When should a 700r4 lock the converter?

[dhumboldt12]

I've got a 91 k1500 with the 700r4. Around 120k, and was wondering at which point should the converter lock when warmed up. Currently it locks in 3rd, and 4th. And also when you give it gas in 3rd, it unlocks, then locks up again when you don't pick up enough speed to shift into 4th. Normal?

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[Rock Hard Concrete]

Under normal driving conditions my 700 will lock the converter in third before it shifts into 4th if it is up to temp. If i shift manually i can lock it up in second. My transmission seems to work just as well as any 4 speed auto should so i think yours is pretty normal.