vibrations with rpm. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

mtdave2 · 11-05-2009, 04:17 PM

I have an off rithmic vibration at 2700 – 3200 rpm, but only while driving at over 50 mph or so.

Vibration goes away, when shifting to higher gear, but keeping mph the same, so I don’t THINK its drive line. It would be connected to mph if it where, and this is rpm

Will not do the vibration while in park/neutral in drive way when reving to the rpms. the motor does sort of vibrate, a differ ant constant type, at around 3k rpm though

Stated after I had the trany rebuilt. Trany man has no ideas. Drive line guys as well.

hum

cdowns · 11-05-2009, 05:19 PM

was the driveshaft taken apart to put nu ujoint in if so maybe you're out of phase

piecesparts · 11-05-2009, 05:28 PM

Is the driveshaft the right length? If you have done some work onthe shaft or changed out the tranny, then there is a chance that the length is a little too short for the spline on the tranny and you have a vibration.

BB72CHEVKT · 11-05-2009, 05:35 PM

Could it have something to with the gear vendors install?

dwcsr · 11-05-2009, 06:17 PM

Possibly the Converter or the clutch fan. Make sure they didn't crack the cap when installing the trans.

SCOTTMO · 11-05-2009, 06:25 PM

Check to see that the trans is not grounding out on the crossmember also
you might want to remove the drive shaft and rotate it 180 deg.

unclewatts · 11-05-2009, 10:56 PM

This kind of problem is very difficult to solve because it can be any number of things. One good way of diagnosing it is to have someone in the cab run the gas pedal while you go over everything with a stethoscope.

Pont406 · 11-05-2009, 11:06 PM

My truck had a vibration at 50 mph and up. I also thought that it was motor or trans. My buddy ran it on the chasis dyno and it didn't vibrate at all. I rebuilt front end and install new tires. All vibration is gone. Do you have a chasis dyno in your area? I don't know what's a rate there but here it's around $80-90 for 3 pulls. AT the same time you will know if your air/fuel ratio and a lot of other stuff is right. Might help to figure out your power loss also.

Sammy · 11-05-2009, 11:18 PM

Torque converter bolts, tranny mount could be any of these. The out of phase D/S is also another good suggestion even a dry U joint.

mtdave2 · 11-06-2009, 02:03 AM

good info thanks...

more info for you..

i installed the gearvendor, and had the drive line done and redone, see other post! .. no vibrations, all was well.

there were stickers put on the drive lines to mark where they go together, so that isnt the prob, though ilike the idea of rotating it 180, ill try that.

had the trany rebuilt, that is when the vibration started. so my number one thought is the converter. though, i would think id have the same prob in park.

mtdave2 · 11-06-2009, 02:05 AM

clutch fan? you mean the one on the front of the motor?

petey-pablo · 11-06-2009, 04:48 AM

This could also be that the front tires have uneven wear cause by hard braking. Have you smashed on your brakes lately, You could ruien a new set of tires by slamming on the brakes or a hard stop enough to cause the skid this causes the vehicle to viberate at a certain speed and if you speed up or decelerate it goes away..

mtdave2 · 11-06-2009, 11:06 AM

if it were tires then i shouldnt go away just by shifting into over drive..

and they are nice shiney new tires too =)

tim21391 · 11-06-2009, 11:16 AM

a friends driveshaft didnt look to be bent but when he took it somewhere it was off my like.002 or .02 i cant remember but it wasnt visable to the naked eye and it kept vibrating the rear seal out of the tranny... just my two cents..

mtdave2 · 11-06-2009, 11:24 AM

i did a 180 on the drive line, see what happens. doesn’t make sense to me though. the key here is the vibration is with RPM not MPH. when put into neutral it goes away immediately.

mrh33916 · 11-06-2009, 11:38 AM

Did you check the bolts holding the transmission bellhousing to the motor?

mtdave2 · 11-06-2009, 12:53 PM

Quote:

Originally Posted by mrh33916

Did you check the bolts holding the transmission bellhousing to the motor?

no i have not.. never even crossed my mind, but i will.. thanks

Tkmadone · 11-06-2009, 02:29 PM

I have the exact same issue. I removed the clutch fan, the engine mounts, and had the drive shaft redone with no improvement. I'm going to replace the tranny mount next.

RustyParts · 11-07-2009, 06:23 AM

I would remove the bolts from the torque convertor and rotate the convertor on the flywheel one bolt hole and see if the vibration changes.

