Won't upshift under heavy throttle
 

I've got a 99 camry V6. I've never had any problems with the car until recently. When trying to pass people on the highway under heavy throttle, the car will kick down to a lower gear with no problems. However, if the revs reach anywhere above 4k, the car will kind of "buck" at one RPM when it tries to shift back up to fourth. It's only when i let my foot off the gas that the car will shift back to normal crusing RPM. This has started happening without any warning. The car works perfectly, runs well, and there is no loss in power when driving normally. Any ideas what this could be?

Thanks.

Might check the kick down cable adjustment. The cable connects the throttle pulley to the trans.

With the gas pedal fully depressed there should be 0.04 inch or less end play in this cable.