Pulsing vibration at around 55-65 mph - Page 3 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

pkbinplano · 10-30-2010, 02:06 PM

BINGO !!! Bad fan clutch ! It's loose. The warmer the truck gets the more loose it gets. Vibrates at highway speeds when you feather the pedal like going up a hill.

texasbigbear_wink · 10-30-2010, 07:04 PM

Pk your lucky on that one.
Posted via Mobile Device

GMC Guy · 11-09-2010, 10:50 PM

well i just finished replacing my driver side lower control arm. see my thread about that. also replaced the tranny mount, wow was that shot...also noticed that my getto exhaust pipes were loose and might have been clanking around. so i got everything back together and tightened up. went for a trip down the highway, and my vibrations have milded down some. still a slight vibration at 55, but smooth over that. also my speedo needle calmed down and read the mph more accurate, probably cuz the tranny is nice and anchored down now lol
so now i'm going to look into the tires more, unless anyone else has some ideas? i'm open for suggestions lol

GMC Guy · 10-26-2010, 03:56 PM

Quote:

Originally Posted by Cue-Ball

And yes, a 3" drop is more than enough to screw up your pinion angles.

what does everyone when they lower their truck? i haven't heard any mention of needing to adjust pinion angle when they throw a lowering kit on there. although it makes perfect sense as to why it would mess up the driveshaft angle

Cue-Ball · 10-26-2010, 06:19 PM

Lowering a vehicle is not a guarantee of having pinion angle issues. Lots of guys lower all sorts of cars/trucks and have no problems. Other guys lower a few inches and everything is out of whack. You might just be one of the unlucky ones.

GMC Guy · 10-26-2010, 07:07 PM

i'm not really familiar with pinion angle, so could someone let me know how to check/adjust my pinion angle?

texasbigbear_wink · 10-26-2010, 08:16 PM

You have done the same thing as me spent a lot of time checking everything out and by the time you get dun you could have gotten a new set of tires. The first thing I would have did would of Ban like the other guy said and swap tires with somebody. You can not tell a bad tire just by looking at it. If you have covered everything els like you said you did then I would be about 95% sure it's a bad tire but I could be wrong. I just hope you can figure it out before it cost you and arm and a leg.
Posted via Mobile Device

GMC Guy · 10-26-2010, 08:23 PM

Quote:

Originally Posted by texasbigbear_wink

You have dun the same thing as me spent a lot of time checking everything out and by the time you get dun you could have gotten a new set of tires. The first thing I would have did would of Ban like the other guy said and swap tires with somebody. You can not tell a bad tire just by looking at it. If you have covered everything els like you said you did then I would be about 95% sure it's a bad tire but I could be wrong. I just hope you can figure it out before it cost you and arm and a leg.
Posted via Mobile Device

oh believe me, me too... i don't have an arm and a leg to give lol

texasbigbear_wink · 10-26-2010, 08:46 PM

I spent $95 on new u joints and balancing the drive shaft, replaced trans mount, inner and outer wheel bearings, fly wheel, had the tires balanced many times thinking they were not dun right, then one day I had a flat that could not be fixt so I had 4 new tires put on and solved a years worth of trying to figure that dam pulsing vibration out.
Posted via Mobile Device

texasbigbear_wink · 10-27-2010, 08:26 PM

Well first I would get the front on some Jack stands with your truck being low to the ground then remove the nut on the bottom side of the mount first then you can Jack the trans up slowly normally till the stud clears the hole then you will need to remove the two bolts at the top of the mount not sure but I think they are a 15|16 and most of the time you will need a wrench to get to them. I hope that this will help you.
Posted via Mobile Device

GMC Guy · 10-27-2010, 09:25 PM

thanks bigbear, i'm going to get on it tomorrow

datguysaL · 10-27-2010, 11:35 PM

lets us know if it changes anything wen u do that.

