Hi, the car have been out of commission for a while because it won't go forward in Drive, trans in question is a 6hp26 it will go into reverse well enough, but if i shift it into drive, the car jumps backwards like it's trying to get into reverse and can't go forward or backwards, drive wheels locked up, below i attach a short video of the symptom,

If anyone has had experience with this, or got any suggestions on what to check it would be really helpful. Thanks

 

Check the 2 (8mm hex?) bolts (under car) holding the shift cable to the trans are present and snugged up.

May need to check trans fluid level.

If all OK, may need trans diagnosis...