The VSS sensor is a contact sensor. There's a gear on the VSS sensor that meshes with the worm gear.
The OSS sensor is a NON-contact sensor. There's a toothed ring gear pressed onto the tail shaft (like the ABS sensor).
You should be able to remove the VSS sensor and SEE the worm gear down inside the hole. If no worm gear, then there's nothing to turn the VSS sensor. No turning VSS, no speed signal.
I may be in left field here but I don't get the impression that you fully appreciate how ALL of the pieces fit together. Nor do I think the request for additional information have been forth coming. Silversmith82 asked a valid question about the worm gear to which you said no. The later you state a "gray plastic" part was transferred.
This almost sounds like an unfamiliarity with what a worm gear looks like and how it works.
Us out here in Internet land don't know anything more about YOUR car than what is in this thread. We are trying to help resolve your problem but the answers just generate more questions. All replies short with no detail.
Again going out on a limb here. IMO something has been over looked. In an effort to resolve the issue several different options have been "tried" but not all of the pieces have been brought together at the same time. Now so many things have been tried, only confusion remains.
If this were my car, I would go back an re-check all of the work down to the small detail. Ensure that the wiring is sound and the correct parts have been used for which sensor is chosen. Then I would test the individual parts to be sure they are working as intended.
I'm going to drop off this thread now since it appears that I'm no longer helping. Good luck.
Hey guys Ik it’s been a while since this had been active but I have a 1999 gt with a 2003 gt motor my current trans is toast and I found a 4r70w out of a 98 that I could throw in. After reading this form I’ve been extremely discouraged but I wanted to see if anyone knew what I’d need for this swap.