Trouble getting into drive and reverse

[jusroln]

95 GSX AT with shift kit, high stall TC, upgraded clutches..... When I try to engage reverse or drive I must rev the engine up and down to about 3000 rpms for a few minutes before I can get it to engage. When it does there is a loud clank and jerk (as expected at 3000RPMs). When warm or recently driven it will engage right away but not if it sits for any period of time. I've been trying to diagnose this for years while I have been rebuilding the car. Would be nice to finally get this fixed. Seems to drive ok when rolling. Fluid level is good and fluid is fresh/ filter clean.