Cant leave 1st gear?

Hi all,

So i have this annoying problem...

When at full-throttle accelerating in 1st gear, at red line when i go to change into 2nd gear, the shifter remains stuck in 1st gear for a little while (a second or so).
Once it does eventually pull out of 1st gear it goes into 2nd gear fine. So its just pulling it out of 1st thats the problem.
When not accelerating hard, or not reving as far, it shifts just fine.

Has anyone else come across this?

Oh, BTW its a ST205 gearbox.

Thanks

Ive noticed it in my st205 swap too. Then when it finally pulls out (Feels like forever) it doesn't go immediately into 2nd. Very annoying

What oil you using?

Im using Redline 75w90ns which as far as i can tell is the perfect oil for it.

Some people on Facebook suggested it may be the clutch not disengaging fully.
So ill look into that soon.

funny how i had the same problem with my st205 tranny with my st185! i even had the brass bushings and a new clutch and flywheel. i was also using 75w90