Long story, if you want to just skip to the 4th paragraph.

So to begin I'll give a little info on the car. Me and my friend found this car on craigslist about a week ago and my friend was in the market to get a new car so we decided to load up his little s-10 and drive 2 hours to check out this camaro.
The camaro is a 1984 Z28 with a 1991 350 Sbc out of a silverado in it. The engine has been bored .40 over and has comp cam in it with ported and polished "double hump" heads. Instead of going with EFI the guy decided to go a different route and put a edelbrock high-rise intake on it with a edelbrock 650 carb on it with a K'n'N low profile air cleaner and headers wrapped in header wrap with a full custom exhaust. Along with this he put different rocker arms and changed the valve covers and basically went through all of the motor to make sure it could handle the power. Checked the push rods, valves,ect. Anything he couldn't do him self he took to a reputable shop in the area. He had over 3500$ worth of receipts and those weren't even all of them.
Now this is where the problem comes in, He is making all this power and he said that he had the transmission looked through and we believed him to a point. It had a slight problem with popping out of 1st on hills but we didn't think much of it at the time. We figured the scyncro is going bad, or maybe the transmission didn't have enough fluid.
We took the car out and put it through some rigorous driving, the same way rowdy teenage boys like ourselves would drive it. And it handled it just fine. No grinds, and it didn't pop out of gear after driving it around on the highway and around the town for about 2 hours. We looked under the car to check for rust and unseen problems, and from what we looked at it was just fine.
For 2600 we thought we were gonna get a steal so he bought it and drove it 2.5 hours home and got 22mpg on the highway all the way home.

Later that night he let his dad drive the car, and to elaborate his dad has no self control in cars. When we went out to take it out for a drive we really beat on it. Like to the point where we were worried about the car, he was in 2nd gear and popped in the clutch and reved it up to around 5000 rpm and dropped the clutch while rolling like 30mph. Then he kept up his assault by accidentally trying to shove it from 2nd at 6500 rpm to 5th, and all it did was grind. Didn't go in and he just kept trying to shove it in. After the drive my friend couldn't put it into 1st and 2nd was going out. The next day we were out cruising him in his camaro and me in mine. We got out on the highway and decided to see how fast his could get up to. Since his speedometer only went to 85 he followed me up to 115. Then we started to slow down and we started to get back into town and he decided to show off by breaking it loose going 40. Well after that he down shifted and suddenly it wouldn't go into any gear.
We got it trailered to his house the next day, and we got it up and checked out as much as we knew. And what do we find!? That the transmission is from a 5.0 camaro from 1984, But were not sure whats wrong we thing it might be the clutch, but the clutch is litterly brand new we even have the box. So maybe it need to be adjusted? Or it could be the shift fork?
We also found out the the drive shaft is an aftermarket aluminum one and it seems to be pulled back out of the transmission. So maybe the U-Joint? and i'm pretty sure the rear end is screwed up because when we spin the driveshaft by hand it doesn't spin the tires. Good thing he gave up a brand new rear end with it that has 3.73's in it.
Sorry for the story but do any of you guys have any advice? Any ideas why it wont go into gear. Some of my buddys say either shifting fork or input shaft, drive shaft. im just looking for ideas and advice please and thank you all .

 

Trans is probably shot. There is a reason GM never put a T5 behind the 350s in the F-bodies. You just found out why the hard way. The 10 bolt out back isn't all too great after some power either, especially behind a manual.

 

Your problem isn't with the u-joints or the rearend. It sounds like it's an open diff rearend, so your spider gears are going to blow if you keep up with that kind of abuse. Looks like his dad broke the trans, and you guys didn't help it any after that. Something was already wrong, which is why it was popping out of gear. You guys just made it worse. The T5 wasn't designed to take clutch dumps from behind a 350, and as Coco was getting at, wasn't put behind bigger than a 305 for a reason. I would drain the oil and see what comes out. If you get metal chunks coming out, it's time for a rebuild or replacement. At the very least, you need to do some exploratory surgery.

 

Alright guys thanks for the help. We looked into it a bit more this morning and were pretty sure that the drive shaft is for an automatic transmission. Also since the transmission is pretty much screwed were gonna drop the T5 and take a look in it and see how bad it really is.
Also my buddy is thinking of just going with an auto since it seems it would take to much to build that t5 to withstand the power, and we dont have a t-56 laying around to put into it. He has a 700R4 out of a 1994 silverado just sitting around and we were wondering if it would work? If it does should there be anything else we need to know before going about this conversion? Also we will be rebuilding the 700R4 because when he had it in the truck it did slip; So do any of you have any suggestions for some good rebuild kits?
Once again thank all of you guys for the help and such.

 

Too my knowledge, whether it was originally a stick or auto shouldn't matter as far as the driveshaft is concerned because I believe they used the same one.

A transmission out of a 94 K1500 (Silverados weren't around yet) won't work. It's a 4L60E transmission, meaning it's electronically controlled and requires a computer to use. Any thing from a 93 or older GM will work. The only thing I can think of that might need replaced is the trans crossmember when going with a 700R4/4L60 trans.

You could also bolt in a Turbo 350 or 400, both of which are relatively easy to come by and when built, are nearly bullet proof. That route, however, would certainly require a new crossmember and a custom driveshaft. You would also lose the benefits of overdrive, resulting in a few less mpgs.

Also forgive me for the technicality on the K1500/Silverado thing. I know they are essentially the same, but I'm kinda **** when it comes to proper usage of terms. Kinda like engine and motor or that the "W" on the oil bottle stands for winter, not weight.