Vibration when accelerating from stop

RF_Burns

RF_Burns

Super Moderator
Staff member
Sep 7, 2008
5,171
1,369
113
Ontario Canada
Hi All,
When I accelerate from a stop, I feel a definite vibration for the first few seconds. I can't tell if it disappears right when it shifts to second
because that shift is so subtle. I feel it more through the seat than through the steering wheel.

Its not an irregular vibration, but a smooth vibration that fades out. Coming back from the GMCMI rally I was in some crawling stop and go traffic.
It only seemed to occur if I came to a stop.

Any ideas? First gear clutch slipping?

Thanks,
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
Ooh. That's a scary diagnosis. Go to a parking lot and try taking off from stop with wheel cut one way and the other. Get under and check 3 support
bolts on ling shaft bracket. Check for missing inner cap screws by joinys to hubs.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
Joints. And of course recheck Dexron level. If marginal try adding a pint as a test.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
And check the half-shaft bolts. If they are loose, replace them.

Rick "easy stuff first" Denney

On Sun, Sep 24, 2017 at 10:18 AM John R. Lebetski
wrote:

> Joints. And of course recheck Dexron level. If marginal try adding a pint
> as a test.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Rick Denney
73 x-Glacier 230 "Jaws"
Off-list email to rick at rickdenney dot com
 
Rev it up at idle, does it still do it. The Eleganza I picked up started “shuddering” it felt like on my transport trip back. Seems to be the exhaust resonating in my case, thankfully.

I have tons of other stuff to fix on this one if I am to use it!

_____________________________
From: Bruce Hislop
Sent: Sunday, September 24, 2017 9:57 AM
Subject: [GMCnet] Vibration when accelerating from stop
To:

Hi All,
When I accelerate from a stop, I feel a definite vibration for the first few seconds. I can't tell if it disappears right when it shifts to second
because that shift is so subtle. I feel it more through the seat than through the steering wheel.

Its not an irregular vibration, but a smooth vibration that fades out. Coming back from the GMCMI rally I was in some crawling stop and go traffic.
It only seemed to occur if I came to a stop.

Any ideas? First gear clutch slipping?

Thanks,
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Check the bolts on your front hubs, the 4 that go in from the back side into the bearing assembly on the one ton. You can get to them without even
jacking the coach up. You may have to move the wheels back and fourth to get to them all. Loose bolts here will cause just what you're describing.
Hal
--
1977 Royale 101348,

1977 Royale 101586, Diesel powered,

1975 Eleganza II, 101230,

1974 Eagle Bus 45',w/slideout,

Rio Rancho, NM
 
I have beads in the wheels and that vibration occurs once I'm rolling at about 35-40mph and is gone in short order. This starts the moment I press on
the gas. Its a fast vibration, so it maybe engine related. Its a smooth vibration, not sharp. It disappears once I get rolling and the engine RPM is
above 2000.

My engine always seems to run rough when I rev the engine from idle, so it maybe related to that.

To try to cure that I have changed the coil and pickup to be sure I have proper phased ones (from DickP), new distributor cap, new rotor, new module,
2 sets of spark plugs (AC #7 and now NKG), 2 sets of DickP's plug wires (I pulled the spark plug connector off the wire on a couple trying to remove
the wire from the plug)

One time I tried shorting out each plug in turn by removing the plug wires from the cap and looping a small copper wire around the terminal, then
replacing the wires on the cap. I was able to cut the spark to each cylinder, but I was not able to determine that any one cylinder was the cause,
they were all firing. I gave up thinking it was just the nature of the beast

We are taking it to the family cottage about 30 miles away today, so I'll try to pay more attention to symptoms.
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
If you suspect a light part throttle transitional engine miss, have someone do very light "brake torque" moves from idle to light part throttle in D
in the suspect range. You listen and feel with your hand at tailpipe for miss. Simple quick test to isolate if engine miss or drive train harmonic
vibration. Could be gummed pullover slots in Qjet or any number of things like plug gap wrong. If no miss, move your diagnostic efforts to rotating
drive train assembly parts.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
Seems like there was a discussion on a similar situation a few months ago. If memory serves, I think the problem was the u-joint in the half shaft.
Good luck.
--
Scott Nutter
1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final drive, Quad bags, tankless water heater, everything Lenzi.
Houston, Texas
 
Bruce, check the inboard cv on the drivers side of the coach. The 12 point
bolts thar secure the joint to the final drive flange are know to loosen
and cause the exact symptoms you describe. If they are loose, remove them,
wire wheel the threads, de-grease the internal threads with brake-kleen or
similar, and use blue loctite and retorque them to 55 foot pounds torque.
While you are under there, check your boots for tears. Check the half shaft
carrier bearing on the passenger side as well.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

> Seems like there was a discussion on a similar situation a few months ago.
> If memory serves, I think the problem was the u-joint in the half shaft.
> Good luck.
> --
> Scott Nutter
> 1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final
> drive, Quad bags, tankless water heater, everything Lenzi.
> Houston, Texas
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
So I payed extra attention to the "smooth vibration" I felt while accelerating from stop and it didn't do it this weekend! it was only about 100kms so
not a long trip and all highway.

Today I decided to go into town and dump the black tank. I wasn't thinking about the vibration and then I felt it! So after a few in-town stop
lights and some testing, it appears it happens when the engine is about 1800rpm. Doesn't matter if I'm accelerating or steady state or decelerating,
or any particular speed, at around 1800 RPM there is a vibration. So either an engine in-balance or a resonance at that RPM. May also be related to
the rough engine I feel if I rev the engine.
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
Could the balancer have spun or shifted on rubber? Common Olds issue with age. When it happens try in neutral to rev above and below to rule out
drivetrain.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
Do you also get that vibration when parked but with throttle at 1800 rpm's?
I don't think it's the engine.
--
Scott Nutter
1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final drive, Quad bags, tankless water heater, everything Lenzi.
Houston, Texas
 
I had a problem like that on my Park Avenue. Turned out to be a tire
tread delaminating from the tire casing. The tread was slipping on the
casing. You would think that would be very visible but it was not. It only
happened while accelerating from a stop or very slow speed. After about
25MPH the systems went away. It finally got bad enough that I saw the line
between the cap and casing. I had done a brake job hoping that would help.
It did not. Then I changed the rotors, still no help.

> Do you also get that vibration when parked but with throttle at 1800 rpm's?
> I don't think it's the engine.
> --
> Scott Nutter
> 1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final
> drive, Quad bags, tankless water heater, everything Lenzi.
> Houston, Texas
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--

*John Phillips*
 
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