shudders at 70

[acl]

going to and fro the midwest truck meet in kc this weekend and my truck had a shudder that started at 55 and got worse the faster i went. Had wheels and tires balanced and helped a bunch but still have a shudder that starts at 70. not as bad as before but still there. I have fairly new drums on the back, can those be balanced? anyone heard of that? I am sure they are not all perfect when they cast them, just did not know if that can be checked. I plan on having driveshaft balanced (anyone know where this can happen in kansas or kc mo.) also might put a diff. set of wheels and tires on just to see if they are not right yet. Am i missing any other possibility that you have had?It is not real bad thru the steering wheel so i don't think it is up front. Thanks for the help. Gary

[lowriden58]

where does it feel like its coming from, front or rear? might be driveshaft out of balance/u joint bout to go bad. front end alignment might be off

[steelhorse]

Your drive line could be out of align.Worn motor mounts/trans mounts or lowering a vehical causing improper pinion angle can cause vibrations.

[cdowns]

worn trailing arm bushings or for that matter any suspension pieces or alignment out of wack can cause vibrations

[68gmsee]

Another thing that can cause that is tires (slipped belts). Check all of the above suggestions and try to isolate it. I had a bad tire that gave me similar symptoms and found it by rotating tires front to rear.

To answer your question about balancing. If you go to a reputable machine/alignment shop they can balance drums, etc. May have to shop around for that.

However, it may be possible to balance the tires while mounted on the truck but, I haven't seen that procedure done in a long time.

[ChevLoRay]

There was a time when you could get your wheels balanced on the vehicle. That action was supposed to take into account the tire, wheel and brake drum/rotor, all as rotating assemblies.

I would start out by doing as others have suggested in rotating the tires and checking them for out-of-round, FIRST. After that, I'd look at the driveshaft....U-joints and center support bearing. Does your truck have a squeak-squeak-squeak as you back it up slowly? That is a real good indication that it would have a bad U-joint.

As to the state of balance of the rotors and/or drums, my book isn't on them. What is it about that component that can change its state-of-balance over time? In theory, the tires shouldn't need to be re-balanced, but we all know that worn components of the suspension system can make them bounce ever so slightly as the vehicle rolls down the highway. That can lead to flat spots, cupping, etc. An out of alignment condition can cause wear that also leads to the same symptoms. Have a friend follow you down the highway at the speed that you notice the irregularity and see if he/she can see any up/down movement of a tire/wheel ass'y.

Finally, I had a tire on my Tundra that was bouncing and driving me nuts. I even had two of them replaced under warranty because they were out of round. When the bouncing continued, I replaced all four, with a higher grade of tire. Still had the bounce. My right rear shock was the problem. Replace both rear shocks and the problem went away. Dang! Coulda save some bucks on the tire upgrade, but I also have to say that the tire people coulda seen the bad shock and not done the warranty tire exchange, too.

Live and learn.

[JDahl]

When I worked in Topeka, I would take my driveshafts to Meinholdt's Welding & Machine 1900 NW Central Ave Topeka, KS (785) 234-5221 They always did a great job at fair prices. Even if you just replace your u-joints, you should have the shaft balanced.

[acl]

thanks for the imput, here an update to help, motor mounts are tight and brand new, i do not have a bad vibe. in the steering wheel but it can be felt there just like the rest of the truck, it does drive straight and u joints are a couple years old but very few miles 1000 or less. i have called people that turn drums but so far none can balance them. thanks and keep the ideas coming. gary

[68gmsee]

If it is coming from the rear area, you would feel it all over as you mentioned. My feeling is that it's not the drums, though.

I've had most of the problems already mentioned and can usually tell if it's in the front or rear of the vehicle strictly from the way it vibrates. So, by rotating tires to the front one at a time or both at the same time, you can isolate the tires fairly easy. The vibration would then be mostly felt in the front and on the steering wheel.

As it is, it could be the rear tires or drive shaft. It's easier to check the tires. And, they can be bad even if they look good or are fairly new.

[Blue'72]

When I worked at a tire store years ago, I learned that you don't get as good of balance on the tires if the wheel weights are pounded only on the inside rim. With nice wheels, you wouldn't want them pounded on the outside rim, but the next best thing is to have sticky weights put as far to the center of the wheel as possible. Something to consider about with the tire balances. Also, we would always spin them a couple more times to make sure they keep coming up with zeros after balancing.

[acl]

Originally Posted by JDahl

When I worked in Topeka, I would take my driveshafts to Meinholdt's Welding & Machine 1900 NW Central Ave Topeka, KS (785) 234-5221 They always did a great job at fair prices. Even if you just replace your u-joints, you should have the shaft balanced.

was on the phone with them when you posted, thanks. He said no prob with the shaft and hated doing the drums but would for a price. sounds fair-I think?

[Sammy]

If I bet money I would say the shaft. But with it noticable at higher speeds a belt inside a tire could also be the culpret too.

[Blazer1970]

Bad tire.

[Highsteel]

If you rub the tread area of each tire with the palm of your hand you can detect a bad belt. A severely separated belt will show as a bulge but in the early stages of separation part of the tread will shift to one side or the other. I have found this to be most evident tho when just barely rolling.
Another culprit could be tie rod ends. When they start to wear they allow the front wheels to wiggle at different speeds, depending on the amount of wear. I would check the entire steering linkage for wear(looseness).

