Was driving today on a 55mph 2-lane. Car in front of me was driving along at 45mph. I had my TC locked (manually), and was thinking about how it seemed to 'grunt' or 'vibrate' more at this slower speed (vibrate is not a good term, but I'm at a loss for the right words to use to describe). At 55mph+, everything is always smooth sailing with TC locked.

I noticed that, at this 45-50mph, my rpm is right at about 2200 (assuming my tach is relatively accurate). My TC stall speed is right around 2200-2300 (I'm running the S-10 converter behind my 350). I can tell by watching the tach and accellerating slowly from a stop that ... my car seems to "catch" if you will right about 2300 on my tach, matching what I was told the S-10 converter would stall at behind a 350.

So - my question is ... is the 'not running so great, smooth, whatever you want to call it ... is that because at that lower speed, I'm coming down close to the "stall speed" of my converter?

I mean I know the lockup basically fills the converter full of fluid, so there's no "room" for any speed difference between the tranny side and the motor side. But I was thinking - although it's "full" of fluid (locked), is it still kinda fighting itself to "stall" if you will at these lower rpms?

And I know in a stock 3rd gen, converter 'stall' was way lower, like 1200rpms, and thus there was no issue with the ECM locking even in 3rd at like 35mph, because engine rpms were still higher that TC "stall" speed (in my little theory here). But if I try to lock mine now at such a low rpm, I basically get a kinda 'chugging' feel - because I'm not going fast enough - at higher speeds (ie higher rpms), it's smooth sailing.

I'm just not sure how exactly all this works, intuitively I understand, but in reality not sure I could explain it very well to another (how a TC works that is), and then especially when we start talking about "locking" it. So, if someone could (in layman's terms please), tell me if I'm way out in left field here, or does my question kinda make sense?