CCCC · 11-07-2009, 01:36 PM

Some very good suggestions from these guys, and if you do as RustyParts suggests (good idea), be certain to check the flex plate for tightness and especially for cracks/incipient breakage. This can cause the type of vibration you are chasing.

mtdave2 · 11-08-2009, 04:31 PM

i took the camper on a short drive, and i did some more tests.

same vibration at the same rpms, shift in od, and its gone. finally have enough clear highway to get the rpm back up in od.. has the vibration too.

also, i put in neutral at the top end of the rpm vibration, of course they stopped when it went to an idle. then i revved it up to the vibration range, and i did get some vibration, though not as pronounced.

it is defiantly forward of the gearvendor.. so trany, converter, flex plate, or something in or on the engine.

would a cam retarded a tooth or a slightly flatted cam lobe cause this?

ill get a new clutch fan and put it on while im taking the timing chain cover off to have a peak.

k5hart · 11-08-2009, 04:59 PM

I had a problem similar to that when my driveshaft was too long. It was pushed all the way in to the tailshaft which was putting it somewhat in a bind.

cduster · 11-08-2009, 05:35 PM

Harmonic balancer? Just a thought

11-05-2009, 04:17 PM	#1
mtdave2 newly minted old timer Join Date: Dec 1999 Location: Hudson WI Posts: 3,521	vibrations with rpm. I have an off rithmic vibration at 2700 – 3200 rpm, but only while driving at over 50 mph or so. Vibration goes away, when shifting to higher gear, but keeping mph the same, so I don’t THINK its drive line. It would be connected to mph if it where, and this is rpm Will not do the vibration while in park/neutral in drive way when reving to the rpms. the motor does sort of vibrate, a differ ant constant type, at around 3k rpm though Stated after I had the trany rebuilt. Trany man has no ideas. Drive line guys as well. hum __________________ ____________________________________________ 72 c20 longhorn 65k org miles and counting! 69 k10 Suburban

11-05-2009, 05:19 PM	#2
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: vibrations with rpm. was the driveshaft taken apart to put nu ujoint in if so maybe you're out of phase __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

11-05-2009, 05:28 PM	#3
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: vibrations with rpm. Is the driveshaft the right length? If you have done some work onthe shaft or changed out the tranny, then there is a chance that the length is a little too short for the spline on the tranny and you have a vibration. __________________ Frank

11-05-2009, 05:35 PM	#4
BB72CHEVKT Junior Member Join Date: Mar 2007 Location: Hideaway, TX Posts: 4,950	Re: vibrations with rpm. Could it have something to with the gear vendors install? __________________ 71 Suburban 350/700R4 Project Trixie 72 CHEVY,Highlander,SWB,396,T400

11-05-2009, 06:17 PM	#5
dwcsr Hollister Road Co. Join Date: Apr 2005 Location: Houston Posts: 6,134	Re: vibrations with rpm. Possibly the Converter or the clutch fan. Make sure they didn't crack the cap when installing the trans.

11-05-2009, 06:25 PM	#6
SCOTTMO powdercoater Join Date: Dec 2008 Location: mesa,az Posts: 203	Re: vibrations with rpm. Check to see that the trans is not grounding out on the crossmember also you might want to remove the drive shaft and rotate it 180 deg. __________________ SCOTT

11-05-2009, 10:56 PM	#7
unclewatts 70 Chevrolet=Obsession Join Date: Jun 2009 Location: nice ca Posts: 1,067	Re: vibrations with rpm. This kind of problem is very difficult to solve because it can be any number of things. One good way of diagnosing it is to have someone in the cab run the gas pedal while you go over everything with a stethoscope. __________________ I'm Just like my truck. Old, Ugly and Grouchy. Except my truck starts easily in the morning and doesn't smoke! IT'S NOT EASY BEING GREEN! -Kermit the frog 1970 Chevrolet C-10 Longbed Stepside : 350, Muncie M20, 3.08 GM corp. positraction Forest green exterior/light green interior(Where all my money goes) 1996 Toyota Corolla (Parts runner)

11-05-2009, 11:06 PM	#8
Pont406 Registered User Join Date: Aug 2007 Location: West Hills, California Posts: 679	Re: vibrations with rpm. My truck had a vibration at 50 mph and up. I also thought that it was motor or trans. My buddy ran it on the chasis dyno and it didn't vibrate at all. I rebuilt front end and install new tires. All vibration is gone. Do you have a chasis dyno in your area? I don't know what's a rate there but here it's around $80-90 for 3 pulls. AT the same time you will know if your air/fuel ratio and a lot of other stuff is right. Might help to figure out your power loss also.

