Bad vibes

-
Babyblue66

Babyblue66

Cool dude
Joined
Oct 29, 2007
Messages
878
Reaction score
401
Location
In an apartment, MN
65 Barracuda 273, 8 3/4 out of a 71 Duster, auto.

Stock trunion type shaft with new u-joint recently balanced. Vibrates like hell on acceleration, real bad when your on it hard, smooth on decel. Smooths out real nice at about 70mph.

Had a new shaft made with 2 joints and a slip yoke, brand new stuff, now nice and smooth on acceleration vibrates like hell at 70 and up, real bad.

This sucks.

Any suggestions on shaft angles or ideas.
 
Did you try a different axle shaft yet? That is weird. Sounds stupid but are your lug nuts tight? None of this happened before your 8 3/4 swap?
 
Babyblue66 said:
65 Barracuda 273, 8 3/4 out of a 71 Duster, auto.

Stock trunion type shaft with new u-joint recently balanced. Vibrates like hell on acceleration, real bad when your on it hard, smooth on decel. Smooths out real nice at about 70mph.

Had a new shaft made with 2 joints and a slip yoke, brand new stuff, now nice and smooth on acceleration vibrates like hell at 70 and up, real bad.

This sucks.

Any suggestions on shaft angles or ideas.
Click to expand...


You lost the old trunnion shaft and went with the new joints, flanges, stub slip style (better)

Sounds like it wasn't balanced with the flanges on and balanced on the joints....
 
Supershafts said:
You lost the old trunnion shaft and went with the new joints, flanges, stub slip style (better)

Sounds like it wasn't balanced with the flanges on and balanced on the joints....
Click to expand...

I sure does feel like a shaft way out of balance. I was charged 40 bucks for balancing though. I don't know how they do it, but I'd like to see their process. Not that I know better, but I know that many times **** just isn't done the way it should be.
 
Depends what machine they use.... Axi-line, Westport, Hines, Rockwell....etc..
You would hope they are using Axi-line/superflow or westport... the rest don't spin over 1000 rpm and they may not have the ability to balance shafts with flanges
 
Supershafts said:
Depends what machine they use.... Axi-line, Westport, Hines, Rockwell....etc..
You would hope they are using Axi-line/superflow or westport... the rest don't spin over 1000 rpm and they may not have the ability to balance shafts with flanges
Click to expand...

thanks, I'll check it out.
 
Got the shaft back and they said they changed the balance a little. Still ain't right. Vibes strt coming on bad at 72-73 mph and just get worse. Really bad at 80. I can even feel it a little around 45-50, then smoothes out a little at about 65. Buts always there.

I don't know what to do at this point. A 280.00 shaft and its worse than before at highway speed, but much better under low speed acceleration.

Could u joint angles cause this?
 
Angles can cause vibrations....

Here is how it works...

Normally in a street app you can run up to 5 degrees on the angle without issues, since 5 degrees is good for 3000 rpm....

Most street vehicles shafts aren't at 3000 rpm at highway speeds.

Now as speed increases angles need to decrease for 2 reasons..
1. the joint will over oscillate and cause vibrations and premature wear and possible failure.
2. in the performance world any angle more then 0 is a hp loss.

So at 70 mph what is your rpm in 1 to 1 ?
What is the shafts angle ?
what is the pinions angle ?
what is the trans angle ?

It sounds like the issue might be with the balancing machine... Some balancing machines do not spin fast enough rpm... hines machines spin at like 700 rpm... not good..great for pto shafts, not good for cars and trucks...
 
I had it checked at another shop. It was off and the stub had some run out. Its a lot better, but still not gone. Another 66 bucks, and still have an issue. I'm ready to find an original shaft put the 7 1/4 back in and start over. When I got the car I could do 80mph all day and had no vibes. This sucks!
 
Is the 8 3/4 a s.g?Maybe clutches are worn or cone is worn causeing vibrations?Did you swap gears in the chunk?The vibrations might be related to the rear instead of the shaft?worn bearings?Just a thought.
 
Is there a lot of play, now by play i mean you take the outer housing and twist it opposite of the shaft and it has movement ?

also check for up and down, hold the outer housing on the floor or leave it bolted in the car and see if you can move the shaft closer to the shaft tunnel and pull it closer to the ground...

If you have what is clearly a lot of movement in both those tests then balancing will only make it a little better, if at all since the play will effect the balancing, if they noticed that they should have recommended below ...
You can have the shaft changed to a LD style which uses a flange yoke, 1310 joint, slip yoke and stub shaft...and leave all that trunnion stuff behind
 
i am having the same problem at 70 get bad vibration that gets worse as i go higher , Dif was taken apart and everything looked good . I can't figure this out either . Gears bearings and axles are all in perfect shape , new joints . Will try to rebalance shaft .
Be interested if you find out what the cause is , might be same in my car
 
You must log in or register to reply here.
-

Back
Top