Driveline Vibrations---Possible Driveshaft Issues?

[1998_K1500_Sub]

I have vibration from 60-75 mph consistently.

Any thoughts and opinions appreciated. Thanks for reading.

My random thoughts:

(1) Have the tires been moved-around / swapped side-to-side or front-to-rear, willy-nilly, in the course of work? If so...

It may be your tires' original placement was opportune, and in the course of work they were (re)installed in different locations which caused vibration to become evident.

Consider having the tires checked for radial force variation. I know GM shops can (or did) have this ability on their balancers. I've had my local GM shop (Vaessen Bros, Sublette, IL) balance / check RFV for me, and they use the RFV measurements to suggest the tires' placement on the vehicle so as to minimize vibration.


(2) Is there any chance someone's removed / replaced the driveshaft in the course of work? If so...

At the rear pinion, disconnect the driveshaft and rotate it 180deg. Reinstall. Test drive for vibration change.

I had a guy do rear end work on an S10 Blazer I had (gear swap, one new axle, all new bearings). Immediately after the work I noticed a new vibration, not at low speed but higher (50+ IIRC).

After driving it like this for a few hundred miles, I got the chance to fllp the driveshaft 180deg.

The vibration went away.

Problem solved.

I swear I read about this trick in the GM manual. Well, I'm sure in the manual they say to mark the rear pinion joint before disassembly and be certain to reinstall it the same way.

So when the vibration occurred after the rear-end work, this "swap" was the first thing that popped into my mind.


(3) Check the drums' balance. Their balance likely isn't as crucial b/c their mass is close to the axle, but it's something to check. It certainly can have an effect.

How to check it? I dunno... have a guy chuck-up a drum a tire balancer and give it a spin. If it's true, I would expect it to show on the balancer's results (e.g., little or no weight is suggested to be added). If it's not true... well, adding wheel weights as suggested by a tire balancer isn't an option. One likely drills the drum's rim to balance, so I'm assuming the next step is a trip to specialty shop to balance them... or get replacements that might have better balance.

I hope you find success, regardless.

 

[BBslider001]

My random thoughts:

(1) Have the tires been moved-around / swapped side-to-side or front-to-rear, willy-nilly, in the course of work? If so...

It may be your tires' original placement was opportune, and in the course of work they were (re)installed in different locations which caused vibration to become evident.

Consider having the tires checked for radial force variation. I know GM shops can (or did) have this ability on their balancers. I've had my local GM shop (Vaessen Bros, Sublette, IL) balance / check RFV for me, and they use the RFV measurements to suggest the tires' placement on the vehicle so as to minimize vibration.


(2) Is there any chance someone's removed / replaced the driveshaft in the course of work? If so...

At the rear pinion, disconnect the driveshaft and rotate it 180deg. Reinstall. Test drive for vibration change.

I had a guy do rear end work on an S10 Blazer I had (gear swap, one new axle, all new bearings). Immediately after the work I noticed a new vibration, not at low speed but higher (50+ IIRC).

After driving it like this for a few hundred miles, I got the chance to fllp the driveshaft 180deg.

The vibration went away.

Problem solved.

I swear I read about this trick in the GM manual. Well, I'm sure in the manual they say to mark the rear pinion joint before disassembly and be certain to reinstall it the same way.

So when the vibration occurred after the rear-end work, this "swap" was the first thing that popped into my mind.


(3) Check the drums' balance. Their balance likely isn't as crucial b/c their mass is close to the axle, but it's something to check. It certainly can have an effect.

How to check it? I dunno... have a guy chuck-up a drum a tire balancer and give it a spin. If it's true, I would expect it to show on the balancer's results (e.g., little or no weight is suggested to be added). If it's not true... well, adding wheel weights as suggested by a tire balancer isn't an option. One likely drills the drum's rim to balance, so I'm assuming the next step is a trip to specialty shop to balance them... or get replacements that might have better balance.

I hope you find success, regardless.

