Shifter locked-up (6 spd)

[driveslikejehu]

First time really driving the car was this track day. The only significant problem to arise was the shifter becoming stiffer and then locking in third gear.
It's a 2006 STi 6-speed btw
At the end of both sessions, I could feel it sort of tighten up- become more difficult to shift. Then after 2nd session and sitting for a few minutes it was locked into 3rd gear. The shift rod really seemed stuck, not like internal broken gear interference or something. Later inspection showed what might be new wear marks on the shift shaft.
shift shaft 1.jpg

Decided to have lunch, give up for the day and flog the Cayman for one session. After a couple of hours, I could shift normally enough to load it on the trailer. Next day seems normal. This all really makes it seem heat related.
Given that aluminum has twice the thermal expansion rate of steel, it’s kinda hard to see how the shaft could expand enough to seize up. But that’s what it looked like. Is it something deeper inside?

I loved to hear thoughts on this. I haven’t yet searched thru the forum for similar experiences.

Though it may not be relevant, my ZDB set-up never has felt great. Though it seems properly adjusted, it has always feels a bit “crunchy;” doesn’t smoothly go into gears. Maybe just worn synchros, but never sure if I have the cable/shift rod linkages adjusted properly. Might just be the 107,000 miles trans needing to be rebuilt.

[Hobby Racer]

... Might just be the 107,000 miles trans needing to be rebuilt.

I'm assuming you have never had it apart except for the 2WD conversion, correct? Have you changed the fluid since you got the trans? If so, what did you use?

[driveslikejehu]

I flushed clean oil thru it when I did the 2WD conversion. After it was a little warm from go cart drives, I drained and filled with fresh. I used the spec in the manual; 80-90 GL-5.
Would affect are you suggesting? I know you have a lot of experience with these things...

[Hobby Racer]

That oil is fine. It's important to use a GL5 grade. I'm wondering about your 2WD conversion. Did you use the FFR 6 spd conversion kit or did you roll your own?

Do you have any pics from when you did the conversion?

[driveslikejehu]

Yes, I did it with the FFR kit.
I don't have pics... It was like the first thing I did, and before I started documenting the work
I remember it being pretty much "by the book" with the 6-spd supplement.

[Hobby Racer]

Unfortunately it sounds like a tear down and careful inspection is going to be needed.

[idf]

How does it feel when you disconnect the cables and shift it manually from the back? Can you get all the gears?

[driveslikejehu]

When it was hot, I disconnected the cables and couldn't move the shift rod. After a couple hours of cool down I gently pried it out of 3rd (inward position). A few minutes later I could move to all gears by hand. Reconnected all; by end of day, drove it thru the pits and onto and off the trailer.
Unfortunately, I agree that pulling at least that rear housing is needed to see what's what. I'm hoping a full trans rebuild can wait till the winter.

[driveslikejehu]

Fortunately, its pretty easy to get to the rear transmission housing...
I drained the oil and pulled to pan; no debris, just usual transmission sludge.
I expected to find just a plain bearing for the shift shaft, but it has a gaged ball bearing. Makes sense, to allow for radial and axial shaft movement.
The bearing looked ok, wasn't dry, though I don't really see how oil gets to it
shift rod bearing.jpg
The shaft looked a little burnished where it rides the balls. The groove looks typical for a shaft seal.
shift rod 2.jpg

One thing that caught my attention is the oil guide not being installed. I didn't remember this from the instructions. I see now that it must shoot oil into that passage that was blocked off when the tail is removed. So that's why I left it out? Should it be in there?
It goes in this hole
oil hole.jpg
Looks like this
oil guide.jpg

So nothing is jumping out as to why the shaft stuck. It really seems like heat as it was normal when it cooled down. I didn't have shielding between the trans and exhaust pipe and had an exhaust hanger direct bolted to the rear trans housing.

I plan to replace the shaft bearing and seal, install a heat shield and insulate the bracket bolt locations.
Any other thoughts, ideas?

[Hobby Racer]

That tray catches oil that's slung off the center diff and any oil that pools in the back cover where the output shaft used to be. You should put it back when you reassemble, but I do not believe that is source of your issue.

[Bob_n_Cincy]

On the 5 speed transmission they also use a linear/rotating bearing that is lubed by oil flung off the center diff (that is no longer in our transmissions) I sealed off my housing so no oil makes it into the center diff housing. To lube this bearing I used some red high tack grease.

dhaft bearing.jpg