GMC Guy · 10-27-2010, 11:45 PM

will do man, gosh i really hope it's something simple....

pkbinplano · 10-28-2010, 06:19 AM

Watching this thread. I have this exact same problem. Feather the gas around 75 mph and get a bad vibration. Going to check mine out this weekend. Had the tranny rebuilt and new carrier bearing and ujoints same time 1200 miles ago. Drive shaft was balanced also. Last time I was under there I noticed the carrier bearing was mounted all the way to one side. Will allign that also.

379redneck · 02-25-2011, 05:46 PM

I had a vibration in the gas pedal at 65. It didnt vibrate the whole truck but it concerned me. If I went faster you could feel it in floor, but that was the worst it got because I didnt want to go faster and realy mess it up. I just happened to check my oil because it leaks, not because of the vibration, and it was very low(below the minimum line). I added oil and the vibration stopped completely. I know it sounds odd and stupid but it was something I never would have thought about and nobody else did either.
Good luck. Hope its nothing major.

Sick5 · 12-15-2012, 07:53 PM

So... did you find out what it was...?
this is all good info for me since im having same issue but mine doesnt go away till the speed drop. And i dont mean letting off the gas. Thats one of the reason why im thinking it may be my tires

GMC Guy · 12-15-2012, 09:32 PM

well i haven't done anything yet to really resolve the issue. since buying a 97 K2500 over a year and a half ago, the old truck has been parked in the garage relieved of daily driving service. it's just waiting for a complete build with a larger budget and more time.

but the problem has to be either a bad tire(s), out of round wheels (they're old aluminum wheels), or the fact that i have wheel spacers on the rear. all of which will be getting replaced with my choice of wheels and tires anyway. total build up, new rubber, new wheels, and the correct backspacing has to make the vibrations go away, right....?

Redline · 06-27-2013, 09:36 PM

Any updates on this issue. I have a 74, k20 350 , 350 trans with same problem. New tires, new ujoints, new drive shaft. Had the back cover off of the rearend no obvious wear patterns. PO did replace 203 with a 205. After replacing extremely loud exhaust with a stock exhaust I noticed it does it also when I press the gas pedal all the way to the floor. It appears the heavy vibration( imbalance) is when the engine is under load. This morning I was in 3 gear and started feeling it at about 55, I down shifted to 2nd and imbalance speed up. This confirms it is not in the tires. Any help is appreciated, even WAG's

Thanks Mike
Posted via Mobile Device

y5mgisi · 06-27-2013, 10:20 PM

Subscribed. I HATE vibrations...

Keith Seymore · 06-28-2013, 08:27 AM

Quote:

Originally Posted by Redline

Any updates on this issue. I have a 74, k20 350 , 350 trans with same problem. New tires, new ujoints, new drive shaft. Had the back cover off of the rearend no obvious wear patterns. PO did replace 203 with a 205. After replacing extremely loud exhaust with a stock exhaust I noticed it does it also when I press the gas pedal all the way to the floor. It appears the heavy vibration( imbalance) is when the engine is under load. This morning I was in 3 gear and started feeling it at about 55, I down shifted to 2nd and imbalance speed up. This confirms it is not in the tires. Any help is appreciated, even WAG's

Thanks Mike
Posted via Mobile Device

Quote:

Originally Posted by y5mgisi

Subscribed. I HATE vibrations...

Please refer to the flow charts at the end of this thread: http://67-72chevytrucks.com/vboard/s...d.php?t=522180

This is the thought process used to fix any vibration.

It's all about separating the potential root causes (so that you know what you don't have to worry about - so you can focus on what you do have to worry about).

K

y5mgisi · 06-28-2013, 07:23 PM

Thanks for that Keith!

Redline · 06-28-2013, 07:34 PM

Thank you for the chart I will start working down the list tomorrow morning. I have been messing with the truck a little today and did confirm if I am in 3 gear running around 45 I can not feel anything as soon as I get over 50 I do. As soon as I drop down in to 2 gear at 45 or and the RPM's are high the vibration is much much worse. Basically anytime the RPMs are over 2500 or I have the throttle wide open is when I feel the vibration.

