1982 300D Hard Shifting and Flaring ??

I changed the transmission fluid and the filter 300 miles ago; lately, when I start driving, the car seems to stay in first gear too long and then suddenly jump into second gear; it makes the rear wheels chirp;
it then shifts quickly from third gear to fourth gear.

I am looking at the following:

1x 616 617 Diesel Transmission Vacuum Shift Valve Dashpot Upgrade $10.85
1x Diesel Automatic Transmission Peak Performance Tuning - NEW MANUAL RELEASE

Can you help?

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