i have an 89 rs 5.0tbi. last year i had the transmission rebuilt and have had no problems with it. about 2 months ago, my car violently shuddered as i was going down the highway, like i bounced off the governor. i dropped it into third, and it stuttered, but smoothed out. now, it is doing it on a regular basis. i was thinking it was a fuel pump going bad, so i replaced the pump and filter last month. still does it. now my car is throwing a code 24. so i called about a new vss from my tranny shop, and they said it bolts into my speedo gear location? i have a cable driven speedo. i've replaced the computer thinking this was an issue, to no avail. wats going on? i still have the yellow/purple wires leading down to the tranny, but no idea if they still need to be plugged somewhere. its the stock tranny from the car. am i totally retarded here or is there something i'm missing? i'm not wire-savvy or electronically smart so if i cant figure this out i'm converting this car to a carb. so any help would be greatly appreciated

 

also i forgot to mention my car will not lock up in third or fourth.