2002 model giving transmission problem at D3 D4 gears doesn't engage for a few secs when the vehicle is on load ie starting on incline. 1 2 gears are fine what could be problem is there risk of lockup?

You better get this vehicle to a transmission professional immediately, before serious damage is done. It may be as simple as a transmission fluid change or more severe. BTW, if you have changed the transmission fluid and did not install Honda ATF Z-1 fluid, drain and refill with the proper fluid. Any other fluid will cause shift problems. Don't let anyone tell you different.