Annuder Vibration Question

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Nov 2, 2021 | 03:51 PM

rcwarship

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Joined: Aug 2019

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Annuder Vibration Question

Hi All,

I was hoping to get your help with some ideas on Betsy's problems - LOL, everyone names their truck, don't they?

Details - 1986 F150 4.9L manual 5-speed, 2WD. 140,000 miles, Washington state truck - minor surface rust.

It always vibrates at 68+ mph, most of the time while in neutral and coasting to a stop sign while at lower speeds, sometimes while accelerating 20-45 mph.
No vibration through steering wheel
I don't see any shiny spots/broken welds for balance on the drive shafts (twin shafts with slip fit & carrier bearing).

While coasting to a stop, it's vibrating while in neutral & with the clutch not depressed:

With the clutch depressed, it still vibrates
When put in gear (clutch pedal still depressed) - vibration quits
May or may not vibrate on acceleration, mostly not

To date:
Truck jacked up & wheels spun/rocked, they look good. There's no bearing noise, they spin for a while, no undue drag - I don't think that wheel bearings are the issue.

I'm thinking that u-joints & the carrier bearing are the next step - any other ideas?

Thank you in advance,
Jon

Nov 2, 2021 | 04:00 PM

Conanski

FTE Legend

Joined: Jun 2006

Posts: 31,930

Likes: 1,499

From: Ottawa, Ontario

Weak/broken engine mounts perhaps, does the shifter move to the side a lot when you're on the gas vs coasting?