Vibration at certian speeds

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BroncoJim
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Vibration at certian speeds

Post by BroncoJim » Sat Mar 14, 2015 11:00 am

Hey Gang,
I picked up a bad vibration at 33 mph and at freeway speeds. I had the balance checked on the wheels and they are fine. The u-joints seem OK and it it does not vibrate at idle or at speeds below 30 MPH. What could be causing this?
TIA,
Jim
Jim
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Tom Dummer
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Post by Tom Dummer » Sat Mar 14, 2015 7:33 pm

How did you check the ujoints? I've had them feel fine until I pulled the driveline out and checked them on a bench
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Post by BroncoJim » Sun Mar 15, 2015 7:24 am

I crawled underneath and checked for looseness or clunking. No good?
Would u-joints show up as a vibration at only certian speeds? It begins at 30-33 and lessens at higher speed but never completely goes away.
These U-joints are probably 15 yrs old with about 60K on them.
Jim
1976 Bronco, 351W, C4, 4.11s, 2 1/2 BC Broncos lift, 33's, 3G. 24 years and it's almost done.
1965 Mustang 5.0 SEFI, T5 lotsa fun...
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Tom Dummer
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Post by Tom Dummer » Sun Mar 15, 2015 8:48 am

It doesn't take much to drop a driveline. Take it out , clean off a spot on the bench barely big enough for the driveline. Oh, wait, that my garage. Take each ujoint and check it for looseness or play. How long ago did this start? And after a hard wheeling trip? I've shredded the driveline balance plates off the driveline but that was because I was stuck on a rock pile with the determination to rip myself free.
Most vibrations that come & go at different rpms tend to be from ujoints going away, you just have to find it..
Another one is having a driveline slip yoke put together out-of-phase, as in the yokes at each end don't line up correctly. That vibration comes in and stays at most all speeds.
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Post by nvrstuk » Sun Mar 15, 2015 9:08 am

x2 what Tom said... could be your CV joint too.
Strrrroker... 418 cubes, 518HP, SEFI Trick Flow, what, no distributor??? EDIS, burping the throttle is a whole new experience... :)

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Post by BroncoJim » Sun Mar 15, 2015 9:16 am

Tom Dummer wrote: clean off a spot on the bench barely big enough for the driveline. Oh, wait, that my garage.
LOl That's my garage too.

I just noticed it right after I had the tires swapped which led me to believe it was in the balancing. But I had all four re-balanced at a reputable shop. I'll yank the driveshaft and check it. Would it be worth it to have the driveshaft checked for balance? it is the stock DS but the vehicle has not been wheeled hard since the mid 90's.
Jim
1976 Bronco, 351W, C4, 4.11s, 2 1/2 BC Broncos lift, 33's, 3G. 24 years and it's almost done.
1965 Mustang 5.0 SEFI, T5 lotsa fun...
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Stan
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Post by Stan » Sun Mar 15, 2015 10:56 am

nvrstuk wrote:x2 what Tom said... could be your CV joint too.
What those two guys said ! :)
Doing some research on these things- when they were new the #1 maintenance {warranty} complaint was with the CV joint.
Stan
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Tom Dummer
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Post by Tom Dummer » Sun Mar 15, 2015 11:47 am

I wouldn't go after driveline balance until after all the U-joints have been checked and/ or replaced.,
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Post by BroncoJim » Sun Mar 15, 2015 12:13 pm

Tom Dummer wrote:I wouldn't go after driveline balance until after all the U-joints have been checked and/ or replaced.,
yeah, I was thinking while it was out anyway. Probably why all my projects snowball out of control :D
Jim
1976 Bronco, 351W, C4, 4.11s, 2 1/2 BC Broncos lift, 33's, 3G. 24 years and it's almost done.
1965 Mustang 5.0 SEFI, T5 lotsa fun...
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Post by nvrstuk » Sun Mar 15, 2015 1:37 pm

HOLD IT!!! Didn't notice it till "after" the new tires or old tires were re-mounted?? Are you 100% positive of that? If so, then you could very well have a tire with a broken ply or belt in it... yup, when you're 147 yrs old like me all this stuff has happened to ya.

Move the front tires to back and back to front and see if the vibration changes or feels different. You will notice a difference if it's a bad tire...

Another thing you can do is pull the rear driveline and drive in front drive only. This will eliminate the rear driveline as the potential culprit.

