High speed Vibration - tailshaft bushing question

[70Bronco]

I've been chasing a high speed vibration--it starts about 60 mph and stays there up to 80 mph. If you throw it in neutral at that speed, the vibration stays. New tires, all balanced, rebuilt front end and aligned. Transmission mount was toast and has been replaced. Vibration remains.
I pulled the drive shaft and inspected it. Shaft looks good. Both U-joints are good.
The transmission tailshaft has play in it, probably more than it should have.

• I'm thinking new tailshaft bushing and a new seal might solve my problem. Anything else I should inspect while I'm there?
  
• I do not have a special bushing remover tool--if I remove the extension housing, will the tailshaft bushing come off without special tools?

 

[PurpleBeeper]

Automatic, 4 spd or ?
I would also consider re-balancing the tires...a weight may have fallen off & consider balancing the driveshaft. I read somewhere that a guy was marking his driveshaft & installing a large hose clamp...drive & compare vibration, move hose clamp 90-degrees & repeat, just to see if it indeed was a driveshaft balance issue.
Hope this helps

 

[70Bronco]

Automatic, 4 spd or ?
I would also consider re-balancing the tires...a weight may have fallen off & consider balancing the driveshaft. I read somewhere that a guy was marking his driveshaft & installing a large hose clamp...drive & compare vibration, move hose clamp 90-degrees & repeat, just to see if it indeed was a driveshaft balance issue.
Hope this helps

1966 Belvedere II 361, 727 automatic.

 

[Fran Blacker]

Here's the tool for a 727 or a manual trans. Don't think fits a 904 trans

 

[70Bronco]

Here's the tool for a 727 or a manual trans. Don't think fits a 904 transView attachment 638633

Is that tool required if I remove the extension housing on the car?

 

[Fran Blacker]

1966 Belvedere II 361, 727 automatic.

I would consider renting the tool if you do change the bushing. $130 in P/P will Return $100 if you return tool in good condition.
A favor you can do me is measure the center to center of u-joints if your sure it's the original driveshaft. Had a dana in my 66 Satellite for years. I switched back to an 8.75 rear but I have 2 drive shafts for 8.75 rears. One is an inch longer than the other and I don't know which is correct for sure. The online chart aren't that correct. They say Dodge and Plymouth are the same length, Dodge has a 1" longer wheelbase.

 

[70Bronco]

I would consider renting the tool if you do change the bushing. $130 in P/P will Return $100 if you return tool in good condition.
A favor you can do me is measure the center to center of u-joints if your sure it's the original driveshaft. Had a dana in my 66 Satellite for years. I switched back to an 8.75 rear but I have 2 drive shafts for 8.75 rears. One is an inch longer than the other and I don't know which is correct for sure. The online chart aren't that correct. They say Dodge and Plymouth are the same length, Dodge has a 1" longer wheelbase.

U joint Center to center is 51”.

 

[Fran Blacker]

Is that tool required if I remove the extension housing on the car?

Probably not. When I pulled mine it made a pretty good bang when it came loose. If you remove tail shaft housing a trans shop could do it cheap. They wanted $90 to do mine but I have a H-pipe and it would be hot when got there. Its tight and wasn't sure if they could do it without dropping the pipe.

 

[Bill Monk]

I had a 68 Barracuda that just about drove me nuts, I finally had the driveshaft balanced and it cured the problem. Not saying that's your problem but that's what mine was

 

[Fran Blacker]

Had .010 to .013 play in bushing I removed. The drive shaft I used with the Dana was to short. At 65 to 70 mph 3.54 gears it would rattle.

 

[Fran Blacker]

As Bill Monk said check the shaft the weights have 2 spot welds. Look carefully see if one broke off.

 

[400sforever]

My 74 and 73 chargers boTh had to have their driveshafts balanced. I bet that's the issue. Had the same vibration with both cars

 

[70Bronco]

As Bill Monk said check the shaft the weights have 2 spot welds. Look carefully see if one broke off.

Yep, both weights are still on it and completely intact.

 

[747mopar]

I replaced my tailshaft bushing without a special tool but I do have a press, make sure to line up the hole for lubrication. As others have said check the tires and shaft. It seams to be more and more common to get broken cords in tires too although that likely wouldn't be speed sensitive. Sounds to me that it's in the shaft somewhere rather it's the bushing, bent or out of balance.

 

[BSB67]

I've chased after a similar problem. Changed a bunch of stuff including the bushing. In the end, it was the driveshaft that looked fine.

 

[70Bronco]

I've chased after a similar problem. Changed a bunch of stuff including the bushing. In the end, it was the driveshaft that looked fine.

Yeah, I’m leaning toward having it checked. It’s easy enough to remove.

 

[1967coronet]

One thing I found in my vibration search is to replace the slip yoke itself along with the bushing.
The bushing change will help but to really snug things up swap to a new slip yoke.
They wear inside around the splines more than you think.

 

[Those]

I chased what I called a front end vibration for 5 years but it was more like a front end bounce. Everything was new up front. Borrowed and tried 3 sets of front tires with no improvement. It would start at 65 mph and stay. Last week I lowered the torsion bar adjusting bolts 3 turns and dropped the front 1 inch. Rides great now, no more vibration or bounce.

 

[wyrmrider]

and if you change your u-joints mark the yokes and shaft and get them back together the same way- but if they have been apart before hard to know
also only use OEM Mother Mopar brand or genuine Dana Spicer
they are the only readily available ones that are deep case hardened heat treat others are flame "hardened" surface only or induction "hardened"
they brinnel and fail per Murphy's law
so balance and check your pinion angle if everything else checks out

 

[70Bronco]

UPDATE:
Took the drive shaft in to be re-balanced. U-joints are good. Spline is good. Balance was off a little bit. They moved the front weight and the shop said it was running smooth on the machine. Put it on the car--it's running smoother below 60 (I thought it was good before), but the 60+ mph vibration is still there.

I don't want to spend time or money replacing the tailshaft bushing if that's not a likely culprit. Maybe I'll go back to wheels, tires, and brakes. Brakes are new, but I don't think the drums are. No vibration when stopping hard. Tires are new and have been balanced twice. Maybe a wheel is a little bit out of round. Front end has been completely rebuilt.