Yoke play / Vibration

[sinny]

I've had a real bad vibration at over 60mph, so put the car on axle stands & ran it. I noticed the yoke was wiggling about where it enters the rear of the trans.
Shut it down & am able to shake it about. I've uploaded a video which isn't easy to see but you can hear it moving about.
Is this too much play? What's likely to be wrong? A worn bearing?

[Mick70RR]

There's always play like that in the slip yoke. It doesn't look to be into the gearbox enough to me, like the propshaft is too short.

[terryr]

was your car manual at one point ,as they have a longer gearbox ,that prop needs to be lengthend or you will bust your tailshaft,i would also say your bearing is shot in the tailshaft due to the prop being to short

[sinny]

I don't know if it was ever a manual but it is possible. This prop shaft was in the car when I bought it. What's the easiest way to sort this? New prop shaft?

Is it likely that this is the cause of the vibration? Here's a video showing the prop spinning.

[terryr]

yep ,will cause it ,may have taken out the bearing in the rear of the tailshaft ,which will make things a lot worse ,if I remember ,they are like a cam bearing ,one of the gearbox lads could tell you more ,just get the prop lengthend ,you only need about an inch to an inch and a half of the sliding part of the yolk clear of the oil seal ,I got my prop done by dave mac propshaft services in Coventry,cost about 175 all in ,that was with new bearings everything;;;if your car used to be manual it should have a hump on the driver side of the tunnel

[terryr]

just see the second vid ,you really need to get this done before you loose the front of the prop ,that can be nasty ,you cant have a lot of the yolk in the box atall


I don't think that balancer looking thing is normal for a b body either ,but im probably wrong ,none of the ones ive had have had that

[sinny]

Any idea how much should be in the tail?

[terryr]

all of it except for about an inch,you can see on your prop how much it moves in and out ,I normally go just over an inch from the start of the shoulder of the yolk ,it really does not take a lot to crack the tailshaft of the box,they normally go where the speedo drive goes in ,,some say push the prop all the way in and measure from the center of your u js on the prop and then subtract an inch from that

[sinny]

Cheers Terry.

[Guy]

The car may not have been a manual, but the propshaft may have been, as Tel says I have never seen a balancer on a Mopar prop before. I cant recommend Dave Mac propshafts high enough excellent service and top quality work

[Blue]

I have seen the balancer before on a few cars, not sure why it's there though. At a rough guess that prop is about 3" too short. To determine the correct length, measure from the end of the tail shaft (not the seal) to the centre of the rear UJ, subtract 3.5" and that's your correct front to rear UJ centre to centre length. I would replace the rear bush in the tail shaft while you are at it, you've not done it any favours.

[sinny]

Thanks guys, I'll try to find a local place if the one that Pete has doesn't work out. If not it'll be a day trip to Coventry!

[sinny]

Well finally got the new prop in & the yoke is nice & steady now but it hasn't made a single bit of difference to the vibration!

The vibration is light at 30mph then disappears until over 60 when it pulsates badly! Even does it when up on jack stands. What do you think? Torque converter?

[db]

Have you got the right flex plate & damper for the motor?
Check your motor mounts aren't coming apart ESPECIALLY the tailshaft mount. It may have taken a beating with the vibration from your tailshaft issue.

[sinny]

The flex plate & damper were both on the car when I got it so I'm not 100% sure.
The engine mounts are good, the trans tail has seen better days though. But the vibration is so intense I don't think that is the cause.