and the plot thickens,,, if its a 700r4 then if the torque converter clutch is not being told to engage it will slip on shift or if the tv cable is not adjusted right or broken. the noise would be the big concern. try and get a recording of it.

 

The only way the torque converter itself is going to slip is if it's bad internally. The clutch in the t.c. is what locks it up, only in 4th gear cruising, not during 1-2-3 shifts. If the lockup clutch doesn't work at all, the t.c will just operate like any other conventional t.c.
Weird thing is, he heard the noise in back, but some noises can travel. Yep, a sound recording might help.

 

the trans i have now locks up in third. its a 93 though. i have 5 wire plug with lockup wires for 2nd 3rd and 4th. 4l60/700r4, must be another one of those 93 things.

 

Hmmmmm...has your trans been wired differently from how it came from the factory? The 700R4/4L60 has always been designed to lockup once the car is loafing in 4th. Locking the t.c. clutch in a lower gear can damage the clutch since it isn't designed to take the torque of hard acceleration.

 

wireing is stock tranny and converter is not. supposed to handle 600 hp.

 

If i had a decent camera, I would get a recording. Now it seems the noise has gone but 1st and 2nd gear are slipping so bad that now i'm afraid to drive it up the road because I cant get out of my own way.

 

Pull the trans dipstick and give the fluid a good sniff. Does it smell burnt, and/or look brownish in color?

 

The fluid is still red, It doesn't smell burnt. But when I cut the car off after driving it, I do smell something burning.

 

Is your TV cable connected and adjusted correctly? Craby mentioned that earlier, but you didn't say anything about it.

 

^^^ plus if the cable is good and adjusted right it could be cracked sun gear with the grinding noise you had. dont know if that would effect the line pressure. try looking here. some of them are the same as the 700r4/4l60.
http://www.gmtruckhq.com/?q=node/93
also good info here.
http://www.700r4l60e.com/