Need help with vibration - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Orence1 · 09-21-2003, 11:23 PM

Just got the 72 Cheyenne LWB on the road. New BB with a built TH-350. I am getting a nasty vibration/shimmy that I did not have with the old small block set-up. Slightly noticeable at 35mph but as I get up to 60 it gets real obvious. My first thought was a bad tire. Had the fronts checked yesterday and they were OK. Backs are brand new. It feels like a tire going bad. I have had that happen on other cars I have owned. I am wondering what else it could be if it is not the tires. Any suggestions appreciated. Thanks in advance.
Larry

mcmlxix · 09-21-2003, 11:35 PM

Any driveshaft mods?
Center Support Bearing?
U-Joints New/ or realy old?
Were new rear tires High Speed balance?
* Did the weights fall off?
... thats all I can think of for now ...

gashog · 09-21-2003, 11:36 PM

I've had driveshafts and u- joints cause that type of viberation, also check center carrier bearing if still using a one piece driveshaft. Good luck

Scrub · 09-22-2003, 12:16 AM

Does braking have any noticable affect? You may have a bad brake drum. If they get hot and you park the rig with the p-brake on, they can get warped and oblong. It will drive you nuts. Try jacking up one rear wheel at a time to see what happens on each side.

Good Luck

**Richard** · 09-22-2003, 01:03 AM

If you pulled the driveshaft make sure the U-Joints are in phase.

Mechanic · 09-22-2003, 01:50 AM

Check your brand new rear tires and lug nut torque. My "brand new" rear tires almost came off on the way home from vacation a week or so ago. Good luck.

beautimus · 09-22-2003, 04:29 AM

a couple of things come to mind.
1. did you use an internal balance flexplate?
(if you used a small block one it is probably not right.)

2. could be a worn a-arm bushing in the front end.

3. could be a bad tire.

4. it could be a warped rim.

5. uh, thats all i can think of to check. lol
hope that helps,
tony

Professor · 09-22-2003, 11:49 AM

You don't say what your new engine is. Is your new big block an externally balanced engine? If so, did you use the harmonic balancer and flexplate off an internally balanced engine?

oldsub86 · 09-22-2003, 12:02 PM

Who did the transmission? I chased a vibration in my 86 Suburban and changed a whole lot of stuff including tires, drive shaft, universal joints, rear end parts, and engine and transmission mounts, on the advice of pro mechanics - did not help at all really until I had the transmission rebuilt.

If it was not there before, check the new parts you have put in first - your new engine and new transmission would be the primary suspects.

**oldiron** · 09-22-2003, 02:24 PM

Is the vibration coming thru the steering wheel or the seat? Did you remove the idler arm when installing the engine if left loose it also will cause a vibration.
Securely (sp?) jack up the rear end and put the transmission into drive and run upto 35 mph and see if you get the vibration. If you do the check out the drive train and rear wheels. If not you might have a problem in the front end.

Orence1 · 09-23-2003, 10:24 PM

Put the rear wheels up on jackstands tonight, ran it up to 2500 RPM which has really caused vibration and there was nothing. I am assuming that it is not the driveshaft and I need to take a harder look at tires and suspension. Thanks to all of you who shot off some excellent suggestions.
Larry

09-21-2003, 11:23 PM	#1
Orence1 Registered User Join Date: Jan 2000 Location: Bothell, WA Posts: 548	Need help with vibration Just got the 72 Cheyenne LWB on the road. New BB with a built TH-350. I am getting a nasty vibration/shimmy that I did not have with the old small block set-up. Slightly noticeable at 35mph but as I get up to 60 it gets real obvious. My first thought was a bad tire. Had the fronts checked yesterday and they were OK. Backs are brand new. It feels like a tire going bad. I have had that happen on other cars I have owned. I am wondering what else it could be if it is not the tires. Any suggestions appreciated. Thanks in advance. Larry

09-21-2003, 11:35 PM	#2
mcmlxix Collector of Projects Join Date: Apr 2003 Location: Las Vegas Posts: 3,106	Any driveshaft mods? Center Support Bearing? U-Joints New/ or realy old? Were new rear tires High Speed balance? * Did the weights fall off? ... thats all I can think of for now ... __________________ Rich 1972 K5 Blazer CST Click HERE D60 BIG BRAKE UPGRADE Click HERE

09-21-2003, 11:36 PM	#3
gashog Active Member Join Date: Oct 2002 Location: Lake co. california Posts: 192	I've had driveshafts and u- joints cause that type of viberation, also check center carrier bearing if still using a one piece driveshaft. Good luck __________________ 69 Custom/10 454 Turbo 400 and 70 Custom/20 350 Turbo 350, 73 cheyanne C/10 also 69 camaro Z/28 and 85 Iroc Z

