On my 88 300TE 147,000Km, everytime I shift gear say P->R or P->D, or R->D, D->R there is a jolt when the transmission engages

I have changed the Flex discs, transmission oil and differential oil about 7000km ago but nothing has really changed.

I've also tried adjusting the the vacuum modulator about 1.5 turns. The shifting shock during driving has softened but still have jolt when changing gears while parking (R->D, D->R).

Any thoughts on what's wrong? Any remedy to this problem? Perhaps I need to adjust the modulator more?

Thanks in Advance.