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

Stout72 · 11-21-2003, 12:20 PM

I'm experiencing a cyclic vibration while driving on the freeway. It occurs at about 65mph (not sure of the speed since my speedo is not calibrated for 35" tires), between 3400 - 3500rpm. I can feel it slightly in my feet thru the floorboards, and it sounds like, "a-rum... a-rum... a-rum." It almost seems to go away when I back off the throttle. Anybody have any ideas what this could be?

*MJF* · 11-21-2003, 12:26 PM

I would check the easy/cheap things first. Change the ujoints. Maybe have a shop change them for you so they can check the balance of your driveshaft as well.

We will need a little more info on your truck though. Is it lifted? How do the angles of your driveshaft look? Are they correct for your type d-shaft( CV style or standard two ujoint style)?

Hotrod70C10 · 11-21-2003, 12:49 PM

Sounds like mine before I replaced the u-joints and carrier bearing. If it hasn't done it the whole time you've had the truck I would just mark the driveshaft with chalk and take it apart. I replaced my u-joints at home with a small vice and a couple of sockets. If it has been vibrating since you bought the truck I would take it to a shop like *MJF* said.

Stout72 · 11-21-2003, 01:05 PM

The vibration started just recently.

Truck has a 4"lift, one-piece drive shaft w/standard u-joints. The angles appear to be ok, but I've never checked them. I've had this truck for about a year and a half, guess I need to spend some more time underneath. For future reference, what should the angles be?

8.1PWR · 11-21-2003, 01:14 PM

I don't know what the angle is supposed to be but if it started after the lift was installed you may have to take the drive shaft to a driveline shop and have double cardan joints put in. That helps get rid of driveline vibrations.

oldsub86 · 11-21-2003, 01:20 PM

I would start by making sure the tires are alright. If you know anyone with a similar truck, borrow his wheels and tires for a few minutes and see if you still have the vibration. We did that with my brother in law's truck and basically proved that the wheels and tires were not at fault.

*MJF* · 11-21-2003, 07:51 PM

Here's an explanation about the angles. I'm trying to find a better pic but I can't remember where I saw it.

http://www.4x4wire.com/tech/pinionangle/

Stout72 · 11-22-2003, 01:15 PM

The lift was installed by some previous owner. I can only assume that it was done right back then, but I will check. Tires are new BFG ATKOs mounted back in February, and show no sign of abnormal wear. It's probably a u-joint like you said. Thanks to all.

Martin64 · 11-22-2003, 02:04 PM

I'd check the tire pressure and the balance...

11-21-2003, 12:20 PM	#1
Stout72 Not my good side. Join Date: Mar 2002 Location: Fairfield, California Posts: 222	Cyclic vibration? I'm experiencing a cyclic vibration while driving on the freeway. It occurs at about 65mph (not sure of the speed since my speedo is not calibrated for 35" tires), between 3400 - 3500rpm. I can feel it slightly in my feet thru the floorboards, and it sounds like, "a-rum... a-rum... a-rum." It almost seems to go away when I back off the throttle. Anybody have any ideas what this could be? __________________ 72 Chevy K20 Custom Camper, 350/350, 4" lift, dual shock suspension front & rear. Daily driver and a work in progress. 00 Suburban LT 90 Camaro RS 79 Yamaha XS1100 Special (Ol' Reliable)

11-21-2003, 12:49 PM	#3
Hotrod70C10 Low & Slow Join Date: Dec 2002 Location: Oklahoma Posts: 1,047	Sounds like mine before I replaced the u-joints and carrier bearing. If it hasn't done it the whole time you've had the truck I would just mark the driveshaft with chalk and take it apart. I replaced my u-joints at home with a small vice and a couple of sockets. If it has been vibrating since you bought the truck I would take it to a shop like MJF said. __________________ 70' C-10 LWB Fleetside 4.5/6 drop

11-21-2003, 01:05 PM	#4
Stout72 Not my good side. Join Date: Mar 2002 Location: Fairfield, California Posts: 222	The vibration started just recently. Truck has a 4"lift, one-piece drive shaft w/standard u-joints. The angles appear to be ok, but I've never checked them. I've had this truck for about a year and a half, guess I need to spend some more time underneath. For future reference, what should the angles be? __________________ 72 Chevy K20 Custom Camper, 350/350, 4" lift, dual shock suspension front & rear. Daily driver and a work in progress. 00 Suburban LT 90 Camaro RS 79 Yamaha XS1100 Special (Ol' Reliable)

11-21-2003, 01:14 PM	#5
8.1PWR Registered User Join Date: Nov 2003 Location: Green Valley, AZ Posts: 28	I don't know what the angle is supposed to be but if it started after the lift was installed you may have to take the drive shaft to a driveline shop and have double cardan joints put in. That helps get rid of driveline vibrations. __________________ 1970 Chev C20, 2wd, LB, 350 4BBL, muncie 4spd, 4:10 limited slip. 2002 Chev 2500HD 8.1L Allison, 4X4. 1996 Chev S10 Blazer, 4X4. 2006 Jeep LJ Rubicon

11-21-2003, 01:20 PM	#6
oldsub86 Registered User Join Date: Dec 2002 Location: Canada Posts: 695	I would start by making sure the tires are alright. If you know anyone with a similar truck, borrow his wheels and tires for a few minutes and see if you still have the vibration. We did that with my brother in law's truck and basically proved that the wheels and tires were not at fault. __________________ 1968 Chevy - 292 with a powerglide

11-21-2003, 12:26 PM	#2
MJF No longer truckless Join Date: Mar 2002 Location: Campbell, CA Posts: 299	I would check the easy/cheap things first. Change the ujoints. Maybe have a shop change them for you so they can check the balance of your driveshaft as well. We will need a little more info on your truck though. Is it lifted? How do the angles of your driveshaft look? Are they correct for your type d-shaft( CV style or standard two ujoint style)?

11-21-2003, 07:51 PM	#7
MJF No longer truckless Join Date: Mar 2002 Location: Campbell, CA Posts: 299	Here's an explanation about the angles. I'm trying to find a better pic but I can't remember where I saw it. http://www.4x4wire.com/tech/pinionangle/

11-22-2003, 01:15 PM	#8
Stout72 Not my good side. Join Date: Mar 2002 Location: Fairfield, California Posts: 222	The lift was installed by some previous owner. I can only assume that it was done right back then, but I will check. Tires are new BFG ATKOs mounted back in February, and show no sign of abnormal wear. It's probably a u-joint like you said. Thanks to all. __________________ 72 Chevy K20 Custom Camper, 350/350, 4" lift, dual shock suspension front & rear. Daily driver and a work in progress. 00 Suburban LT 90 Camaro RS 79 Yamaha XS1100 Special (Ol' Reliable)

11-22-2003, 02:04 PM	#9
Martin64 Registered User Join Date: Oct 2003 Location: Yuma, Az Posts: 477	I'd check the tire pressure and the balance... __________________ Martin Gibson USAF Retired 1964(-ish) C10 Last edited by Martin64; 11-22-2003 at 02:08 PM.

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