Shaking rear end

I've had this exact issue with a couple different trucks due to out of round drums or the balance weight falling off. If the drums were stored or shipped on their sides, they will go slightly out of round and cause this. I've had good luck with Napa drums only. Other brands are hit and miss. I would suggest having the axles checked by a shop to make sure they are in the tolerance range. Have the drums checked as well and replace them (and have those checked) if needed.

scott2093 said:

When did the shaking start? Was the shaking the reason for the u-joint and driveshaft replacement?
What kind of replacement parts? Who did the work?
Bounce?Shake? Not sure what to make of that description. Anything you can compare it to?.... like...going over the rumble strips on the highway...etc...

Click to expand...

It started just before getting my new tires and drum brakes. I had my mechanic replace the U-joints. I used Precision U-joints from Orielly as replacements. I'd say more of a bounce for sure, like an unbalanced tire even though I have rotated my tires and the bounce remains the same. It is coming from the back of the truck because I feel it in the seat, not from the steering wheel.

jakeboyce33 said:

It started just before getting my new tires and drum brakes. I had my mechanic replace the U-joints. I used Precision U-joints from Orielly as replacements. I'd say more of a bounce for sure, like an unbalanced tire even though I have rotated my tires and the bounce remains the same. It is coming from the back of the truck because I feel it in the seat, not from the steering wheel.

Click to expand...

Any more trial and error since ? Ruled out any of Hipster's advice in post#10?

Still say the driveshaft needs inspected for ANY problems.

jakeboyce33 said:

The truck shakes at 47-53mph and at 67-74mph.

Click to expand...

Greetings jakeboyce33,

Tough vibration issues that resist normal corrections (tire rebalancing, shock replacement, etc) can
be fixed, but it will require careful observation by you, for both when the vibration is present *and* absent.
Good on you for observing that the vibration comes, goes, and returns. More on this in a bit.

When looking for the source of a vibration, they can be divided into 3 main categories. Figuring out which
category the vibration falls into will help tighten the problem description, lessen the real estate we're focused on,
and get us barking up the right tree so to speak. Here are the categories:

* Vibration is engine (and/or accessory) speed related
* Vibration is driveshaft/road speed related (with no torque / acceleration / deceleration)
* Vibration is driveshaft/road speed AND torque related (vibration worsens with acceleration)

NOTE: There can be some of each of the 3 categories above. For example, a small vibration in
the serpentine belt driven accessories and a small imbalance in the driveshaft can add (reinforce)
and subtract (cancel) each other, with this being rpm / frequency-dependent.

In order to keep this reply from becoming too long to read, I'd like you to try the following and
report back with your observations:

Q1) Drive through the vibration speeds as you normally would in order to establish a baseline.
Now accelerate to just above the highest speed, and then put the truck in Neutral and allow
the engine to idle while the truck coasts back down to ~40 mph.

Q2) When the truck coasted through the vibration speeds, were the vibrations still present, or
were they much less?

Q3) Does accelerating through the vibration speeds make the problem worse, or no change?

Q4) Assuming a gear change, is the engine rpm the same at the 47-53 and 67-74, or not?

Q5) Is your truck lifted? If so, what are the angles that the u-joints in your driveshafts are
running?

Q6) Has the truck recently been in an accident?

Q7) Has there been any catastrophic powertrain failure that has been repaired?

Q8) Has the truck ever driven smoothly at these speeds during your ownership? If so,
how long ago was this? And what exactly has been changed since then?

****

Quick personal story. I had a 3 year old car that ran well without any vibration at any speed.
On a 2-3 upshift I grenaded the rear end. So I purchased a brand new stronger rear end
from the motorsports division of Brand F. Subsequent to the replacement I now had a
vibration at 75+ that resisted repair. This was pre-internet, so all I had was the factory
service manuals.

After spending a lot of time & effort trying to troubleshoot the replaced differential, it turned
out that when I grenaded the previous differential I also twisted the driveshaft a little. (maybe 10°)
It wasn't easy to see, but when placed on a long, straight workbench surface it was obvious that
the front & rear u-joints were no longer working in the same plane. (The driveshaft wouldn't sit
flat on both u-joints, but instead rocked between the two.)

Replacing the driveshaft cured the vibration. (And the lesson that it takes a long time to fix something
that isn't broken was reinforced to yours truly yet again. :0)

jakeboyce33 said:

I also had Goodyear Ultra terrain tires put on in before winter. I've had them re-balanced and the rear end still shakes. Rims are stock size and still in good shape. Every once in a while while going 70mph it's as smooth as a babies bottom going down the road but the bounce eventually comes back. Wheels are tight, I've swapped the front tires to the rear on both sides, on the side it shakes the most I tried a different drum and it still bounced/shook. It's a solid rear axel back there. I'm not sure what else to try at this point? Any advice is appreciated, this is driving me nuts!

Click to expand...

OK, this is good data. Life is easy when a vibration is only being generated from one root cause.
It is a lot harder when 2 small vibrations are reinforcing and cancelling each other, depending upon
the speed of the engine / accessories vis-a-vis driveshaft/road speed, and torque as a third variable.

