There's a bushing at the end of the tailshaft where the slipyoke spins. My transmision is an A745 3 spped manual in a 69 Valiant. How common is it that they wear out, how the hell do ya get it out if it's worn and could that be the cause of some vibration? I had taken my driveshaft out previously to have it balanced and checked while trying to remedy this vibration issue and the slipyoke was shot/worn where it slips into the tailshaft making me question these bushings. They balanced my driveshaft and it seemed to help the vibration, but it seems to be creeping back. What do ya think? Any ideas? Thanks guys!!!!!!!!!!!!!

Yes a worn bushing can cause a vibration. I my memory is correct you have to pull the tailshaft to replace the bushing. Another possible cause is a bent or twisted shaft. The driveshaft shop you dealt with should have noticed such a defect but they may have missed it. Is the driveshaft the proper one for your application. Too long or too short can cause a vibration. Is the rear u-joint the proper one for the rear diff.

What about your pinion angle? That can also be a major cause of vibration.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

as far as I know the driveshaft id the correct one and the ujoints are correct. I had it worked on , balanced and new ujoints intalled. It seemed to smooth out the vibration for a few days, but it crept back. I don't know. This is driving me insane.

Also, I haven't done anything else that I think would affect the pinion angle. You'd have to mess with the rear axle to mess that up, right?

worn tailshaft bushings can cause a vibration as mcnoople states, but also a leaky seal. improper driveshaft angles can cause the tailshaft bushing to wear quickly as well as stressing u-joints and driveshaft yokes.
screwy pinion angles can be caused by a bad trans mount or worn rear springs/spring bushings. if the trans mount has been replaced, perhaps there were rectangular shims between the mount and trans that were not re-installed or the mount was a crappy replacement part that raised or lowered the trans a tad. whatever the cause, the pinion angle is worth checking. i have heard the miller factory tool was cheap and easy to use. also the service manual gives the procedure. IIRC frank adkins' book "mopar perfomance upgrades" (or a similar name) gives a low-buck approach to making a tool and taking the measurements.
as for bushing replacement, i don't have a service manual that covers a '69 valiant or 745 trans, but i also agree that the tailhousing must come off and the bushing be pressed out and probably staked when in position. what is required to pull the tailhousing i do not know.

-james

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I haven't changed the trans mount, but it might not be a bad idea. Another thing is that this vibration starts at 60mph exactly. Before that it's smooth as silk. Would these reasons ie bushing and pinion angle cause the vibration starting at this speed or would it vibrate at lower speed also? Thanks for the ideas!!!!!!

That sounds exactly like what Lurch (my '82 D150) does. I've been meaning to try changing the tailshaft bushing, too. Lurch also has a leaky rear seal and was run with the wrong driveshaft (about 1.5" too short, probably for a truck with a 9.25 instead of my 8.25) for who knows how long. Changing to the correct length driveshaft helped, but being run with the slip yoke too far back couldn't have been good for that bushing.
I bet that's where my bad vibes are coming from too, as I've swapped out the rear end (for other reasons) and that didn't change the vibration either.

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Brian (Valianator)

'65 Valiant V100 170/T-flite
'82 D150 225/4-speed
'65 Dart 225 4 door
'68 Dart 225 4-door with Valiant front clip (future project)

Anyone else out there have this issue? I've been trying to run this down for a while and it's seriously wigged me out. I'm at the point right now where I'm actually considering giving this problem to an actual mechanic. I hate doing that and haven't had to in a really long time. My first job was as a parts guy at NAPA. I started as a driver and after the crap I saw so called profesional mechanics do to peoples cars, I learned how to work on my own car. I won't even let one of those guys get in my car unless they come highly recommended and right now I'm new to this area and don't know any. Well enough babble. Anyone else have this problem with the tailshaft bushing being the possible culprit? Also, would anyone know where the hell I could even find a new one? I've been looking and noone I can find has hardly anything available for my A745 manual trans. Anyone? Thanks guys!!!!!!!!!!!!!!!!!!!!!!!!!!