I really appreciate the input. Small update. I took it to a real tire shop this morning. They found the drivers side rear grossly out of balance. I was hopeful....didn't work. While the vibration was reduced noticeably, it still has the same characteristics at the same speed. So, all tires balanced and rotated. I then took it straight to the guy who did the rear brakes and seals last month. I noticed two new things. It vibrates in the rear when braking and it vibrates on harder acceleration....like a u-joint. He put it up on the rack and had his helper shift it from R to D. The driveshaft rotates at the pinion about a half turn....dangit. The u-joints look tight....the rearend should not have that much play between shifts. Also, he said he would put the drums on his lathe and mic them out to see if they are warped at all and will replace them either way to make sure they aren't the issue. They are under warranty, so no biggie. He will put it up tonight, watch the drive-train while it turns with the wheels off, and see what he can see. I hope hope hope it's not the rearend....man,so much coin put out this month LOL....I have GOT to get a place I can do my own work. Sheesh!

So, I don't know if the rearend going out could cause all of this. I certainly don't like that the damn DS spins a full half turn when re-engaging....not good.

 

[BBslider001]

Small update....it's at the shop. It's up on the lift and it was started and run in D while we watched it. The DS tire has an up and down bouncy motion. The axle seems true. The PS has a very slight wobbly when looking at the wheel from the front. He also said he ran it up to 65 mph and watched the drive shaft itself. It started vibrating pretty bad where it shook the back of the truck. He did that with wheels and drums removed, and he also replaced the drums with brand new ones. I am at a loss. I even priced out 2 used rear ends on an hour from me at $450, just in case. I'm really trying to narrow it down because I just can't afford to buy all new tires, rebuild the drive shaft, and replace the rear end. Maybe it'll go up for sale and I'll start over. It just really boggles my mind that it didn't do this until after the brake work and axle seals were done.

 

[HotWheelsBurban]

Small update....it's at the shop. It's up on the lift and it was started and run in D while we watched it. The DS tire has an up and down bouncy motion. The axle seems true. The PS has a very slight wobbly when looking at the wheel from the front. He also said he ran it up to 65 mph and watched the drive shaft itself. It started vibrating pretty bad where it shook the back of the truck. He did that with wheels and drums removed, and he also replaced the drums with brand new ones. I am at a loss. I even priced out 2 used rear ends on an hour from me at $450, just in case. I'm really trying to narrow it down because I just can't afford to buy all new tires, rebuild the drive shaft, and replace the rear end. Maybe it'll go up for sale and I'll start over. It just really boggles my mind that it didn't do this until after the brake work and axle seals were done.

Maybe the new parts eliminated the slack in the driveline, that made the vibration not as noticeable?

 

[1998_K1500_Sub]

Small update....it's at the shop. It's up on the lift and it was started and run in D while we watched it. The DS tire has an up and down bouncy motion. The axle seems true.

Weren't the tires recently balanced? Is the DS tire out-of-round? Was something else inciting a bounce in the DS wheel/tire, i.e., was the axle / spring assembly bouncing due to some induced vibration in the driveline, and it was simply noticed as a bouncy DS tire? Read on...

The PS has a very slight wobbly when looking at the wheel from the front.

Wobbly... you mean, like the wheel is bent?

He also said he ran it up to 65 mph and watched the drive shaft itself. It started vibrating pretty bad where it shook the back of the truck.

If it's hanging in the air on a lift, the driveline U-joint angles will be atypically large, and not necessarily complimentary (as they're designed to be with the vehicle on the ground). It wouldn't surprise me if this imparted more vibration to the drivetrain.

Too, with the axle hanging from the springs (and not grounded via the tires to the Earth, as it would normally), the axle / spring system will have its own resonant frequency (like a tuning fork) that might be easily set into vibration at just the right driveshaft speed by the drivetrain vibration I mentioned above.

It just really boggles my mind that it didn't do this until after the brake work and axle seals were done.

I'm not saying that this test was useless. It might be very useful. But I think it needs to be interpreted carefully or it'll send you down a rabbit hole.

You might try running the same test with the rear axle on jackstands and with the weight of the vehicle on the suspension (to get the driveline angles where they belong). The rear axle won't shake much, if at all (it's grounded via the jackstands) but the driveshaft and transmission will (should) vibrate if you've got a driveshaft / U-joint issues.

The wheels/tires and I believe drums can be checked for balance (and the tires for radial force variation) on a wheel balancer. Yeah, I know, one can't balance the drums on a wheel balancer, but that's not the objective; the objective is to see if they are balanced, and I believe that's possible.

