Just finished installing an A518 46RH transmission into my 74 Challenger with 360 LA engine. It is a 92 model with the locking torque converter and is hydraulic. Before installing took the time to "freshen" the transmission by putting in an overhaul kit for the seals and clutchpacks. All looked great inside. During the overhaul i left the governor untouched. I also put in a transgo shift improver kit and a new locking torque converter. This is my second overhaul as i successfully overhauled the old 904 torqueflite that was in the car. I plan on just using toggle switches to activate the locking torque converter and overdrive engagement. I was careful adjusting the throttle rod so that at wide open throttle, it would push the lever nearly to the end. After putting in 8 qts of tranny fluid, started the engine and checked for leaks... didnt see any, so put it in neutral to activate the pump and let it warm up. Checked dip stick and it wasn't showing anything so put in another qt and then it was showing, so added another and that got it pretty close to the "cold" mark on dipstick. Put it into reverse and it engaged, then into drive and it engaged. Great, so with it warmed up took for test drive, but no shifting at all, all the way up to 4,000 rpm and no shift ...stuck in first. Now, when i back off to let it low down, it goes into neutral, with no propulsion, tach goes to idle.. Then when car slows down to under 10 mph, it reengages 1st gear, and i was able to drive it home. Rechecked the fluid level in neutral now that it is fully hot, and added a little more...now has about 10+ qts in it. Did another drive and same thing... i start out in first and it never shifts. Doesnt matter if i pull the shift lever to D or 2 or 1...it acts the same. Any transmission guru's that can give me probable problems? I'm thinking most probable is to pull the valve body and go over it... This i can do while transmission is still in the car. Ive also heard that this can be from a "stuck" governor in the tail section, or that in reassembly from my overhaul that the "tubes" might have gotten bent. If that is the case, can i pull the tail section while it is still in the car...or... Suggestions please !!