****

I've always had an interest in automotive NHV (Noise, Harshness, & Vibration) ...and I value something
like an old GMT400 chore truck that runs very smoothly at all combinations of speeds & loads.

For me, few things are more off-putting than a vibration at speed. (!) The good news is that GM Factory
Service Manuals have one of the very best Vibration Diagnosis sections of anyone, anywhere. I've attached
just a couple of pages to pique your interest. If you haven't already done so, then go to this forum's FSM
cache of links that allow you to download these manuals. (88+ Factory Service Manuals)

I guarantee that if you download the applicable manuals for your vehicle and study the Vibration section,
between this and the combined experience in this forum that you will be able to track down & eliminate
those vibrations.

Please evaluate your truck based upon the questions above and reply to this thread with the requested
info. This way we can kick this around and come up with some reasoned suggestions. Sharp photos &
even video are very helpful for those of us trying to assist remotely.

Happy vibration Hunting --

jakeboyce33 said:

It started just before getting my new tires and drum brakes. I had my mechanic replace the U-joints. I used Precision U-joints from Orielly as replacements. I'd say more of a bounce for sure, like an unbalanced tire even though I have rotated my tires and the bounce remains the same. It is coming from the back of the truck because I feel it in the seat, not from the steering wheel.

Click to expand...

Is there a bit more to this story?
Two things that stand out to me,
"I had my mechanic replace the u- joints"
"I used precision u-joints from Orielly"
Who is your mechanic and why did he let you provide the parts?
No shop on earth that has any sense will install customer supplied parts.
If they do, chances are that they are not mechanics but more like people who happen to own wrenches.
Who diagnosed the bad U-joints and how were they determined to be bad?
Was the pinion bearing checked?
Was the driveshaft marked to the yoke before the joints were replaced or is the shaft 180 degrees out of phase.
Is there any oil in the diff?
Is that oil burnt or full of water?
Is your gear set locking and unlocking on you?
Does this truck have a G80 diff?
Do you have a bad shock on that side and a good shock on the other side?
Do you have a broken spring in the pack or a broken spring pin or a broken spring u bolt or bad bushings and the differential is wandering around on you?
Did your same mechanic do the brakes the first time and then you put a different drum on it or did he do it with the drum you gave him.
Does this guy actually know how to do drum brakes and adjust them correctly?
Tire balancing is a also a potential problem.
285/75/16 or pretty much any 16 inch tires are getting hard to find these days.
Before you drop a thousand bucks on a set of tires you need to inspect that set of tires.
Especially in a small town or a small shop.
Those big heavy tires may have been standing on a tire rack for years waiting to be sold.
You need to look them over and look at the date code.
The other problem is that getting a heavy truck tire that has been sitting for a long time to balance is a bit more involved.
What they should do when a big tire is close to being unstable is unseat the tire and rotate it on the rim and then try again.
You repeat that process as many times as it takes to get the wheel weights as low as you can.
Any good 4x4 shop understands that.
Take a look at your "balanced" tires.
How many wieghts do you see on the inside of the rim and the outside of the rim?
Do you have aftermarket alloy rims and they put clamp weights on them and the tie rod end knocked them off?
Did you have that balance re- checked by the same guys who sold you the tires?
Did you take your truck to a "mechanic" with a problem and he didnt know what he was doing but charged you a lot of money and now he throws his hands in the air like maybe its your fault and he has no warranty and wont answer the phone and now you are here
You have come to the right place.
You have nothing to fear about when trying to repair a car.
The worst that can happen is you break something and have to fix it.
The part you need to learn is how to jack a car up and support it so it doesnt drop on your head and how to not launch it through your house.

Does it vibrate when you put it in neutral while at those speeds?

Also Jack up the truck so the rear wheels are off the ground, on Jack stands with the front wheels well chocked. Run the car in gear and watch for “run out” on the tires as they rotate. You can also check with it in neutral shut off. Rotate the tires by hand and check to see if they are running true up and down.

It’s best to have someone in the truck to use the brakes if needed.

My Trailblazer has had repeat problems with "twerking", shaking from the rear most-pronounced at ~73 mph. Started at 68, and was gone again at 80. There's no use looking in the rear-view mirror at 73, though. Nothing but a blur.

Both times, the problem was the driveshaft. First was the rear U-joint which I diagnosed--the cross was visibly damaged; but I had a driveshaft shop replace it. They put the shaft on a lathe. They replaced both U-Joints, and claimed to "straighten" the shaft to within .020. The repaired shaft totally eliminated the vibration, including minor vibration as low as 20 mph that I didn't know was there until it was GONE. I thought it was the result of rougher-than-optimum roads. Nope.

A year or two later, it was back. I replaced the driveshaft with a Treasure-Yard shaft, which I pounded a rear U-joint into. My experience is that on rear driveshafts, the rearmost U-joint is about three times as likely to fail as the front U-joint. Again, vibration totally gone including at low speed which I didn't notice until it vanished.