Mike

Redline · 06-30-2013, 07:49 PM

Replaced harmonic balancer. Not it.....
Posted via Mobile Device

motornut · 07-01-2013, 09:51 AM

I had a blade throw off a burbs block took out the brake lines ,but caused a heck of a vibration
check it for cracks?

wildjoe330 · 07-12-2017, 03:58 PM

Do all of these trucks with the vibration problem have the NP 203 Transfer Case???
All Dodge, Ford, Chevrolet, have these put into them. And I have seen a dodge online
with the same. Does the NP203 have need for a new bearing on the front of the output
Shaft???

10-30-2010, 02:06 PM	#1
pkbinplano pkbinplano Join Date: Nov 2002 Location: Plano Texas Posts: 370	Re: Pulsing vibration at around 55-65 mph BINGO !!! Bad fan clutch ! It's loose. The warmer the truck gets the more loose it gets. Vibrates at highway speeds when you feather the pedal like going up a hill. __________________ http://www.picturetrail.com/gallery/...7496&members=1 84 chevy silverado aka The Bananna Boat

10-30-2010, 07:04 PM	#2
texasbigbear_wink Registered User Join Date: Oct 2009 Location: Texas Ellis county Posts: 134	Re: Pulsing vibration at around 55-65 mph Pk your lucky on that one. Posted via Mobile Device __________________ 87 Chevy R10 LB 02 Nissan Sentra GXE

11-09-2010, 10:50 PM	#3
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	Re: Pulsing vibration at around 55-65 mph well i just finished replacing my driver side lower control arm. see my thread about that. also replaced the tranny mount, wow was that shot...also noticed that my getto exhaust pipes were loose and might have been clanking around. so i got everything back together and tightened up. went for a trip down the highway, and my vibrations have milded down some. still a slight vibration at 55, but smooth over that. also my speedo needle calmed down and read the mph more accurate, probably cuz the tranny is nice and anchored down now lol so now i'm going to look into the tires more, unless anyone else has some ideas? i'm open for suggestions lol __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)]

10-26-2010, 06:19 PM	#5
Cue-Ball Registered User Join Date: Sep 2010 Location: Kirkland, WA Posts: 241	Re: Pulsing vibration at around 55-65 mph Lowering a vehicle is not a guarantee of having pinion angle issues. Lots of guys lower all sorts of cars/trucks and have no problems. Other guys lower a few inches and everything is out of whack. You might just be one of the unlucky ones.

10-26-2010, 07:07 PM	#6
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	Re: Pulsing vibration at around 55-65 mph i'm not really familiar with pinion angle, so could someone let me know how to check/adjust my pinion angle? __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)]

10-26-2010, 08:16 PM	#7
texasbigbear_wink Registered User Join Date: Oct 2009 Location: Texas Ellis county Posts: 134	Re: Pulsing vibration at around 55-65 mph You have done the same thing as me spent a lot of time checking everything out and by the time you get dun you could have gotten a new set of tires. The first thing I would have did would of Ban like the other guy said and swap tires with somebody. You can not tell a bad tire just by looking at it. If you have covered everything els like you said you did then I would be about 95% sure it's a bad tire but I could be wrong. I just hope you can figure it out before it cost you and arm and a leg. Posted via Mobile Device __________________ 87 Chevy R10 LB 02 Nissan Sentra GXE Last edited by texasbigbear_wink; 10-26-2010 at 09:07 PM.

10-26-2010, 08:46 PM	#9
texasbigbear_wink Registered User Join Date: Oct 2009 Location: Texas Ellis county Posts: 134	Re: Pulsing vibration at around 55-65 mph I spent $95 on new u joints and balancing the drive shaft, replaced trans mount, inner and outer wheel bearings, fly wheel, had the tires balanced many times thinking they were not dun right, then one day I had a flat that could not be fixt so I had 4 new tires put on and solved a years worth of trying to figure that dam pulsing vibration out. Posted via Mobile Device __________________ 87 Chevy R10 LB 02 Nissan Sentra GXE Last edited by texasbigbear_wink; 10-26-2010 at 09:06 PM.

