wire connector on the end (which means you'll be cutting into the original wires and making a connection). Usually I'd not want to do that because it's just another place for a possible failure, however, is it a pain-in-the-ass to route the wires and make the connections if I order and use the AC Delco solenoid when installing the part???
Also, I'm a little confussed about the "3rd gear switch". Is this also refered to as a "pressure switch". I'm having trouble finding that part anywhere (I did find it as a pressure switch at the Fiero Store, but wanted to make sure it was the same thing as the 3rd gear switch...).
OK here are the part numbers I found. All of these are available on RockAuto.com. The 3rd clutch pressure switch was the tough one to locate. I am planning to do this repair this weekend if the temperatures here cool off some, so I cannot verify that the part number for the 3 cltch pressure switch is correct. I went to a local trans shop, and they sent me to a local office for Transtar, which is a nation wide transmission parts supply house. Here's the numbers:
TCC solenoid - AC Delco 8689901 - price at Rock Auto - $27.79 Pressure switch -AC Delco 8643710 - price at Rock Auto - $5.99 Side cover gasket - Fel Pro TOS 18661 - price at Rock Auto - $5.18
Further information - RockAuto shows the part number for the pressure switch as an AC switch. It is entirely possible that this same part number can be used for this application, but the AC Delco catalog lists that part number as "3rd clutch pressure switch". ALSO, the pressure switch uses the same part number as a GM part number. If you wanted to go to a dealership to buy this, that part number would work.
OK here are the part numbers I found. All of these are available on RockAuto.com. The 3rd clutch pressure switch was the tough one to locate. I am planning to do this repair this weekend if the temperatures here cool off some, so I cannot verify that the part number for the 3 cltch pressure switch is correct. I went to a local trans shop, and they sent me to a local office for Transtar, which is a nation wide transmission parts supply house. Here's the numbers:
TCC solenoid - AC Delco 8689901 - price at Rock Auto - $27.79 Pressure switch -AC Delco 8643710 - price at Rock Auto - $5.99 Side cover gasket - Fel Pro TOS 18661 - price at Rock Auto - $5.18
Further information - RockAuto shows the part number for the pressure switch as an AC switch. It is entirely possible that this same part number can be used for this application, but the AC Delco catalog lists that part number as "3rd clutch pressure switch". ALSO, the pressure switch uses the same part number as a GM part number. If you wanted to go to a dealership to buy this, that part number would work.
Even Oliver's page links back to it. 
