Two weeks ago, I installed an M-41 onto my 74 144. On jackstands, everything worked well, including the overdrive. When all the work was complete and I took the car off the stands, and took it for a test drive. All the gears engaged smoothly, including reverse, and the O/D worked flawlessly. It was a joy indeed to hit the switch and cruise on the interstate with more relaxed engine revs.

Now the problem. In second and third gears ONLY, the tranny makes a loud humming sound, especially when you are on the gas, and you can feel a lot of vibrations coming through the shifter. Also, in overdrive, I could barely hit 60mph as the driveline vibrations are very bad. I am ready to pull the tranny out again and have a look. Any suggestions on what might be wrong? Thank you in advance. If it makes it any clearer, these problems never existed on the original M-40, and all the U-Joints are OK.
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...and the bricks keep on rolling