Originally Posted by Lthompson
HOw come when my modulator valve comes unhooked,,, it seems to make my stall work,,, but with it hooked up,, i never can seem to get it to stall any,, it has a little bit,,, but its a B&M holeshot 3000,,,( i think, i cant remember what i put in it) it never seems to stall even when i mash the throttle hard.... Ive got a decent amount of low end torque anyway and it dont hook up either,, but its never seems to accually rev to 3000 and then engage,, but it will if the vacuum is off of it,, but only in 2nd and 3rd gear,, Motor is a 383, AFR heads,, 10.1 compression, demon 750, Comp XEHR 288 i think,, edelbrock rpm intake. anyway,,,, just wonderin,, thanks
I am not a trans expert, only a user. I leave the trans business to the specialists. (actually I clutch-powershift a 5 speed stick)
First, I am not entirely sure what a modulator has to do with stall speed. I thought nothing, based on my automatic years with TH350/400s. I thought the modulator controls the partial throttle shifts by over-riding the governor.
Second, by your description it seems that you might misunderstand what "stall" is.
"Stall", if we can use that term (?), is the actual rpm at which the converter slip is reduced to about 5%. Below this rpm the converter might be slipping a greater percentage, often quite a bit. A higher torque engine will make a specific torque converter "stall" higher. It doesn't just let the engine spin up and then engage, it is a gradual process based on power input and resistence to movement.
By holding your foot down on the brake solidly, and mashing the gas instantly, you will see the rpm increase to a "flash" point, then recede maybe 2-300 rpm. This is the "flash" stall and the "actual" stall rpms.
When the trans output shaft is spinning, and the vehicle moving, the converter will still slip and jump rpm a little. As the transmission output shaft rpm increases the engine flash is reduced significantly until almost none can be induced when popping the throttle, hence a passing-gear kickdown is needed.
Never rule out the possibility of a bad or incorrect converter.
Anybody else help us here?????