boy am i an idiot.
haasman steered me in the right direction. i wasn't paying attention to the tach. 60-65mph in 2nd is 6 grand.
somehow my upshift points had been altered - i like them to shift at 5800-5900 - so in kick-down 2nd gear the tranny was letting me run to the redline. and then the rev limiter would engage. had never experienced the rev limiter functioning before.
glad it did, otherwise i would probably have scattered lots of expensive engine parts along the highway.
so, readjusted the tranny. now it shifts just where i think it should, almost at the redline, but not beyond the redline.
thnx for all your suggestions.