I've got that same vibration again, after a couple of years. I was considering that the bushing in the transfer case was getting worn; or there were problems with the rear axle. But the engine popped at 280K, and I don't seem to have the ambition to replace it. So it's unlikely that I'm going to track down that vibration again any time soon.

thinger2 said:

Is there a bit more to this story?
Two things that stand out to me,
"I had my mechanic replace the u- joints"
"I used precision u-joints from Orielly"
Who is your mechanic and why did he let you provide the parts?
No shop on earth that has any sense will install customer supplied parts.
If they do, chances are that they are not mechanics but more like people who happen to own wrenches.
Who diagnosed the bad U-joints and how were they determined to be bad?
Was the pinion bearing checked?
Was the driveshaft marked to the yoke before the joints were replaced or is the shaft 180 degrees out of phase.
Is there any oil in the diff?
Is that oil burnt or full of water?
Is your gear set locking and unlocking on you?
Does this truck have a G80 diff?
Do you have a bad shock on that side and a good shock on the other side?
Do you have a broken spring in the pack or a broken spring pin or a broken spring u bolt or bad bushings and the differential is wandering around on you?
Did your same mechanic do the brakes the first time and then you put a different drum on it or did he do it with the drum you gave him.
Does this guy actually know how to do drum brakes and adjust them correctly?
Tire balancing is a also a potential problem.
285/75/16 or pretty much any 16 inch tires are getting hard to find these days.
Before you drop a thousand bucks on a set of tires you need to inspect that set of tires.
Especially in a small town or a small shop.
Those big heavy tires may have been standing on a tire rack for years waiting to be sold.
You need to look them over and look at the date code.
The other problem is that getting a heavy truck tire that has been sitting for a long time to balance is a bit more involved.
What they should do when a big tire is close to being unstable is unseat the tire and rotate it on the rim and then try again.
You repeat that process as many times as it takes to get the wheel weights as low as you can.
Any good 4x4 shop understands that.
Take a look at your "balanced" tires.
How many wieghts do you see on the inside of the rim and the outside of the rim?
Do you have aftermarket alloy rims and they put clamp weights on them and the tie rod end knocked them off?
Did you have that balance re- checked by the same guys who sold you the tires?
Did you take your truck to a "mechanic" with a problem and he didnt know what he was doing but charged you a lot of money and now he throws his hands in the air like maybe its your fault and he has no warranty and wont answer the phone and now you are here
You have come to the right place.
You have nothing to fear about when trying to repair a car.
The worst that can happen is you break something and have to fix it.
The part you need to learn is how to jack a car up and support it so it doesnt drop on your head and how to not launch it through your house.

Click to expand...

I work out of my garage at home and I install customer parts. There is a caveat though. They have to be parts that I choose and not them. I do not make money on the parts and I do not warranty the parts at all. I have only had one new thermostat that I installed, stick open and the customer got mad when I said I would charge labor for the repair again. He called me names and threatened to "tell everyone" and I said "go ahead" and kicked him out of my driveway. He knew all my rules up front and agreed. Have not heard from him in over a year.

By the way, I had asked early in this thread to get the driveshaft checked for phasing and impact and balancing problems and as of yet, I have not seen where the OP responded back about the driveshaft.

movietvet said:

I work out of my garage at home and I install customer parts. There is a caveat though. They have to be parts that I choose and not them. I do not make money on the parts and I do not warranty the parts at all. I have only had one new thermostat that I installed, stick open and the customer got mad when I said I would charge labor for the repair again. He called me names and threatened to "tell everyone" and I said "go ahead" and kicked him out of my driveway. He knew all my rules up front and agreed. Have not heard from him in over a year.

By the way, I had asked early in this thread to get the driveshaft checked for phasing and impact and balancing problems and as of yet, I have not seen where the OP responded back about the driveshaft.

Click to expand...

Yep. The one thing that most people who start their own business miss and really dont understand is that when you start your business with ths best of intentions and because you are an honest man and you think that honesty will see you through.
Your customers are liars.
People will lie like a dog on a rug and tell you they had nothing to do with that never ever oil changed engine and if you swap it out they will be back in a week bitching about how the glove box door wont stay shut and thats why they wont pay the invoice.
Or in Washington State you can buy a 4 bay shop on 5 acres and mechanic lein cars and stack your unpaid bills twenty deep that you cant title or take possenion of and then get shut down by the state for having an unpermitted wrecking yard.
If you decide that you are good enough at whatever it is that you do.
If you decide that you can go out on your own in that business or trade or whatever it is that you really love doing and you are very good at.
You will never get to do that again.

Heres my easy divorce recipe.

Be very very good at what you do.
Let your ego take charge.
Start your own business thinking that you can still go work in the field and be gone for weeks at a time.
Pressure your wife into handling the customers and the insurance and the bills and the kids and the mortgage and the roof leaks and the backed up toilets
I gaurantee you boys that plan will work every damn time.