The vibzzz are killin me!

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Cravin'sCuda

Cravin'sCuda

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Maybe you guys can help me with this vibration and cannot seem to find. I have a 67 barracuda with a 410 stroker, 727, 8-3/4 rear with 2.94 gears and 17" wheels. I have a vibe at approx 60-70 mph@2600-3000 rpm. I recently rebuilt the engine so Im thinkin oh crap. It does not vibe in park or neutral at those rpm ranges, so i figure im cool. I had the tires balanced, no go. I replaced the iso driveshaft with new and u-joints, no go. I put the rear on jack stands and ran it and can feel the vibe. I pulled the wheels and its still there. Pulled the brake drums and its still there. I pulled an axle from one side and still there. I pulled the axle from the other side and its still there. I figure okay I'm down the the extension housing bushing.:sad: The trans was rebuilt approx 9k miles ago along with the rear diff. This last weekend I removed the extension housing and measured the bushing and didnt seem to be much different than the new one but showed wear and I changed it out. I put it all together and its still there. The vibe is kind of a come and go-you can almost time its frequency. I'm at a loss, from this point its going to start to get expensive.:banghead: any help would be much appreciated, Thanks.
 
If it is an oscillating vibration, almost sounding like a buzz, it still could be pinion or trans angle. If it feels like a wobble it's a wheel or tire. sounds like you did some good tests. there are threads here about pinion angle that can help.
 
Have you had the drive shaft checked for bent, excessive run out, out of balance?
 
Start taping fender washers to driveshaft. Do one and see if it does anything. Move in 90 degree increments until you feel a difference. You can use a large hose clamp too. I thought I read somewhere it would find its own balance if you didn't tighten real hard, sort of let it rotate stiffly. Or drill and pour a quart of atf into the drive shaft and weld back up. Sounds strange but its also supposed to calm harmonics (TCI rattler balancer comes to mind) . Never tried the fluid...but the taped weights was how the drive shaft guy did mine until it balanced then he tacked them on.
 
The car is in a small garage with a slight slope to it and I havent any access to a lift. I have tried to check the pinion angle the best I can with the car on the ground, thats a no go a little to much gordo going on here. I put the car on dollies and try checking it, i figure the slope in the garage is a constant. Its a real pain to see the trans side but with the calcs I came up with I added a 1 degree down to the rear end and nothing changed. Ive used the regular protractor and the inclinometer for the iphone (a little sensitive). and nothing has changed. It is like a buzz, I figured that with the replacement shaft i could rule that one out. Thanks.
 
I have this exact same problem. Car did this with the old 318 engine and is still there with a new 360 engine. I've also had the entire rear end apart, with the exception of the carrier and pinion bearings. Axles are new with new bearings. Im going to pull my driveshaft and have it balanced to see if it eliminates the problem. Im stumped as well!! I wish you luck and post up if you figure out what it may be.
 
Sounds like unbalanced drive shaft to me. It don't cost much to have it checked at a machine shop.
 
Before you take drive shaft to machine shop try flipping the back by the rear end 180 degree. My machine shop say rebalance shaft any time you change u-joints, I think they charge like 8 dollars to bal.
 
tekslk said:
Before you take drive shaft to machine shop try flipping the back by the rear end 180 degree. My machine shop say rebalance shaft any time you change u-joints, I think they charge like 8 dollars to bal.
Click to expand...

Curious but what difference would that make?
 
straightlinespeed said:
Curious but what difference would that make?
Click to expand...

Yokes are not perfectly balanced.
Ever change the front one 180?
They should always be put back in the same orientation when ujoints are changed.
Seems like not many people know that.

I had a nasty vibration in the driveline, and one day just for the heck of it I pulled the driveline and swapped the front yoke 180 and the vibration was really close to gone.

The reason I swapped it was because the ujoints were new when I got the car, and I suspected the driveline may not have been assembled correctly.
Turned out I was right.
 
TrailBeast said:
Yokes are not perfectly balanced.
Ever change the front one 180?
They should always be put back in the same orientation when ujoints are changed.
Seems like not many people know that.

I had a nasty vibration in the driveline, and one day just for the heck of it I pulled the driveline and swapped the front yoke 180 and the vibration was really close to gone.

The reason I swapped it was because the ujoints were new when I got the car, and I suspected the driveline may not have been assembled correctly.
Turned out I was right.
Click to expand...

Ahhh Thank you Grass Hopper! Previous owner also installed new ujoints before I bought it. That might be worth a shot for both of us?!?!
 
straightlinespeed said:
Ahhh Thank you Grass Hopper! Previous owner also installed new ujoints before I bought it. That might be worth a shot for both of us?!?!
Click to expand...

It very well could be the problem then, but you have to change it to find out.

Took me about 30 min to take the driveline out and swap the yoke around, then put it back.

Run the engine for a couple of seconds right before you take the driveline out and you will loose less fluid out of the trans. :-D
 
I was taught that any time the front yoke is separated from the shaft ( replacing U joint ) mark the parts first. I got into the habit of marking everything. If I pull rotors or drums I write on the right ( my method to the madness ).
Fat yellow crayon in my toolbox is worn to a nub. Was all this coloring necessary ? I'll never know.
 
TrailBeast said:
Yokes are not perfectly balanced.
Ever change the front one 180?
They should always be put back in the same orientation when ujoints are changed.
Seems like not many people know that.

I had a nasty vibration in the driveline, and one day just for the heck of it I pulled the driveline and swapped the front yoke 180 and the vibration was really close to gone.

The reason I swapped it was because the ujoints were new when I got the car, and I suspected the driveline may not have been assembled correctly.
Turned out I was right.
Click to expand...

This, as stated most people don't, even the Haynes manuals will tell you to do this.
 
The idea of turning the shaft in the end yoke would only work if the shaft was assembled using the diff and oriented that way, otherwise and which i can guarantee it is not assembled that way so it would make no difference.

That only works at the slip yoke since the shaft is atleast balanced as an assembly and the slip yoke is a part of that process, some companies assemble on fixtures and then add joints and other coupling parts and then balance the assembly, some do it with all the corresponding pieces.

When ever you change joints everything should be oriented the same, but even changing joints can put the shaft out of balance.

What Cravin described points to a shaft issue, and with the 2.9 ratio that is where it would show up
 
Supershafts said:
The idea of turning the shaft in the end yoke would only work if the shaft was assembled using the diff and oriented that way, otherwise and which i can guarantee it is not assembled that way so it would make no difference.

That only works at the slip yoke since the shaft is atleast balanced as an assembly and the slip yoke is a part of that process, some companies assemble on fixtures and then add joints and other coupling parts and then balance the assembly, some do it with all the corresponding pieces.

When ever you change joints everything should be oriented the same, but even changing joints can put the shaft out of balance.

What Cravin described points to a shaft issue, and with the 2.9 ratio that is where it would show up
Click to expand...

Exactly, probably pointless but it couldn't hurt to try it since it's so easy to do.
 
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