BTW, notice how much torque steer you'll get in front wheel drive, especially with a non-selectable locker up front. :)
Strrrroker... 418 cubes, 518HP, SEFI Trick Flow, what, no distributor??? EDIS, burping the throttle is a whole new experience... :)

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Post by Tom Dummer » Sun Mar 15, 2015 5:26 pm

I learned long ago the differences in tire balance/ shakes. if your steering wheel shakes up & down, you'll find the out-of-balance at the rear, if it shakes left to right, it will most likely be one of the fronts.
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Post by Stock 68 » Fri Mar 20, 2015 4:41 pm

Interesting that Tom seems to know all the ways to tear shit up
Y'all are a buncha modifiers

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Post by Tom Dummer » Fri Mar 20, 2015 7:37 pm

If it can be broke, I probably have.
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Post by BroncoJim » Sun Mar 22, 2015 4:14 pm

I may have figured this out.
The alignment place that re-balanced the tires put the weights too much inboard and they were wiped out by the brake caliper.
Image

I am going to take it back to the alignment shop Saturday. Hopefully that will fix it.
Jim
1976 Bronco, 351W, C4, 4.11s, 2 1/2 BC Broncos lift, 33's, 3G. 24 years and it's almost done.
1965 Mustang 5.0 SEFI, T5 lotsa fun...
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Stan
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Post by Stan » Sun Mar 22, 2015 4:59 pm

Great - always good when you figure out a fix.
When you come to a fork in the road - take it
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Post by nvrstuk » Sun Mar 22, 2015 9:05 pm

So I was right...it was the tire... lol
Strrrroker... 418 cubes, 518HP, SEFI Trick Flow, what, no distributor??? EDIS, burping the throttle is a whole new experience... :)

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Post by BroncoJim » Tue Mar 31, 2015 4:09 am

Picked it up from the alignment shop on Saturday. The Tech assured me the tires were balanced to zero. It is better but there is a distinct vibration at around 33 mph. At freeway speeds it gets worse as you nudge towards 65.
Not sure where to go from here.
Jim
1976 Bronco, 351W, C4, 4.11s, 2 1/2 BC Broncos lift, 33's, 3G. 24 years and it's almost done.
1965 Mustang 5.0 SEFI, T5 lotsa fun...
"If you didn't build it, it's not really yours"

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Stan
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Post by Stan » Tue Mar 31, 2015 7:46 am

Did you try some of the stuff the "147 year old guy" mentioned ? Tire issues can do some weird stuff - wobble at certain speeds , pull one way or other just to name - 2 - LOL
Stan
hope you figure it out - mine has developed a vibration at about 60 mph - goes away at 70 - I'm thinking - only change has been tire wear.
Last edited by Stan on Wed Apr 01, 2015 7:41 am, edited 1 time in total.
When you come to a fork in the road - take it
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Post by BroncoJim » Wed Apr 01, 2015 3:56 am

Stan wrote:Did you try some of the stuff the "147 year old guy" mentioned ?
No, not yet. My daily driver has been down as well so I have been dealing with that. I can't swap the wheels front to back due to the tie rod rubbing on the rear rims. These are old aluminum slot mags.

Would a bent rim show up when they went to balance it?

I'll take the DS off this weekend and try it in front wheel drive only.
Jim
1976 Bronco, 351W, C4, 4.11s, 2 1/2 BC Broncos lift, 33's, 3G. 24 years and it's almost done.
1965 Mustang 5.0 SEFI, T5 lotsa fun...
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Stan
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Post by Stan » Wed Apr 01, 2015 7:43 am

I would think a bent wheel would show up especially with the "spin balancers". Maybe not as much if the wheel is bent or tweaked at the center/around the lug holes ????
When you come to a fork in the road - take it
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Post by 69brightbluebronco » Sat Apr 04, 2015 7:30 am

did they check the road force on the tires? this is different then balance.
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Post by BroncoJim » Sat Apr 04, 2015 1:17 pm

69brightbluebronco wrote:did they check the road force on the tires? this is different then balance.
No. What is that?
Jim
1976 Bronco, 351W, C4, 4.11s, 2 1/2 BC Broncos lift, 33's, 3G. 24 years and it's almost done.
1965 Mustang 5.0 SEFI, T5 lotsa fun...
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Post by 69brightbluebronco » Sun Apr 05, 2015 6:12 pm

not sure how to define it exactly, but i think related to the internal balance of the tires. usually high road force shows up in a tire with an internal defect, big mud tires. etc.
Kyle
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Post by DirtDonk » Wed May 27, 2015 9:14 pm

The tire balancing machine places a rolling load right on the tire tread itself just to simulate the load it sees when rolling between the road and the weight of a vehicle.
When they do this, odd things show up that would not be seen by simply looking at the "balance" as it rotates. This will highlight defects in the tire and actually provide a more accurate balance even on tires that are otherwise perfect.

In other words, I'm not really sure how to define it either!

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