Vibration at 40 to 45 mph

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PeteD

New member
Joined
Jul 15, 2018
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2
I have a 1999 Bounder which is on a Chevy P30 chassis.  I bought it in May and have driven over 3000 miles.  It now has about 45,500 miles on it.  There is a very distinct vibration in the front end when traveling 40 to 45 mph.  Above 50 mph,  smooth as silk.  The coach has a Safe Steer system and new suspension bushings and new front spring air bags inflated to 70psi.  I first suspected an out of balance tire.  When I went to balance the front tires,  I found the left one severly cupped and the right one a little cupped.  I replaced the tires and watched them being balanced at a Les Schwab truck center.  The vibration did not change in any significant way after getting the new tires.
There is no bad play in the steering wheel and the coach does not pull.  With the Safe-Steer in place,  you can't really shake the tie rods,  etc to check the ball joints,  but other than this vibration,  she is a delight to drive.  At this point I suspect the front shocks but not sure why I am only seeing this vibration at these speeds.    Thoughts and advice are welcome.
 

kdbgoat

Well-known member
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Apr 16, 2014
Posts
6,313
I don't know about the vibration, but bad shocks are the most likely cause of your tires cupping. One odd thing that can cause a vibration at certain speeds and no vibration at other speeds are bad u-joints. This can appear to be in the front as well as the back, leading one to believe it's a front end issue.
 
S

sightseers

Guest
check the 2 piece driveshaft for a worn out center carrier bearing.
 

Tom

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Jan 13, 2005
Posts
48,625
Had a similar symptom (vibration in a small speed range) on an SUV. A work colleague who repaired vehicles in his spare time said "it's probably the drivetrain". We took it for a drive, and he confirmed it. Had all the U-joints replaced, and the vibration went away.
 

Gary RV_Wizard

Site Team
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Feb 2, 2005
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At our Silver Springs FL home
Worn shocks can cause cupping, but so can various alignment and front-end wear problems. I know you've had many of those components replaced, but that doesn't mean the net effect of all the various adjustments ends up right.

Severe cupping means the tire is violently bouncing up & down, so typically causes more than just slight vibration.  However, the heaviness of a motorhome can dampen out a lot of that and the driver only experiences a mild effect. 
 

PeteD

New member
Joined
Jul 15, 2018
Posts
2
Thank you all.  I had also suspected the u-joints. I will get under and check them and the carrier.  I'll report the final solution... by and by. 
 
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