10-27-2010, 08:26 PM	#10
texasbigbear_wink Registered User Join Date: Oct 2009 Location: Texas Ellis county Posts: 134	Re: Pulsing vibration at around 55-65 mph Well first I would get the front on some Jack stands with your truck being low to the ground then remove the nut on the bottom side of the mount first then you can Jack the trans up slowly normally till the stud clears the hole then you will need to remove the two bolts at the top of the mount not sure but I think they are a 15\|16 and most of the time you will need a wrench to get to them. I hope that this will help you. Posted via Mobile Device __________________ 87 Chevy R10 LB 02 Nissan Sentra GXE

10-27-2010, 09:25 PM	#11
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	Re: Pulsing vibration at around 55-65 mph thanks bigbear, i'm going to get on it tomorrow __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)]

10-27-2010, 11:35 PM	#12
datguysaL Registered User Join Date: May 2009 Location: Houston, TX Posts: 155	Re: Pulsing vibration at around 55-65 mph lets us know if it changes anything wen u do that.

10-27-2010, 11:45 PM	#13
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	Re: Pulsing vibration at around 55-65 mph will do man, gosh i really hope it's something simple.... __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)]

10-28-2010, 06:19 AM	#14
pkbinplano pkbinplano Join Date: Nov 2002 Location: Plano Texas Posts: 370	Re: Pulsing vibration at around 55-65 mph Watching this thread. I have this exact same problem. Feather the gas around 75 mph and get a bad vibration. Going to check mine out this weekend. Had the tranny rebuilt and new carrier bearing and ujoints same time 1200 miles ago. Drive shaft was balanced also. Last time I was under there I noticed the carrier bearing was mounted all the way to one side. Will allign that also. __________________ http://www.picturetrail.com/gallery/...7496&members=1 84 chevy silverado aka The Bananna Boat

02-25-2011, 05:46 PM	#15
379redneck Registered User Join Date: Sep 2010 Location: Kingston, PA Posts: 394	Re: Pulsing vibration at around 55-65 mph I had a vibration in the gas pedal at 65. It didnt vibrate the whole truck but it concerned me. If I went faster you could feel it in floor, but that was the worst it got because I didnt want to go faster and realy mess it up. I just happened to check my oil because it leaks, not because of the vibration, and it was very low(below the minimum line). I added oil and the vibration stopped completely. I know it sounds odd and stupid but it was something I never would have thought about and nobody else did either. Good luck. Hope its nothing major. __________________ 87 GMC Sierra 2500 4x4 350/TH350/NP203 Flow Tech long tube headers, throttle body spacer, Edelbrock Performer cam, true dual Flowmaster 40s, 6 inch Superlift suspension lift 2000 silverado extended cab stepside 5.3l. Stock for now

12-15-2012, 07:53 PM	#16
Sick5 C10 CLUB Y QUE! Join Date: Mar 2010 Location: Here Posts: 2,770	Re: Pulsing vibration at around 55-65 mph So... did you find out what it was...? this is all good info for me since im having same issue but mine doesnt go away till the speed drop. And i dont mean letting off the gas. Thats one of the reason why im thinking it may be my tires __________________ C/10 CLUB http://67-72chevytrucks.com/vboard/f...play.php?f=148

12-15-2012, 09:32 PM	#17
GMC Guy Registered User Join Date: May 2009 Location: Sparks, NV Posts: 913	Re: Pulsing vibration at around 55-65 mph well i haven't done anything yet to really resolve the issue. since buying a 97 K2500 over a year and a half ago, the old truck has been parked in the garage relieved of daily driving service. it's just waiting for a complete build with a larger budget and more time. but the problem has to be either a bad tire(s), out of round wheels (they're old aluminum wheels), or the fact that i have wheel spacers on the rear. all of which will be getting replaced with my choice of wheels and tires anyway. total build up, new rubber, new wheels, and the correct backspacing has to make the vibrations go away, right....? __________________ Greg 1974 GMC 1/2 Ton SWB Fleetside L33 5.3/4l65e .................__ ............._____l __\__ ..............l_(O)_ l___(O)] Last edited by GMC Guy; 12-15-2012 at 09:54 PM.