11-05-2009, 11:18 PM	#9
Sammy Registered User Join Date: Apr 2000 Location: Bonne Terre, Mo Posts: 3,005	Re: vibrations with rpm. Torque converter bolts, tranny mount could be any of these. The out of phase D/S is also another good suggestion even a dry U joint. __________________ '69 Chevy Long Fleet & '71 GMC Short Step & Project "ODD BALL" "You can wash a pig, soak it in most expensive perfume. In the end it is still just a pig." ODD BALL build thread http://67-72chevytrucks.com/vboard/s...d.php?t=478629"

11-06-2009, 02:03 AM	#10
mtdave2 newly minted old timer Join Date: Dec 1999 Location: Hudson WI Posts: 3,521	Re: vibrations with rpm. good info thanks... more info for you.. i installed the gearvendor, and had the drive line done and redone, see other post! .. no vibrations, all was well. there were stickers put on the drive lines to mark where they go together, so that isnt the prob, though ilike the idea of rotating it 180, ill try that. had the trany rebuilt, that is when the vibration started. so my number one thought is the converter. though, i would think id have the same prob in park. __________________ ____________________________________________ 72 c20 longhorn 65k org miles and counting! 69 k10 Suburban

11-06-2009, 02:05 AM	#11
mtdave2 newly minted old timer Join Date: Dec 1999 Location: Hudson WI Posts: 3,521	Re: vibrations with rpm. clutch fan? you mean the one on the front of the motor? __________________ ____________________________________________ 72 c20 longhorn 65k org miles and counting! 69 k10 Suburban

11-06-2009, 04:48 AM	#12
petey-pablo "THE GREEN GOBLIN" Join Date: Mar 2008 Location: Fremont Ca. Posts: 1,025	Re: vibrations with rpm. This could also be that the front tires have uneven wear cause by hard braking. Have you smashed on your brakes lately, You could ruien a new set of tires by slamming on the brakes or a hard stop enough to cause the skid this causes the vehicle to viberate at a certain speed and if you speed up or decelerate it goes away.. __________________ Petey-pablo "THE GREEN GOBLIN" 1972 Cheyenne 10 Short Fleet Side Front 2.5inch Spindles with 2inch Springs Rear 4inch drop Springs. 454BBC TH400,Posi 1971 Cheyenne 10 Long Fleet Side 454BBC TH350,Posi Sold Drive it like you stole it! Petey-pablo@sbcglobal.net

11-06-2009, 11:06 AM	#13
mtdave2 newly minted old timer Join Date: Dec 1999 Location: Hudson WI Posts: 3,521	Re: vibrations with rpm. if it were tires then i shouldnt go away just by shifting into over drive.. and they are nice shiney new tires too =) __________________ ____________________________________________ 72 c20 longhorn 65k org miles and counting! 69 k10 Suburban

11-06-2009, 11:16 AM	#14
tim21391 Registered User Join Date: Jul 2007 Location: Salina, Kansas Posts: 1,998	Re: vibrations with rpm. a friends driveshaft didnt look to be bent but when he took it somewhere it was off my like.002 or .02 i cant remember but it wasnt visable to the naked eye and it kept vibrating the rear seal out of the tranny... just my two cents.. __________________ 1972 C-10...402/400..flowmaster 40 series 1967 Mustang 347 stroker/C-4 1966 Mustang 289/3-speed 2013 Mustang V6/6speed w/300 ponies I may be 23, but i sure do knows 67-72s are sexy! Its not MPG its smiles per gallon! build started 11/25/08 build thread: http://67-72chevytrucks.com/vboard/s....php?p=2993796

11-06-2009, 11:24 AM	#15
mtdave2 newly minted old timer Join Date: Dec 1999 Location: Hudson WI Posts: 3,521	Re: vibrations with rpm. i did a 180 on the drive line, see what happens. doesn’t make sense to me though. the key here is the vibration is with RPM not MPH. when put into neutral it goes away immediately. __________________ ____________________________________________ 72 c20 longhorn 65k org miles and counting! 69 k10 Suburban



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11-06-2009, 11:38 AM	#16
mrh33916 Project '67 454 Join Date: Jan 2009 Location: Columbia SC Posts: 283	Re: vibrations with rpm. Did you check the bolts holding the transmission bellhousing to the motor?

