Bus Conversions dot Com Bulletin Board
July 23, 2014, 03:11:39 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
News: If your computer is lost, damaged, or stolen, we will replace all of your E-Mags for free.
   Home   Help Forum Rules Search Calendar Login Register BCM Home Page Contact BCM  
Pages: [1] 2  All   Go Down
  Print  
Author Topic: vibration at speed !  (Read 1476 times)
sledhead
Sr. Member
****
Online Online

Posts: 338





Ignore
« on: October 12, 2013, 02:23:52 PM »

Hi all    I have had a slight vibration at 72 mph ? Now it's not that bad . But over the years I have replaced 8 tires , all balanced and put on the balance master rings . I do have an air bag leveling system . When I installed it I measured the height of the coach when it was stock and adjust the air to match while driving. So I don't think it has anything to do with the vibration but who knows ? My tires all show no unusual wear .      Any ideas ? 

thanks    dave
Logged

1990 mci 102c  6v92 ta ht740  kit,living room slide . home base huntsville ontario canada
Dave5Cs
Hero Member
*****
Offline Offline

Posts: 1448


1979 MCI MC5Cs 6V-71 HT-740 Allison, Roseville, CA




Ignore
« Reply #1 on: October 12, 2013, 02:37:09 PM »

Cracked hub, bad bearing or race, bent something on your control arms, cracked U-joint or loose bolts on your drive shaft? That's all I got!...

Dave5Cs
Logged

sledhead
Sr. Member
****
Online Online

Posts: 338





Ignore
« Reply #2 on: October 12, 2013, 02:52:27 PM »

All new air bags ( 8 )
     new shocks  (Cool
     new brake shoes , seals
     
 I grease all the nipples drive shaft , brakes , all the other ones (100rds , 100rds of them ) 

It has had the vibration for years . 

  on the control arms   how do I check them ?   
Logged

1990 mci 102c  6v92 ta ht740  kit,living room slide . home base huntsville ontario canada
wg4t50
Hero Member
*****
Offline Offline

Posts: 758





Ignore
« Reply #3 on: October 12, 2013, 03:58:56 PM »

Found an issue with too low air psi in the tag axle bags, caused the tag to hop. Had the MC7
If you knew the frequency of the vibration, it would be very simple to locate.
Logged

MCI7 20+ Yrs
Foretravel w/ISM500
Dave5Cs
Hero Member
*****
Offline Offline

Posts: 1448


1979 MCI MC5Cs 6V-71 HT-740 Allison, Roseville, CA




Ignore
« Reply #4 on: October 12, 2013, 04:06:35 PM »

Rarely happens but if they are bent you will see it especially if you ran  over something or it was hit etc. I was just throwing some things out there that it might be...You said you greased the U-Joints but did you check the bolts and nuts.

Dave5Cs
Logged

edroelle
Sr. Member
****
Offline Offline

Posts: 351


1998 Royale Prevost




Ignore
« Reply #5 on: October 12, 2013, 04:22:22 PM »

Usually, a vibration is caused by a rotating element.    Bearings can cause it BUT, they are a small diameter and relatively light unless there is significant wear and loosness.   I would first check tire balance and universal joint wear.   A tire with a loose belt can cause a problem.    What brand are you tires?

A resonance in the body can also cause a problem.   You want a sturdy, tight, body.   Are there rivets loose or indications the side walls are bending?

Ed Roelle
Flint, MI
Logged
sledhead
Sr. Member
****
Online Online

Posts: 338





Ignore
« Reply #6 on: October 12, 2013, 04:53:08 PM »

Tires fs400 firestone new and all balanced       dave
Logged

1990 mci 102c  6v92 ta ht740  kit,living room slide . home base huntsville ontario canada
skihor
Sr. Member
****
Offline Offline

Posts: 290





Ignore
« Reply #7 on: October 12, 2013, 06:52:05 PM »

I once ignored a vibration and I found the issue was loose and eventually sheared driveshaft flange bolts. Out of time u joints, worn splines on a 2 piece driveline, worn u joints are all suspect. Also, with my 6V92/5 spd allision conversion, it has a very short driveline. It is VERY critical on ride height. Worn shocks can allow harmonic vibrations to happen. Many suspension components could lead to harmonics.
Don
Logged
Dave5Cs
Hero Member
*****
Offline Offline

Posts: 1448


1979 MCI MC5Cs 6V-71 HT-740 Allison, Roseville, CA




Ignore
« Reply #8 on: October 12, 2013, 08:33:08 PM »

Does it happen all the time, when up at running temp only at 72MPH. Where do you feel it? In the rear, front, all over, Is there a noise with it and where? Is it felt from drivers seat or when foot is on the brake or fuel peddle etc.? Check air pressure in all tires against a weigh stations reading and then a tire chart with the weigh chart to see if you might be running to high or low pressure.

