aemlet

My dad and I just rebuilt the top & bottom this engine. The head gasket cracked & was pushing coolant out through the overflow. Everything was working beautiful for about 10k miles, now the vehicle is having difficulty climbing hills and the transmission is acting funny. The first issue I noticed was the transmission felt like it was clunking into reverse, and it seemed slow actually engaging when put into drive. It still seemed to work fine though. I have an hour commute to work, and I climb 2 mountains (hills to those folks out west....we're talking 1500' elevation). During these climbs is when I began to notice that I was having trouble maintaining speed. I needed more throttle. However it's gotten worse. Now there is a crazy noise accompanying this lack of power. When the engine hits about 3500+ RPM it sounds like a propeller plane under the hood. This happens when it is in 3rd gear, I believe.....when it shifts to 4th, it goes away....the shift is relatively hard & when the sound goes away it almost sounds like a blow off valve releasing.
I changed the fluid and drove it around to see if that helped (didn't think it would)....it did not, and now the car seems to stutter when it takes off, and sort of surges up and down while applying light throttle.
Is this a torque converter issue, or is this clutch issues? The noise is crazy. I've never heard such a noise. I figured the transmission needs an overhaul, but this behavior is a bit bizarre.
Any thoughts?

aemlet

I thought I'd post an update. As I indicated in my post I was pretty sure this was a transmission problem. I was wrong. After thinking and test driving and thinking and tinkering, I just could not believe it to be a transmission problem. Logically it just didn't seem to make sense with the symptoms. Since the fuel pump, pressure regulator & filter were all originals, I thought maybe fuel pressure could be an issue. Installed a gauge to test. Not a problem....So my father thought that perhaps the exhaust was blocked. I disconnected the exhaust at the header, and viola! I had power again! Shifting was smooth!
To investigate further I disconnected the flange just behind the catalytic converter and re-connected it at the header, and the problem returned. So the problem turned out to be the catalytic converter. I have one on order and should be here by mid week.
What a relief. I really thought I had a bigger problem. Plus this was all happening with no codes being thrown. Just thought I'd update just in case someone has a similar issue. By the lack of responses I'd say no one has quite experienced this exact issue.