The cause was that the 4 bushings in my shifter u-joint were entirely worn out - totally gone. Also, the spring that centers the shifter was a little stretched out so I replaced it too. Through much trial and error, I found that it's much easier and equally cost-effective to simply replace the complete u-joint (which comes with bushings). The bushings are about $10ea x 4, and the u-joint complete is about $44 (all at 1stsubaruparts). Additionally, if you replace the u-joint complete, you don't have to worry about grinding off the press-fit pin that holds one side together, replacing those bushings, and replacing that with a bolt. The new u-joint comes fully assembled with the press-fit pin and bushings.
Keywords for search: shifter, rattle, rattling, loose, sloppy.
Did extensive searching here and on other boards but I didn't find anything that quite addressed my exact situation. There were similar howtos for slightly different models but they were incomplete, missing pictures, etc. Hopefully this will help out some people with this overall pretty straightforward fix. Bonus is that I LOVE how my new shifter feels. It's a real improvement and makes the car feel newer and snappier.
Onto the Howto:
Tools you'll need:
-Ramps or really high jackstands (my jackstands weren't quite enough to be comfortable)
-Set of 12mm box wrench/speed wrench, maybe a socket for good measure
-Set of punches/drifts
-Phillips head screwdriver
-U-joint assembly complete: 35047AC030 - $44
-Spring: 33022GA081 - $0.90
-Bolt: 35045FC000 - $1.28 (This is recommended to be replaced in a tech bulletin about rattling. I think my old bolt was fine but I went ahead and replaced it with this one anyway. They appear to be slightly different).
-Spring pin: 633046020 - $1.87 (OPTIONAL - See below)
EDIT: samneric pointed out that I initially put the wrong p/n down for the bolt I used, good eye. I've now corrected it and included a link to the endwrench article. His post has the p/n as 35052AA031, which I think is the p/n for the original bolt. Because I saw the endwrench article I went ahead and used the "updated" one, but I doubt it was the cause of my problem.
Put the car on ramps, set e-brake and chock rear wheels. Wait for exhaust and transmission to cool if you've been driving it. Others have recommended removing the heat shield, even dropping parts of the sub frame to make this easier. You can do this if you want to, but I was able to do everything without removing any of this. The first thing you'll want to do is unhook the spring that centers the shifter - needlenose pliers. Then remove the round plate with the ear on it that the spring was hooked to, keeping track of how it's oriented - it is indexed but at least on my car there was a lot of play in it so I wanted to keep it the same. This is just a 12mm nut on a fixed stud. There's a large black rubber bushing under the plate, I did not need to pull this off the stud in the end but it's easy to do if you need to. You'll want to take a look at this bushing - I've read that if it has deteriorated you'll get front-back play, which I didn't have. My bushing was fine so I left it alone.
The next step is probably the hardest part overall. You need to remove the spring pin from where the u-joint joins the shaft that goes into the transmission (towards front of the car). It is a 2-part spring pin, with an inner and outer. Look very closely and you'll see the inner pin, which has to be removed first. A good set of punches helps here, I got it with trial and error. Be careful not to use too small a punch and actually go into the inner pin. The punch will be very, very hard to get back out. Ask me how I know....
This part is tricky because you can't get a totally straight shot at the pins without removing part of the sub-frame. I was able to get it with the help of a shadetree mech friend, a rubber mallet, and some socket extensions. Patience pays off here. It helps to have one person hold the socket extension/punch assembly and keep it centered while the other person hammers on it.
Once you have the inner pin out, the outer one is next. Unfortunately it's not much easier than the inner one. But they do come out. Once both pins are out, put two hands on the u-joint and slide it backwards off the shaft. It should pop right off. Mine still had a bunch of grease on it from the factory.
Now get your two 12mm wrenches and a phillips head screwdriver and get in the passengers seat. Open the armrest storage box and remove the two black screws. Pull up the plastic piece around the e-brake. Then pull up the plastic piece around the shifter, it just snaps in. It will not come entirely off as it is attached to the shifter boot, that's fine, just pull it all the way up over the shifter and let it hang to the side.
