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Suburban bouncing going down the highway and I can't figure it out. Fixed it!

eodcoduto

eodcoduto

We could have been closer.
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Muscle Shoals, AL
The Suburban has a bad bounce from 35-45 and anything above 58 mph, bad enough the seats shake and I can't figure it out. Here is what I've done the last 6-8 months:

New rotors, calipers, pads, rear wheel cylinders and shoes 2 months ago.
All ball joints, tie rod ends, and drag link, Moog.
Redhead steering box.
All front bushing replaced last month with poly, sway bar too.
Wheel bearings and seals when I did the front brakes.
Bilstein 4600 shocks 18 months ago. They act right going over speed bumps and hitting holes in the road, they don't continue to rebound.
New Dorman Ford 16x7 wheels, last month.
New Goodyear tires, last month. All balanced well with the heaviest at 3.5oz and its on the passenger rear.
Left rear axle shaft and bearing 2 weeks ago.
Rear bushings are OEM and need replaced, I have the poly replacements on the shelf but I need to do it.

The brakes also grab in the front frequently, especially when I’n turning into a parking spot and I get pulsing from the rears but both of these are intermittent and I can't predict when it happens. I pulled the calipers last night and my wheel bearing are good and there isn’t any play.
I've jacked up the rear and ran it in gear and there isn't much out of round on the tires, some but very little. The fronts spin smooth
I had a set of Cooper Discoverer AT3's put on in October and Cooper warrantied them when I sent them back 4 weeks ago, they were out of round and the belts separated from the case. One took 14oz to balance, so I don't know if the Suburban caused that or they caused something to go wonky, but this thing has bounced since I got it 2.5 years ago.

I'm about over it, and it's my daily driver with a 39 mile round trip daily, 45 if I go into town for lunch so I can't have it down for a rear end swap or anything major more than a weekend.

View attachment IMG_2351.mov
 
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I wonder if a drive shaft is out of balance. Those things turn at a serious clip. Sounds like you’re getting into harmonic frequencies at those speeds on whatever is unhappy.
 
soft brake lines are getting ready to fail. probably a loose flap of hose intermittently blocking the fluid flow. How many sets of wheels has this "bounce" carried through ? 2 piece drive shaft ?
 
2.5 sets of wheels, one piece shaft its a 91 v2500. The front brake hoses are 2 years old but the rear is the original.
 
You know what. After thinking about this, have you checked the runout on the rear axle flange?
 
The left rear axle flange was warped so I replaced that axle and eyeballing the passenger side. It’s not as bad, but I need to put an indicator on it.
 
No lift it is bone stock with two 265/75-16’s. This isn’t a vibration, its a bounce/shake. The transfer case shifter and column shifter all smooth going down the road so it’s not vibration coming through them. No shake in the steering. So it’s definitely something in the rear end.
 
This thought might be WAY out there but if it has a Gov-Lok rear diff the fly weight might be kick’n out at speed and causing some weird harmonics since they were never designed to be engaged at those RPM’s - the slight push/pull in a slow turn might be when it’s disengaging ?
The springs and governor may need attention to keep the weights from flipping out at speed instead of how it was intended to work - just a thought and something to consider.
 
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Thats worth looking at, when its up on stands and in gear it kicks in and out and clunks when you hit the brakes. I noticed that checking the wheels.
 
eodcoduto said:
Thats worth looking at, when its up on stands and in gear it kicks in and out and clunks when you hit the brakes. I noticed that checking the wheels.
Click to expand...
If it’s doing that it’s working on dying and time to do something about it before the big BOOM happens.
Back in the early 90’s I recall a K-10 come in the shop with a similar complaint and it took a while but the shop owner/mechanic finally found that it was the defective fly weight - R-n-R’d it and no more problems.

Not say’n that’s all that’s goin on with yours but definitely worth look’n into.
 
If it turns out to be necessary, get another axle and go through it, get it ready to go in. Have new u bolts on hand, maybe a new u joint. Swapping is then a Saturday afternoon event, drive some Sunday, and ready to go Monday.
 
I’m at a loss with this one. The driverside has the new axle, bearing, wheel, and tire and you can see it bouncing, and it did the same with the front right wheel on there. The passenger side has .008” of runout but the surface is pitted so I’d call it less than .005”.

First video is the passenger side with the stock axle. 2nd is the driver side with all the new parts.

View attachment IMG_2547.mov
View attachment IMG_2548.mov
 
New shocks too?
I don’t remember reading if there were or not.
I was driving for work today, watch a POS Chevrolet Corsica in front of me hopping along with what I believe was a bad set of shocks.
 
Wes Harden said:
soft brake lines are getting ready to fail. probably a loose flap of hose intermittently blocking the fluid flow. How many sets of wheels has this "bounce" carried through ? 2 piece drive shaft ?
Click to expand...
This would be my vote. My truck had a noticeable "bounce" for some time. I thought it was bad calipers because the front brakes were getting hot. Turned out that the soft brake lines were going bad and acting like a check valve, holding hydraulic pressure on the rotors. It's easy to check, just hit the brake pedal a couple times and see if the front tires still spin easily.
 
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