Dave5Cs
Logged

wg4t50
Hero Member
*****
Offline Offline

Posts: 758





Ignore
« Reply #9 on: October 12, 2013, 11:44:57 PM »

Another question, vibration occur when coasting, accelerating, or just cruising ?
Have also had the U Joint issue, vibrate when adding power, smooth when coasting, yup, loose bolts on beating caps.
Why I have enjoyed the bus sperience, never a day of no education  Grin
Logged

MCI7 20+ Yrs
Foretravel w/ISM500
sledhead
Sr. Member
****
Online Online

Posts: 338





Ignore
« Reply #10 on: October 13, 2013, 07:14:10 AM »

Over the years I have tried lot's of things. It is only at 72- 77 mph after that I can't feel it. I thought it had to be a tire problem . But I think it,s time to remove the drive shaft . Would it be wise to put in a new u joint and have it balanced ? if so who, would balance it ? machine shop ? transmission shop ?     

let off on the gas    no change
once I put in neutral and coasted down to a stop  no change 

about the only time I have not felt it is when you first start out when its cold out side . But after driving for say 1/2 hour if I drive at 72-74 mph I can feel it.

now  this spring was the first time ever that my son was driving the coach and I went for a walk in side ( wow was that weird ) I could feel a small bouncing up and down when I was sitting on the toilet ( just sitting ) which is just in front of the drive tires on the driver side .

again this is a very small vibration .

thanks again     dave   
Logged

1990 mci 102c  6v92 ta ht740  kit,living room slide . home base huntsville ontario canada
luvrbus
Hero Member
*****
Online Online

Posts: 12060




Ignore
« Reply #11 on: October 13, 2013, 07:20:52 AM »

Probably just a out of balance or out of round brake drum high speed vibrations can be a PITA to chase down I had one it took me for ever to figure out the the 3 longer studs on 1 wheel was causing the problem.

If you can find a truck shop that spin balances on the rig they can find it if a tire or wheel problem
Logged

Live each day like it was your last,one day it will be
Len Silva
Hero Member
*****
Offline Offline

Posts: 4083


Angle Parked in a Parallel Universe


WWW

Ignore
« Reply #12 on: October 13, 2013, 10:18:12 AM »

What is the frequency of the vibration.  At that speed the wheels are turning at 425-450 rpm and the drive train at 16-1800.  It sounds like something rotating at wheel speed, so if not the tires, it is likely a brake drum.
Did you have them spin balanced on the bus?
Can you get it to a chassis dyno? That might help.
Can you jack up one rear wheel at a time and spin it at that speed? That would tell you front or rear.
Logged


Hand Made Gifts

Ignorance is only bliss to the ignorant.
ol713
Full Member
***
Offline Offline

Posts: 150



WWW

Ignore
« Reply #13 on: October 13, 2013, 03:56:07 PM »


  Hi;
     When you greased the u-joints, did you happen to grab the
     drive shaft and see if it moves up or down??
                                Merle.







All new air bags ( 8 )
     new shocks  (Cool
     new brake shoes , seals
     
 I grease all the nipples drive shaft , brakes , all the other ones (100rds , 100rds of them ) 

It has had the vibration for years . 

  on the control arms   how do I check them ?   
Logged
pvcces
Hero Member
*****
Offline Offline

Posts: 750





Ignore
« Reply #14 on: October 13, 2013, 10:42:43 PM »

We had a pretty good vibration at the same speed as you have. Ted Campbell pulled the parking brake drum and rear axle. Then, he had me spin the drive shaft at the same speed. Most of the vibration was gone. I was shocked at how much that small drum threw the line out of balance.

It might be something to look into, if you still have the drum.

Tom
Logged

Tom Caffrey PD4106-2576
Suncatcher
Ketchikan, Alaska
Pages: [1] 2  All   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.18 | SMF © 2013, Simple Machines Valid XHTML 1.0! Valid CSS!