Bad Vibration at highway speeds

[Rancheroboy]

Hi All

I have a 57 Ranchero with 292, 3 speed manual O/D, all stock.  I have always had a vibration when coasting at highway speed. Had the transmission overhauled in 2003 which helped a little. At that time it was found that the pilot bearing in the flywheel was the wrong one and so the shaft was not tight and the front trans bearing was pretty worn. This fix helped a bit but not completely.  Now the vibration has gotten much worse. Rotated tires, not that, took it to a local drive line shop that straightened and balanced the drive shaft, new rear yoke, 2 new u-joints, new trans tail shaft bushing/seal, new diff seal, and they tried shims to change the drive shaft angle from 5 degrees to 2 degrees. Took the shims out, back to 5 degrees. Nothing helped and it seems even worse.  Another  problem that has started is it sometimes does not shift out of OD at and stop unless I pull the OD cable to manually take it out of OD. When I start out in this condition there is a huge crash as it automatically jumps out of OD.  I am thinking there is a problem with the tail shaft in the trans or the rear trans housing bearing is bad.  I have an appointment next week to pull the trans.  Any thoughts on this bad vibration. Happens mostly while coasting but it is always there.  Thanks for any suggestions

[thomasso]

Did your rebuilder disassemble and inspect your overdrive unit also?  Be sure to check the maim shaft for runout.   Your OD engagement pawl is not disengaging.  Governor points could be sticking, Solenoid spring could be weak or broken or the plunger gummed up. Or the pawl and related parts bad.  Upon complete disassembly and inspection problems should show themselves.