 

[BBslider001]

Maybe the new parts eliminated the slack in the driveline, that made the vibration not as noticeable?

You mean the new on the front or the new brakes and drums? Apologies, I am not sure what you mean. Can you reword it? Maybe I'm overtired LOL

 

[BBslider001]

Weren't the tires recently balanced? Is the DS tire out-of-round? Was something else inciting a bounce in the DS wheel/tire, i.e., was the axle / spring assembly bouncing due to some induced vibration in the driveline, and it was simply noticed as a bounce DS tire? Read on...

It "seems" out of round, yes. Suspension was still and the axle is sitting on a stand and block of wood, so the suspension is loaded, if that make sense?

Wobbly... you mean, like the wheel is bent?

Yes, kind of like that, but wasnt bent before if it is bent.

If it's hanging in the air on a lift, the driveline U-joint angles will be atypically large, and not necessarily complimentary (as they're designed to be with the vehicle on the ground). It wouldn't surprise me if this imparted more vibration to the drivetrain.

Too, with the axle hanging from the springs (and not grounded via the tires to the Earth, as it would normally), the axle / spring system will have its own resonant frequency that might (I say "might" because I've not done it myself) be easily excited at just the right speed by the drivetrain vibration I mentioned above.



I'm not saying that this test was useless. It might be very useful. But I think it needs to be interpreted carefully or it'll send you down a rabbit hole.

Man I agree with this 100% !!! Seems a somewhat simple issue is now getting very discombobulated.

You might try running the same test with the rear axle on jackstands and with the weight of the vehicle on the suspension (to get the driveline angles where they belong). The rear axle won't shake much, if at all (it's grounded via the jackstands) but the driveshaft and transmission will (should) vibrate if you've got a driveshaft / U-joint issues.

I wonder if Jack stands would be more stable than the one point it's resting on the diff. I "think" it's about the same. I very much appreciate your input. I will report back tomorrow.

So her is the other thing. Mechanic found a wheel weight on the front and then another weight on the back of the rims opposite of each other ....as in 180*....the very thing the guy at Discount Tire told me should never be done!!!! WTF?? Talk about a rabbit hole. Does no one know how to balance a tire?

 

[1998_K1500_Sub]

So her is the other thing. Mechanic found a wheel weight on the front and then another weight on the back of the rims opposite of each other ....as in 180*....the very thing the guy at Discount Tire told me should never be done!!!! WTF?? Talk about a rabbit hole. Does no one know how to balance a tire?

If they were on the same edge of the wheel (thus rotating in the same plane), yeah, foul…

But on opposite sides of the wheel (rotating in two planes), I think fine.

In the general case, wheel balancing requires weights be added in two planes, e.g., inside edge and outside edge of wheel, but could be on inside of rim too provided the two weights rotate in two different planes. Two planes is a requirement.

Having them opposite each other on opposite sides of the wheel doesn’t seem inconsistent. They’re rotating in two different planes. It’s not like they cancel each other!

In the degenerate case, only one weight situated in the proper plane can yield balance, but that may not be a common occurrence in practice.

 

[Schurkey]

Mechanic found a wheel weight on the front and then another weight on the back of the rims opposite of each other ....as in 180*....the very thing the guy at Discount Tire told me should never be done!!!!

Stop going to Discount Tire. Apparently, they hire untrained/inexperienced staff.

Seventy years ago, when wheel balancing was "single-plane" or "static", there'd be no point to having wheel weights 180 degrees apart. But single-plane/static balancing hasn't been popular or appropriate since the early '70s or perhaps before. Two-plane or "dynamic" balancing is FAR better, and yes, you might end up with weighs 180 degrees apart on opposite sides of the wheel.

 

[Hipster]

Dynamic balancing is far more accurate as stated , most machines will balance in both static and dynamic modes. If you request no weights on the outer wheels it gets balanced in static mode. Wheel weights being 180 from inner wheel lip to outer is not anything abnormal.

A road force balance machine will find a separated belt or out of round problem that a regular balancer won't.

U-joints can be dry, tight, and binding and cause issues. Most mechanics I know will turn new drums and rotors before they ever put them on.