[ChevLoRay]

I still say it won't be the drums. What can change to make one become out of balance? Unless you are a fanatic and prone to want to balance every single rotating component, you're gonna throw away some money. When the guy says he really doesn't want to balance the drums, pay attention.

I also contend, as have others, that the tires are the first place to check. Also look at the shocks very carefully and be sure that one of them isn't leaking, or otherwise doing its job very poorly.

So, tires and shocks.

Or, as I was told when I had my stroke and the radiologist said, "Hydrocephalus"....my physicians assistant brother-in-law said..."Don't look for zebras when you hear hoofbeats".

Brake drums are zebras.

[Boog]

Wheels, tires, shocks, u joints are the usuall places to start. So far no one has mentioned pinion angle or worn tailshaft bushing or yoke splines as possibilities. All three of these can give the same symptoms. Another item that comes to mind is the fan clutch and blades. Believe it or not they can cause some wierd vibrations.
Is this vibration rpm specific or only speed specific?

[johny1i]

Swap the u-joints--inexpensive way to eliminate a likely culprit. I went through this for the last couple of months, had the tires rotated/balanced and was very particular with the tech who did it, and still couldn't eliminate the vibration that started at 50 mph. Replaced both u-joints (4x4 with no swing bearing) and she's smooth as silk to 70 mph (which is screaming with my gear ratio). I like the Brute Force u-joints from Advance--lifetime replacement warranty and only ~$15 each.

[acl]

Originally Posted by ChevLoRay

I still say it won't be the drums. What can change to make one become out of balance? Unless you are a fanatic and prone to want to balance every single rotating component, you're gonna throw away some money. When the guy says he really doesn't want to balance the drums, pay attention.

I also contend, as have others, that the tires are the first place to check. Also look at the shocks very carefully and be sure that one of them isn't leaking, or otherwise doing its job very poorly.

So, tires and shocks.

Or, as I was told when I had my stroke and the radiologist said, "Hydrocephalus"....my physicians assistant brother-in-law said..."Don't look for zebras when you hear hoofbeats".

Brake drums are zebras.

I agree with the drums being far fetched, but being i was driving 100 miles with the drive shaft, did not want to go twice. Any type of cast can have air pockets and such, just trying to cross 2 things off the list, thanks for the help. does go back to tire shop today. Gary

Also just now getting up to highway speeds( and beyond ) so i could have had this problem during build just now finding it Thanks

[acl]

Originally Posted by Boog

Wheels, tires, shocks, u joints are the usuall places to start. So far no one has mentioned pinion angle or worn tailshaft bushing or yoke splines as possibilities. All three of these can give the same symptoms. Another item that comes to mind is the fan clutch and blades. Believe it or not they can cause some wierd vibrations.
Is this vibration rpm specific or only speed specific?

It is speed specific, also have changed to electric fans, have had same fan clucth prob on different truck though, thanks for the advice. Gary

[acl]

OK so far tires and wheels balanced and checked twice. Drive shaft balanced and still have the shudder. Today going to measure and laser drive line for alignment, Am still looking for other imput. Thanks for the help so far. Gary

[haysonj]

I don't know if your drive shaft has ever been shortened or lengthened but if it has I would look at the ujoint phasing

[ChevLoRay]

You said it is speed-specific. Do you have a tach and are you able to determine the rpm at which it happens? Since you seem to have eliminated everything else from the driveline and chassis, what are the chances that it may be related to the rotation of the engine/transmission components, like maybe even an output shaft issue with the gearbox?

If you are anal like I am about nagging stuff like vibrations and rattles, you won't rest until it kills you or you find it and fix it.

Good luck.

[steelhorse]

If you are feeling it in the front it could be a shock,if one is week it can let the tire bounce at higher speeds.If it feels like the rear I would say check your pinion angle.especially if it is lowered.

[Brad]

I have a similar issue in my '68. I went to the tire store twice recently and had them balance the the tires. The second time I explained what I was dealing with and they did two things which helped: put weights on the outside of the wheels instead of just the inside, and most importantly the guy rotated 2 tires on their rims to balance better. I still have the vibration but not as bad.

[DA68]

Gary,
I'm inclined to think you may have a tire or wheel issue. I worked in the automotive industry for 10 years and a large part of my job was ride evaluation. Your tires and wheels may balance out okay, but that does not mean they are uniform (perfectly round/centric). I would check the Tire Rack's website for their "preferred installers" in your area and call to see which one has a Hunter 9700 RFV machine. This machine can check the uniformity of the tires, wheels and the entire assembly. While this machine was discounted by many in my industry, because it was not to the level of a $250,000 lab machine, it is still a great resource in pinpointing a problem tire or wheel.
Make sure there are no burrs or gouges on the mounting surface of the wheels and your rotors or drums. This area, where the wheel and vehicle meet is critical and should be void of any protrusions. Same goes for the center bore of the wheel (area that fits over the hub of the wheel).
Are you running aftermarket aluminum wheels? Please ensure they fit the hubs correctly and that the lugnuts are correct for the wheels.

If the driveshaft has been balanced and the U-joints tight, you should check your transmission mount and then shocks next.

Try to think back to any changes you may have made that could have caused this issue. If you are sure this issue happened after your rotor/drum change, let me know as I've got means to check them also.

When you find the culprit, please share with us and good luck!!!
Dave