[RH77]

Just through observation and the shop manual, I've noted the following in the Integra:

-TC happens at 35 mph or higher (at full operating temp)
-There are 3 levels of TC lockup: partial, half, and full
-Gears 2-4 are effected
-Hill logic control is independent of lockup

The last point helps me know about lockup behavior. Climbing a hill or on-ramp, the TCU will hold the 3rd gear, for example (unless the throttle is lifted). The the unit will then determine that a constant RPM allows some degree of lockup.

The telltale is the shift to 4th. In most vehicles, shifting gears in lockup is jolting -- the full force of the engine output is placed on that gear change (no cushion from the converter). Some cars perform a brief unlock, shift, re-lock -- which is still noticeable and often a hard shift.

Another "seat of the pants" way to tell if you're in lock is to give the vehicle a little throttle pressure and back off. If the tach gently moves 100-200 RPM or more, it's generally not locked (if not, then it shifted out). If I EOC, the TCU gets rather confused and denies lockup until such distance that the Math checks out for the hill-logic control. During full warmup and no EOC, TC lock is deliberate and noticeable right at 35.

I tend to get up to TC lock (35 mph) briskly -- since the ECU retards the timing on every upshift for a "smoother" engagement, FE drops at each shift. It's built-in and I can't do anything about it -- it's probably not a lot.

Some cars react differently, but I've tightened the throttle linkage to the max extent. This creates more fluid pressure for tighter shifts, earlier (and more noticeable). Some will argue that it causes earlier kickdown. It all depends if the vehicle has an aggressive Transmission Control Unit -- in my case it doesn't. I'm also told that harder shifts are better than slipping ones for longevity.

BTW, what kind of car? GM generally has a smooth, sliding action to their TCs and unlock with the slightest lift...

RH77