Vibration

[50fordcoupeman]

My avatar has a 302 coupled to what I believe (by casting numbers) to be a 68 Galaxie manual 3 speed (no OD). There is a very slight vibration but it goes away when clutch is depressed or coasting out of gear. The drive shaft appears to have been balanced and the u-joints are new. There is no play from the tail shaft but there is some play from the yoke when it is slid onto the tail shaft. My question: is there a bushing/bearing that the yoke slides through or does the yoke need to be replaced? It didn't look to me that the yoke slid through anything except a seal.

Thanks for any suggestions.

[40 Deluxe]

Yes, there IS a bushing on the other side of that seal. There should be very little up and down play in the yoke. This was a very common wear point back in the day. There were special tools made to replace that bushing without pulling the extension housing off. Make sure your yoke is not worn. The outer diameter should be smooth, no scoring.

[50fordcoupeman]

Thanks 40!! The yoke looks pretty good and not scored. Appreciate the help and your knowledge.

[Daves55Sedan]

Noting that this drivetrain is not original to the car, I suspect the driveshaft was either modified or a completely different driveshaft was used. It is possible that the driveshaft is shorter than it should be which means that the front yoke might not have as much meat coupled with the tailshaft. The yoke needs to slide in far enough to gain good engagement with the tailshaft splines AT THE FRONT OF THE YOKE. If it is too short, the driveshaft will slop around even if the driveshaft is properly balanced.
Notice how the pipe portion of the yoke is 5 or 6 inches long and there should only be about 1-1/2 inches at most sticking out from the back of the rear extension housing, that means the yoke would be engaged about 4-1/2 inches in the tailshaft. That would be a good assembly. Also notice that that bushing inside the tailshaft is about 2 inches long. You want the front of the yoke pushed past the front of that bushing.
This should all be checked WHILE THE REAR AXLE OF THE CAR IS IN IT'S NORMAL POSITION RELATIVE TO THE HEIGHT OF THE CAR FRAME.

[50fordcoupeman]

Thanks Dave. Yes you are correct on the driveshaft. By observation I suspect the front end of the driveshaft was modified. I will check again to see how much is sticking out. If I remember correctly the pipe part of the yoke slid in almost flush with external part of the seal.
Thanks again!!

[bobss396]

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With the car on a flat level surface, all 4 wheels on the ground, I like to have 1" of exposed yoke hanging out of the transmission. This is how I measure up for a new driveshaft and it works for me.

[Daves55Sedan]

Originally Posted by bobss396

With the car on a flat level surface, all 4 wheels on the ground, I like to have 1" of exposed yoke hanging out of the transmission.

I believe I mentioned 1-1/2 inch at most, but I am going to agree with bobss396. I looked under my '55 car and it is about 1 inch. The main thing is that you have a lot of meat engaged between front yoke and tailshaft.

[50fordcoupeman]

Thanks for all the info guys. There is 1 3/8" sticking out of the tail shaft housing and the dust shield is almost touching the front of the u-joint housing. So as 40 Deluxe has said I think it is time for a yoke new bushing.