torque converter question

my truck has a 4l60 with a lockup converter, now when i bought my truck he told me it had a new trans because the other one too a dive cuz they were haulin heavy machinery, i originally thought my trans was shot because it would shift real real late. but now i think its the torque converter. when i just cruise the trans shifts nice and firm. but when i get on the gas it acts like the trans is slipping (it revs real high real quick like its in neutral) but after a couple seconds it shifts firmly so im thinking when they replaced the trans they left the original converter.
what do you guys think?
thanks
stevey

I believe that those symptoms are common for the early 4l60s, theres kits to fix it, like this one

http://cgi.ebay.com/700R4-700-4L60-T...QQcmdZViewItem

others on this board are better on the mixer questions than I, I'm sure they will chime in, good luck.

thanks man

its not the converter like you said the trannys slipping

yeah overdrive and drive went out on me last week