Huntervf
Bored now
Since I thought my trans was toast and then found it was just a c clip, the least I could do was share the procedure with the rest of the community! I do have this submitted at SHOtimes.com, but since they have over 200 submissions pending I'm thinking we won't see it anytime soon, so here's the complete how-to (with pics) on this relatively simple procedure 
If you've lost just 4th gear but the trans still works reasonably well in the other three, you may have simply broken a c-clip on the 4th gear servo. The good news is that a replacement clip for about a buck is all you need for parts. The bad news (and it's not even that bad) is that it can be a little difficult to replace with the trans in the car. Now that I've done it, I could make the repair in less than an hour, possibly quicker if I had a nice set of ratchet wrenches.
Before I get into the procedure, I want to point out that I did have some slippage in overdrive just prior to this happening, and once I lost 4th the computer did set a code (638 I believe, 4th gear failure) and I had slightly erratic shifting in the other 3 gears. Given those symptoms I was convinced something major had happened internal, but they all appear to be related to just that c-clip breaking. Perhaps the computer remaps the trans operation in the event of O/D failure, I don't know. But I do know I'm very glad I checked for the broken C-clip, and with it replaced the trans is shifting a-ok through ALL gears once again.
Now, on to the procedure:
This is the servo shaft and cover; it's little more than a metal shaft with a big spring over the whole thing, a small spring held by the infamous c-clip, and a flat piston that rests in the servo cover.
This is where you'll find the servo. Sorry for the blurry pic; it's hard to get good shot in the fender. The camera is sitting where the driver wheel would normally be, looking towards the passenger side. You'll notice the tie rod in the right side of the pic; it's quite crowded in ther with limited space, hence the ratchet wrenches or a 1/4 drive socket wrench. This pic shows the cover and servo already removed; simply remove the driver wheel to gain access. The cover is right on the trans and faces directly towards the firewall and steering rack. In fact, there's barely enough room between the trans and the steering rack to get the servo out. The cover is held in by three 8mm bolts; I used a 1/4 inch socket wrench for the bottom two and a standard 8mm wrench for the top buggar (too tight to get the socket in there, and I didn't feel like going out to get a ratchet wrench set.)
Once the bolts are out, you'll likely have to either gently pry the seam of the cover with a flat head screwdriver or twist back and forth with your hand. It is spring loaded, so once it comes loose it'll pop right out. The cover will hit the steering rack; I found it easier to remove the cover from the servo first, then remove the servo assembly.
Again, sorry for the blurry pic... guess my camera sucks! This is the complete servo assembly, the cover is on the right, with the shaft, piston and smaller spring in the middle. The large spring on the left goes over the whole shaft and just rests against the servo cover.
The culprit itself. There are actually two of these thumbnail-sized clips holding the small spring in place on the shaft, one in back:
and one in front:
I found the front clip to be broken on my 93 ATX, so as soon as I had the cover off I saw the smaller black spring loose on the shaft. After I removed the servo I found the broken clip laying in the trans. When installing the new clip, make sure the you have the small shield on the black spring facing AWAY from the piston, as pictured above.
Now, the hardest part of the job for me was reinserting the servo into the trans. I found it easier to have the whole thing assembled (servo shaft into the cover) for installation. Spread a little bit of Vaseline around the edge of the servo cover to help it all slide back into place. Make sure the pointed end of the servo shaft is inserted into the slot in the trans... I had to go by feel since it was impossible for me to see but you'll easily know when it's properly slotted in. When you're confident the shaft is in the right spot, push the assembly back onto the trans. You'll need some arm strength, because not only does the cover make a tight seal against the trans, but you'll have that big honking spring pushing back as well. Here's where the vaseline will help, as you'll be able to slide the cover on far enough to get your 8mm bolts started. I personally didn't push the cover all the way on, I got my bolts started and then torqued them down in sequence, giving each one a few turns at a time to ensure the cover was going back on straight. Once they're tight, put the driver wheel back on and go enjoy having a fully functioning transmission again!
If you've lost just 4th gear but the trans still works reasonably well in the other three, you may have simply broken a c-clip on the 4th gear servo. The good news is that a replacement clip for about a buck is all you need for parts. The bad news (and it's not even that bad) is that it can be a little difficult to replace with the trans in the car. Now that I've done it, I could make the repair in less than an hour, possibly quicker if I had a nice set of ratchet wrenches.
Before I get into the procedure, I want to point out that I did have some slippage in overdrive just prior to this happening, and once I lost 4th the computer did set a code (638 I believe, 4th gear failure) and I had slightly erratic shifting in the other 3 gears. Given those symptoms I was convinced something major had happened internal, but they all appear to be related to just that c-clip breaking. Perhaps the computer remaps the trans operation in the event of O/D failure, I don't know. But I do know I'm very glad I checked for the broken C-clip, and with it replaced the trans is shifting a-ok through ALL gears once again.
Now, on to the procedure:
This is the servo shaft and cover; it's little more than a metal shaft with a big spring over the whole thing, a small spring held by the infamous c-clip, and a flat piston that rests in the servo cover.
This is where you'll find the servo. Sorry for the blurry pic; it's hard to get good shot in the fender. The camera is sitting where the driver wheel would normally be, looking towards the passenger side. You'll notice the tie rod in the right side of the pic; it's quite crowded in ther with limited space, hence the ratchet wrenches or a 1/4 drive socket wrench. This pic shows the cover and servo already removed; simply remove the driver wheel to gain access. The cover is right on the trans and faces directly towards the firewall and steering rack. In fact, there's barely enough room between the trans and the steering rack to get the servo out. The cover is held in by three 8mm bolts; I used a 1/4 inch socket wrench for the bottom two and a standard 8mm wrench for the top buggar (too tight to get the socket in there, and I didn't feel like going out to get a ratchet wrench set.)
Once the bolts are out, you'll likely have to either gently pry the seam of the cover with a flat head screwdriver or twist back and forth with your hand. It is spring loaded, so once it comes loose it'll pop right out. The cover will hit the steering rack; I found it easier to remove the cover from the servo first, then remove the servo assembly.
Again, sorry for the blurry pic... guess my camera sucks! This is the complete servo assembly, the cover is on the right, with the shaft, piston and smaller spring in the middle. The large spring on the left goes over the whole shaft and just rests against the servo cover.
The culprit itself. There are actually two of these thumbnail-sized clips holding the small spring in place on the shaft, one in back:
and one in front:
I found the front clip to be broken on my 93 ATX, so as soon as I had the cover off I saw the smaller black spring loose on the shaft. After I removed the servo I found the broken clip laying in the trans. When installing the new clip, make sure the you have the small shield on the black spring facing AWAY from the piston, as pictured above.
Now, the hardest part of the job for me was reinserting the servo into the trans. I found it easier to have the whole thing assembled (servo shaft into the cover) for installation. Spread a little bit of Vaseline around the edge of the servo cover to help it all slide back into place. Make sure the pointed end of the servo shaft is inserted into the slot in the trans... I had to go by feel since it was impossible for me to see but you'll easily know when it's properly slotted in. When you're confident the shaft is in the right spot, push the assembly back onto the trans. You'll need some arm strength, because not only does the cover make a tight seal against the trans, but you'll have that big honking spring pushing back as well. Here's where the vaseline will help, as you'll be able to slide the cover on far enough to get your 8mm bolts started. I personally didn't push the cover all the way on, I got my bolts started and then torqued them down in sequence, giving each one a few turns at a time to ensure the cover was going back on straight. Once they're tight, put the driver wheel back on and go enjoy having a fully functioning transmission again!
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