i have been in a 2004 when this has happened, so i've seen it first hand. in my case we were going up a steep incline in first gear at slow speed and all of a sudden it popped out of first gear. Car was completly in gear and was fully warm. some drivers will blame themselves and second guess that perhaps they didn't fully shift into gear but trust me this is a real problem if it happens to you and you are in the middle of a left turn in front of oncoming traffice. BE CAREFUL

 

Mine pops out when I'm just about to get the car going ... i.e. when I'm half way through the clutch

 

Mine (MY04) has done it to me twice, and both times I think the cause was I didn't put it into gear far enough. Oddly enough, I replaced the shift knob with a very heavy unit (dumb logic, but it should be harder to pop out right?) and it hasn't done it since.

 

That scared me today! Luckily it always pops out at neighborhood lights. Sat at a light, went to neutral let off the clutch, pushed the brake, pushed the clutch in switched to first I am paranoid so I put it in first and was like hmm, put it back to neutral with the clutch still pushed in, and put it back into first a second time. When the light turned green it wouldn't go into first gear. Let off the gas, clutched it, pushed it, it grinded, another second, pushed it back into first, and got the hell out of there as quick as possible not to piss off the people behind me (luckily the light didn't turn red for like 5 seconds after I went).

 

Didnt finish reading the posts, but i got first hand experience with a Synchro going out.

My Celica, 5th gear starting popping out, first rarely, then more often, then i had to put a finger to keep it in, then, Pop, GRIND, CLUNK, Redlined.

Exact same characteristics your describing. Sometimes went in perfect, sometimes had to "pop" it in.

Get it rebuilt or inspected before you go on any lengthy trips. When mine went i was 900 miles from home and 1000 miles from my destination.

Good Luck.

 

This is exactly what was happening to me '04MY. Half way through the clutch it would just pop out of 1st. Only happened a handfull of times though and I never thought much of it. Wish I could help but I never did get it looked at.

 

My tsx used to do the same thing and each time it was because i was sloppy on the shifting and didn't put the lever all the way into gear. A heavier shift knob logically makes sense.

 

I have an idea to try next time I feel it happening (I can tell it is not clicking/sticking into first gear and get paranoid). Hand Brake up, clutch in, 1500 rpm and stick it from neutral into first.
Simply when it is stopped at a light and I am going from neutral its not locking in. I never have a problem like this when I am slowing down at a stop sign and push it into first while moving. Sorry for my ignorance, but it might be the flywheel? or something because you can kind of feel like something is very lightly blocking it when the s2k is above 1k rpms, clutch depressed and pushing it into first. Whenever it pops out of first gear I can tell it does not feel like anything is "blocking" it while pushing it into first or keeping it in place.
It popped out of gear today when I was at the front of a turn signal line >.<. I might test how it feels to rev it up to 1,500 while it is stopped in the parking lot tomorrow morning and pushing it into first.
It is a horrible error and I wish I had a warranty on the car brand new to fix because this is obviously not a new problem that the old owner didn't have. It is happening about once a day now. I never have a problem when the car is coming from a fresh start and is idling at like 1500 rpm or whatever while warming up.

 

Read my reply man.

It doesnt matter what RPM your at when putting into gear, entire purpose of a clutch is to seperate your Engines crankshaft from the tranny.

 

It can't hurt to try haha. Its a weird problem and I as a student I am all about trial and error . Plus that was your Celica.
Maybe the reason it works when slowing down is because of the wheels are still spinning though.
May also try holding it in when engaging if I feel that happening and see if it will make the grinding or go into the gear. Because when it pops out, you push in the clutch, and the rpms are still a little above 1,000 it grinds if you push first gear forward and have to wait for it go back to idle 800 rpm.