11-06-2009, 02:29 PM	#18
Tkmadone Registered User Join Date: Aug 2009 Location: Simi Valley, CA Posts: 193	Re: vibrations with rpm. I have the exact same issue. I removed the clutch fan, the engine mounts, and had the drive shaft redone with no improvement. I'm going to replace the tranny mount next.

11-07-2009, 06:23 AM	#19
RustyParts Registered User Join Date: May 2006 Location: Wyman, Kentucky Posts: 403	Re: vibrations with rpm. I would remove the bolts from the torque convertor and rotate the convertor on the flywheel one bolt hole and see if the vibration changes. __________________ 1972 GMC Jimmy, 4WD, 454 CI, 350 Turbo, 4" lift, 35" tires The math teacher said my son "Bubba" could be a mathmatical genius. cause he's got 13 fingers!

11-07-2009, 01:36 PM	#20
CCCC Registered User Join Date: Mar 2007 Location: San Pedro River, SE Arizona Posts: 734	Re: vibrations with rpm. Some very good suggestions from these guys, and if you do as RustyParts suggests (good idea), be certain to check the flex plate for tightness and especially for cracks/incipient breakage. This can cause the type of vibration you are chasing. __________________ CCCC 67 Sting Ray Coupe 327 4sp; 68 K10 Suburban 327 4sp; 69 K20 Lifted 383 4sp; 69 C80 Fire Truck 478 V6 5sp/2sp; 69 C20 Longhorn 327 4sp; 70 C30 Wrecker 350 4sp; 70 C30 Flat Bed 350 4sp; 71 C20 LWB 350 4sp; 72 K5 Blazer 350 4sp; 72 C30 Flat Bed Gooseneck Hauler with sleeper 350/TH400; 72 C20 Longhorn 402 4sp; 52 Mack LTL Supercharged Cummins 5sp x 3sp; 01 Dodge 5.9 HO Cummins 6spd; 02 Safari Trek 2430 8.1 Vortec on Workhorse Chassis; 03 Silverado 2500 HD 4wd Duramax/Allison Moved but still in the family 70 C20 Custom Camper 350/TH350; 72 K5 Blazer CST Highlander 350/TH350 Recently sent to new homes 72 C30 MoHome 402 4sp; 72 K5 Blazer Conv 350 4sp; 75 GMC 6000 Aerial 350 w Allison; 72 GMC 3500 Utility 350 4sp; 70 GMC 3500, 350 4sp

11-08-2009, 04:31 PM	#21
mtdave2 newly minted old timer Join Date: Dec 1999 Location: Hudson WI Posts: 3,521	Re: vibrations with rpm. i took the camper on a short drive, and i did some more tests. same vibration at the same rpms, shift in od, and its gone. finally have enough clear highway to get the rpm back up in od.. has the vibration too. also, i put in neutral at the top end of the rpm vibration, of course they stopped when it went to an idle. then i revved it up to the vibration range, and i did get some vibration, though not as pronounced. it is defiantly forward of the gearvendor.. so trany, converter, flex plate, or something in or on the engine. would a cam retarded a tooth or a slightly flatted cam lobe cause this? ill get a new clutch fan and put it on while im taking the timing chain cover off to have a peak. __________________ ____________________________________________ 72 c20 longhorn 65k org miles and counting! 69 k10 Suburban Last edited by mtdave2; 11-08-2009 at 04:32 PM.

11-08-2009, 04:59 PM	#22
k5hart Registered User Join Date: Nov 2002 Location: Charleston, South Carolina Posts: 1,370	Re: vibrations with rpm. I had a problem similar to that when my driveshaft was too long. It was pushed all the way in to the tailshaft which was putting it somewhat in a bind. __________________ 2006 Silverado CCSB, 1939 Ford Sedan, 1962 BelAir Wagon, 1976 Vega Panel Charleston, South Carolina

11-08-2009, 05:35 PM	#23
cduster Registered User Join Date: Oct 2002 Location: S.W. Michigan Posts: 403	Re: vibrations with rpm. Harmonic balancer? Just a thought __________________ Good Judgment comes from experience. Most experience comes from bad judgment.

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