this is not in a buick but is a 2004r. I used to be able to hold first manualy and it wouldnt upshift till i moved the shifter up to second.
now if left in first it will upshift about 5000rpm
when it used to hold up to the 6500 rpm shift point any help would be greatly apreciated
Some things to check:
- leak in the separator plate/VB
- Governor loose/or passages plugged
That said, the 5000 RPM upshift is actually NORMAL behavior for most of the valve bodies!
It sounds like your transmission actually "fixed" itself... It usually takes some sort of shift kit to allow you to hold 1st gear like that...