Hey All, I replaced a SP-300 in my 66 Lark with another SP-300 and now it will not shift into second by itself? It works fine if I manually shift it? Any input? Fluid level is correct, the new trans seems to shift/work well besides for this? Input appreciated before I dive into replacing items one by one! Thanks, Tom
Vacuum modulator plumbed properly? If there's no vac at the modulator it'll think you're at full throttle all the time. Another possibility is that you have a problem with electrical, i.e. detent is seeing +12V all the time. Devon
Devon, Thanks, that will be my first place to look when I get home tonight (It got a little late last night to start diving into everything). So if the vacuum is ok (I just may pick up a new modulator on the way home to play it safe) where would I check the voltage part of it that you described?... Thanks Again, Tom
Hi Tom, if your ST300 is a '66, you'll see a two-pronged electrical connection on the left side of the case above the oil pan (see http://buickperformance.com/switchpitch.htm). I think you'll find the white wire is downshift (detent) and the black is for the variable pitch torque converter. A quick way to see if the detent is the culprit would simply be to unplug the connector from the trans. I suppose even if the detent solenoid isn't energized, it could actually be stuck in position causing the same problem, but I've never seen this happen. Devon