I think you might have to cut a little bit of the rubber in front of the shifter in order to access the following screws. I just sliced it in half and never looked back. Maybe someone else can figure out a better way. But you have to remove the 6 gold colored screws that hold the metal frame over the lower rubber boot. Mine were rusty but came out pretty easily. Then you can pull the metal frame up and over and let it sit off to the side (note that the screw holes are offset, it only goes on one way).
Now you can loosen the bolt that goes through the base of the shifter. This is the other end of the u-joint assembly. Remove the bolt entirely and inspect that bushing as well (it is a combo metal and plastic bushing). Mine was fine but others have replaced theirs. Now the u-joint assembly should be totally loose. You can pull it off the shifter handle and maneuver it up and into the car. No need to pull the rubber off.
Now you can use your 12mm wrenches to remove the bolt on one side of the u-joint and replace the u-joint and the bolt you removed with the new parts (mind the orientation of the ear on the u-joint for the spring. Tighten it down so that the play in the bolt side of the u-joint about matches the play in the press pin side. I have no idea if there's a torque spec on this or not, I just did what felt right.
Drop the new u-joint back down under the car and loosely reassemble everything in the car, but don't reattach the rod to the base of the shifter yet. First you need to go back under the car and align the u-joint and slide it back onto the transmission shaft. Drop a screwdriver or small bolt in there just to keep it in place while you go back up and put the bolt in to attach to the shifter lever. Just put the nut on loosely.
Now you need to finish attaching the u-joint to the transmission shaft. You have two options - spring pin or bolt. The spring pin is the "right" way to do it, and will result in the tightest possible fit with no slop. But it was a significant pain to get the spring pin back in there. I ended up reusing the old outer spring pin and inserting the new inner one in it. I simply could not get the new outer pin to go in there. I'm sure you could do it on a bench or maybe if you dropped the frame but that's up to you. By the way, a handy trick is to find something of about the same diameter (bolt or something) and put it in the top. This will help keep the u-joint from spinning relative to the transmission shaft while you're pounding on it). It feels solid to me but if the spring pin falls out I'll update this thread..
The other option is to find a bolt of the right length and size to fit in there. It need to be as close to the exact diameter of the hole as possible - any slop here will translate noticeably to the shifter and depending on how bad it is can make it nearly impossible to get into 5th/reverse. Again, ask me how I know. It might even be worth gauging the old pin when you get it out and getting an exact size bolt with the right size shoulder etc from mcmaster or the hardware store. Of course you'll want a jam or locknut, or locktite. I used a 5/16" bolt and it was pretty close but not exact, it also wasn't the right length so I had to stack lots of washers on it. It worked for a week while I waited for parts but it wasn't a long term solution.
Once you've got either a bolt or the pins back in there, you're home free. Go back up and tighten everything down (esp the bolt through the base of the shifter knob, this can work itself loose in a short period of time - AMHIK...) and put all the plastic back in place. Move all the tools from under your car, take it off the ramps and for a test drive. Enjoy your new shifter. It really feels like a brand new car.
-In my searching I found a few threads, here or on other forums (but linked from posts on this forum) with people talking about finding better bushings on mcmaster or other places. If these wear out in the next 50k I'll consider that, but the rattling didn't start until 135k at the earliest so I have high hopes for these. Plus, much less hassle than grinding off that pin and replacing it with a bolt (on the u-joint assy itself).
-I've also seen people talk about putting a short shift kit on while you do this. I guess you could, but with the new bushings the shift feels shorter and tighter than any other manual I've driving, including my 944. So, do it if you want to, but I think most people will be very pleased with simply bringing the shifter back to spec.
I have a few pictures of this, but I'm not sure how best to host them - I don't have any hosting space of my own and it looks like you can't actually upload images, just link to them - let me know if I'm wrong or you want to host them. I'd put them on imgur or something but then they'd just disappear after a few weeks/months.
Questions? Comments? Let me know. Hope this is helpful to medium mileagers who might have the same problem.
Edited by ernestedward, 11 October 2010 - 01:49 PM.