cyclic vibration - The 1947 - Present Chevrolet & GMC Truck Message Board Network

sellersrodshop · 04-18-2013, 03:10 AM

i'm finally fixing to tackle some long needed work on my truck. the biggest concern is a "cyclic" vibration at cruising speeds. its weird, as it comes & goes in a consistent pattern & doesn't seem to change noticeably with speed changes. i'm going to check driveline angles tomorrow & see where those are at. I also put new tires on not too long ago but problem was the same with the old yokohama's so ruling out tire balance issues. best way I can describe it is a wet dog shaking. it starts out light, then gets heavier, then back to light & starts over again. any ideas??

Ziegelsteinfaust · 04-18-2013, 12:12 PM

Have you greased your u joints? Or are they old, and possibly going bad.

BR3W CITY · 04-18-2013, 03:04 PM

If you have a 2 piece shaft, I'd say its the carrier bearing. If you pop it in nuetral and the shaking stops, its not the u joint.

When you put new tires on did they have to use a lot of weight on one wheel, possibly indicating that the wheel is out of round.

sellersrodshop · 04-18-2013, 06:59 PM

ok, a little more info: its a shortbed, single driveshaft. u joints feel solid, no play in those. I did some driveline measuring today & some things are off. here's what I found:

truck sits at a 3 degree rake (down in front) its lowered in front w/ 3" drop springs & 2.5" drop spindles (early classic) & 5" drop rear springs (early classic)
engine tranny sits at a 0-1 degree up
rear diff is at 0 degrees

shocks sitting in stock mounts are at 45 degrees. I need to fab new brackets but have known this for a good while.

how it sat with the old tires. rears were 285/50-18 current tires are 295/45-18 so a little shorter.

bodydropped68 · 04-19-2013, 10:23 AM

Check you u joints they may feel ok on the truck but remove the driveshaft and feel them see if they feel notchie or stiff as you move them. mite find a damaged one good luck.

wraprail · 05-03-2013, 09:40 AM

If your diff is 0 degrees and your trans is 0-1 up, I would start by fixing this.
Read this and adjust acordingly.
http://www2.dana.com/pdf/J3311-1-DSSP.pdf
Replace ujoints and that should do it

Mikec10 · 05-07-2013, 10:04 PM

Are your wheels properly balanced? I'd check that first... Amazing how much vibration goes away after you balance a set of tires.

04-18-2013, 03:10 AM	#1
sellersrodshop Registered User Join Date: Jul 2009 Location: Shooting Creek, NC Posts: 52	cyclic vibration i'm finally fixing to tackle some long needed work on my truck. the biggest concern is a "cyclic" vibration at cruising speeds. its weird, as it comes & goes in a consistent pattern & doesn't seem to change noticeably with speed changes. i'm going to check driveline angles tomorrow & see where those are at. I also put new tires on not too long ago but problem was the same with the old yokohama's so ruling out tire balance issues. best way I can describe it is a wet dog shaking. it starts out light, then gets heavier, then back to light & starts over again. any ideas?? __________________ I called my stockbroker last week and asked him what I should be buying .......... he said "Canned Goods and Ammunition".

04-18-2013, 12:12 PM	#2
Ziegelsteinfaust Registered User Join Date: Dec 2012 Location: Temple City Posts: 3,558	Re: cyclic vibration Have you greased your u joints? Or are they old, and possibly going bad.

04-18-2013, 03:04 PM	#3
BR3W CITY meowMEOWmeowMEOW Join Date: Sep 2009 Location: MKE WI Posts: 7,128	Re: cyclic vibration If you have a 2 piece shaft, I'd say its the carrier bearing. If you pop it in nuetral and the shaking stops, its not the u joint. When you put new tires on did they have to use a lot of weight on one wheel, possibly indicating that the wheel is out of round. __________________ *'66 Short Step / SD Tuned / Big Cam LQ4 / Backhalfed /Built 4l80e / #REBUILDEVERYTHING* MY BUILD THE H8RDCPTR //\\ MY YOUTUBE CHANNEL REV J HD

04-18-2013, 06:59 PM	#4
sellersrodshop Registered User Join Date: Jul 2009 Location: Shooting Creek, NC Posts: 52	Re: cyclic vibration ok, a little more info: its a shortbed, single driveshaft. u joints feel solid, no play in those. I did some driveline measuring today & some things are off. here's what I found: truck sits at a 3 degree rake (down in front) its lowered in front w/ 3" drop springs & 2.5" drop spindles (early classic) & 5" drop rear springs (early classic) engine tranny sits at a 0-1 degree up rear diff is at 0 degrees shocks sitting in stock mounts are at 45 degrees. I need to fab new brackets but have known this for a good while. how it sat with the old tires. rears were 285/50-18 current tires are 295/45-18 so a little shorter. __________________ I called my stockbroker last week and asked him what I should be buying .......... he said "Canned Goods and Ammunition".

04-19-2013, 10:23 AM	#5
bodydropped68 Registered User Join Date: Jun 2006 Location: Tucson, Az Posts: 705	Re: cyclic vibration Check you u joints they may feel ok on the truck but remove the driveshaft and feel them see if they feel notchie or stiff as you move them. mite find a damaged one good luck.

05-03-2013, 09:40 AM	#6
wraprail Registered User Join Date: Sep 2010 Location: Lake Havasu City Arizona Posts: 863	Re: cyclic vibration If your diff is 0 degrees and your trans is 0-1 up, I would start by fixing this. Read this and adjust acordingly. http://www2.dana.com/pdf/J3311-1-DSSP.pdf Replace ujoints and that should do it __________________

05-07-2013, 10:04 PM	#7
Mikec10 Registered User Join Date: Apr 2011 Location: Cleveland, Ohio Posts: 293	Re: cyclic vibration Are your wheels properly balanced? I'd check that first... Amazing how much vibration goes away after you balance a set of tires. __________________ 1980 C10 SWB Yukon 5.3/5 speed 3.73 gears.



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