Manual Transmission - Expert Tranny advice needed please

Well, my fears were confirmed yesterday when I removed the tranny and clutch and found no "visible" signs of a clutch failure. The clutch disk seemed ok and wasn't worn down to the rivets like i thought. The pressure plate didn't show any signs of failure either. While I'm no expert, I must point my finger at the tranny right?
Ok, here's what happened: On a WOT shift to 3rd, it sounded like I missed a gear but felt like I broke the tranny. I went to 4th and everything seemed ok I just cruised in 4th until I got close to home. Then come to find out I still had 3rd, and the clutch engagement felt normal. I had all my gears and everything was normal UNTIL I gave it more gas than say 1/4 throttle. Then it would make a slipping grinding sound and act asif it was in neutral. With normal nursing the car driving it makes no noises and appears fine.
I drained the fluid in the tranny and found no metal. Is there any way I can test the tranny out of the car? Thanks in advance for any advice!
Btw, it was an origional stock clutch that was starting to slip alittle on lauches before the catastrophe. :eyes: 30k miles

Well been there done that, it is doing this in 3rd right?
Sounds like you bent the 3/4 shift fork. It will give you 3rd but not enough to stay in under high power.Also sounds like your stock clutch is also showing it's weaknesses.
It sucks but it's not gonna be cheap, your gonna need to upgrade/or rebuild your T-56 with a steel shift fork. Then a good clutch set & recommend an adjustable master & an updated slave. Do the "drill mod" to your hydraulic line as well.
It wont even feel like the same car by the time your done.

Actually, it did it in all gears. It didn't seem to jump out of gear either. (just slip and grind noise) That's why I just assumed it was the clutch at first. I never checked 6th but it had the same problem 1st thru 5th. Thanks.

Found the problem! I'm very relieved, it was the disk. The weird thing is it looked fine but the internal part of the disk that rides on the tranny shaft was sheared off all the way around and the noise I heard was it breaking loose and spinning against the clutch springs on harder acceleration.
Whew! :)