07 Yaris Sedan Manual Tranny Problems

[QR25DE_SpecV]

You're experiencing what is called transmission lockout. This is because the synchronizers in the Yaris transmission are small, and weak as hell. There are a few things you can do to combat this though.

First gear lockout is actually very common in manual transmissions, and you'll find very few transmissions that allow you to shift to first gear at speed. This is by design, to reduce the likelihood of you screwing up and valve floating your engine to death. One car I've driven that allows you to shift to first while at any speed is the Lotus Elise/Exige, for obvious purposes.

1) Better fluid. AMSOil is pretty awesome stuff, as already stated in the thread. I'd personally recommend that.

2) Double clutching. This may sound silly, but I promise you it works. In my SpecV you can't put the car in first unless you're damn near stopped. If I double clutch, I can get it in doing 20.

3) Try rev matching in conjunction with double clutching. Both of these will eliminate the need for the syncro entirely, and the gear should slide in.

If you're unfamiliar with double clutching, it's pretty simple. Stab the clutch while taking the car out of what ever gear you're in, release the clutch, then depress the clutch again, and at the same time rev match and slide the gear in.

Works every time with me.

EDIT: I've only experienced transmission lockout on a few other cars, all of which were 'cheap' in nature. The Hyundai Genesis Coupe 2.0T had horrible second gear lockout, even when rev matching. This is either due to cheap design, inadequate syncros, or poor fluid. Probably more than one, if not all of these are the reason why you're having that experience.

EDIT #2: I was thinking maybe it's a linkage issue, but that would also impact 4th gear, which you make no mention of. So I'd say this isn't a linkage issue either.