09-22-2003, 12:16 AM	#4
Scrub Collector of rusty Items Join Date: Dec 2001 Location: Sisters,Oregon USA Posts: 731	Does braking have any noticable affect? You may have a bad brake drum. If they get hot and you park the rig with the p-brake on, they can get warped and oblong. It will drive you nuts. Try jacking up one rear wheel at a time to see what happens on each side. Good Luck __________________ Scrub Sisters, Oregon - Home of the Sisters Rodeo. 70 GMC 1,000,000 + miles 72 K-20 project, 456 Dana60 front, Corp14 rear w/locker, 265R19.5 tires 20-ply. Warn 12k winches both ends, Cross-over steering with raised tie-rod, Powerbox steering, 4500 watt 120-AC power, Air, Hydraulic aux power, 4 inch lift, 5000 lb air-bags both ends.

09-22-2003, 01:03 AM	#5
Richard Senior Member Join Date: Dec 1999 Location: Southern California Posts: 2,990	If you pulled the driveshaft make sure the U-Joints are in phase. __________________ Richard 1972 K10 Custom Deluxe SWB Fleetside My build https://67-72chevytrucks.com/vboard/...d.php?t=800746

09-22-2003, 01:50 AM	#6
Mechanic Registered User Join Date: Jun 2003 Location: Seattle Posts: 77	Check your brand new rear tires and lug nut torque. My "brand new" rear tires almost came off on the way home from vacation a week or so ago. Good luck. __________________ Shop Labor $75, if you watch $100, if you help $125, Wisecracks-$25, Boxjobs-don't even think about it. Yes,Cash.

09-22-2003, 04:29 AM	#7
beautimus Registered User Join Date: Mar 2002 Location: woodstock, alabama, usa Posts: 938	a couple of things come to mind. 1. did you use an internal balance flexplate? (if you used a small block one it is probably not right.) 2. could be a worn a-arm bushing in the front end. 3. could be a bad tire. 4. it could be a warped rim. 5. uh, thats all i can think of to check. lol hope that helps, tony __________________ i survived cancer and kidney stones, but my kids are killing me.

09-22-2003, 11:49 AM	#8
Professor Registered User Join Date: Mar 2001 Location: Fayetteville, Arkansas Posts: 160	You don't say what your new engine is. Is your new big block an externally balanced engine? If so, did you use the harmonic balancer and flexplate off an internally balanced engine?

09-22-2003, 12:02 PM	#9
oldsub86 Registered User Join Date: Dec 2002 Location: Canada Posts: 695	Who did the transmission? I chased a vibration in my 86 Suburban and changed a whole lot of stuff including tires, drive shaft, universal joints, rear end parts, and engine and transmission mounts, on the advice of pro mechanics - did not help at all really until I had the transmission rebuilt. If it was not there before, check the new parts you have put in first - your new engine and new transmission would be the primary suspects. __________________ 1968 Chevy - 292 with a powerglide

09-22-2003, 02:24 PM	#10
oldiron Designated Grumpy Old Man Join Date: Oct 2001 Location: arlington, washington usa Posts: 3,094	Is the vibration coming thru the steering wheel or the seat? Did you remove the idler arm when installing the engine if left loose it also will cause a vibration. Securely (sp?) jack up the rear end and put the transmission into drive and run upto 35 mph and see if you get the vibration. If you do the check out the drive train and rear wheels. If not you might have a problem in the front end. __________________ Never let the truth get in the way of a good story 71 Chev 1/2 ton 4X4 LWB Fleetside SOLD http://67-72chevytrucks.com/vboard/s...d.php?t=361222 http://www.youtube.com/watch?v=1LgREwtDfaA 68 Chev 1 ton flat bed http://www.youtube.com/watch?v=0bO8szzlD4A 56 Chev Handyman Wagon http://www.youtube.com/watch?v=9y-6ddpBTkM http://www.youtube.com/watch?v=lbLzZ7zY8wA 56 Chev Belair http://67-72chevytrucks.com/vboard/s...d.php?t=410667 http://www.youtube.com/watch?v=xoW0Ei7ZNIg Last edited by oldiron; 09-22-2003 at 02:26 PM.

09-23-2003, 10:24 PM	#11
Orence1 Registered User Join Date: Jan 2000 Location: Bothell, WA Posts: 548	Put the rear wheels up on jackstands tonight, ran it up to 2500 RPM which has really caused vibration and there was nothing. I am assuming that it is not the driveshaft and I need to take a harder look at tires and suspension. Thanks to all of you who shot off some excellent suggestions. Larry



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