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06-27-2013, 09:36 PM	#18
Redline Registered User Join Date: Feb 2009 Location: Dallas Posts: 60	Re: Pulsing vibration at around 55-65 mph Any updates on this issue. I have a 74, k20 350 , 350 trans with same problem. New tires, new ujoints, new drive shaft. Had the back cover off of the rearend no obvious wear patterns. PO did replace 203 with a 205. After replacing extremely loud exhaust with a stock exhaust I noticed it does it also when I press the gas pedal all the way to the floor. It appears the heavy vibration( imbalance) is when the engine is under load. This morning I was in 3 gear and started feeling it at about 55, I down shifted to 2nd and imbalance speed up. This confirms it is not in the tires. Any help is appreciated, even WAG's Thanks Mike Posted via Mobile Device __________________ 1966 GMC V6 351, Plano, TX 1974 Chevy K20 350/350/205

06-27-2013, 10:20 PM	#19
y5mgisi Second Chance Program Join Date: Jun 2006 Location: Portland, OR Posts: 2,642	Re: Pulsing vibration at around 55-65 mph Subscribed. I HATE vibrations... __________________ 90 Chevy Suburban 2500 5.3 swap/th400/np241/14bltSF/10blt. 77 C20 crew cab Silverado. 396/th400. In work.

06-28-2013, 07:23 PM	#21
y5mgisi Second Chance Program Join Date: Jun 2006 Location: Portland, OR Posts: 2,642	Re: Pulsing vibration at around 55-65 mph Thanks for that Keith! __________________ 90 Chevy Suburban 2500 5.3 swap/th400/np241/14bltSF/10blt. 77 C20 crew cab Silverado. 396/th400. In work.

06-28-2013, 07:34 PM	#22
Redline Registered User Join Date: Feb 2009 Location: Dallas Posts: 60	Re: Pulsing vibration at around 55-65 mph Thank you for the chart I will start working down the list tomorrow morning. I have been messing with the truck a little today and did confirm if I am in 3 gear running around 45 I can not feel anything as soon as I get over 50 I do. As soon as I drop down in to 2 gear at 45 or and the RPM's are high the vibration is much much worse. Basically anytime the RPMs are over 2500 or I have the throttle wide open is when I feel the vibration. Mike __________________ 1966 GMC V6 351, Plano, TX 1974 Chevy K20 350/350/205

06-30-2013, 07:49 PM	#23
Redline Registered User Join Date: Feb 2009 Location: Dallas Posts: 60	Re: Pulsing vibration at around 55-65 mph Replaced harmonic balancer. Not it..... Posted via Mobile Device __________________ 1966 GMC V6 351, Plano, TX 1974 Chevy K20 350/350/205

07-01-2013, 09:51 AM	#24
motornut 78K & 79C Jimmys Join Date: Nov 2009 Location: Ottawa Ont CANADA Posts: 7,901	Re: Pulsing vibration at around 55-65 mph I had a blade throw off a burbs block took out the brake lines ,but caused a heck of a vibration check it for cracks? __________________ John 1978 GMCJimmy4X4-350/203 1979 GMCJimmy4X2-305/350

07-12-2017, 03:58 PM	#25
wildjoe330 Registered User Join Date: Jul 2017 Location: A Posts: 1	Re: Pulsing vibration at around 55-65 mph Do all of these trucks with the vibration problem have the NP 203 Transfer Case??? All Dodge, Ford, Chevrolet, have these put into them. And I have seen a dodge online with the same. Does the NP203 have need for a new bearing on the front of the output Shaft???

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