I have 85 Camaro 2.8 liter and it has the 700-R4 transmission, and after fixing my previous problem I was test driving it and 3rd and 4th gear just went out. You can manually put it in 1 or 2 and they work but when you shift to 3rd or it automatically shifts to 3rd it is just like hitting neutral. The shift linkage had a bolt missing and the other was loose so I fixed that and checked the fluid but still the same problem. Is it possible that the TV cable has something to do with this? I have never disconnected it or anything but I was crawling all around the engine compartment trying to get the distributor out earlier.

 

Sounds like you need a tranny rebuild. The 3-4 clutches are toast.

 

Same thing happened to my 89 marquis. The grommet for the TV rotted off the throttle body and I burned up 3rd and 4th, just like you said went into 2nd fine but then felt like neutral. If you catch it soon enough you may be alright, but if its already neutral it probably toast. It cost me $1200 to get mine rebuilt. Good luck.

Chris