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Vibration / Shaking side to side Rear 14BFF

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kwissman

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I am getting a bad vibration (side to side shaking) from my rear end at around 65mph and it gets worse if I go faster. I had a friend look at the wheels and the front are running smooth but the rear are shaking. It shakes the whole vehicle from side to side. This is not a driveshaft vibration as I had a stock shaft and now have a CV from HAD and the vibration is the same. The driveshaft vibration went away when the CV was installed and the pinion pointed correctly.

4" DIY4x shackle flip w 6" shackles.
14BFF rear with 4.56 gears, disc brakes (d60 rotors and calipers) and a detroit.
NP241 w JB SYE and HAD Flange
Tires are new 38x12.5-16.5 TSL SX with 14oz of airsoft pellets.
New CV driveshaft from HAD and the pinion is pointed correctly.

I have switched from standard rims to 12 bolt H1s and moved tires and wheels to different positions.

I did not put new wheel bearings on the axle when I installed it.

Any idea what this could be? I have searched multiple sites and found nothing like this. I need to fix it as I have to drive really slow and the others leave me behind when we are headed out to ride and it kills the kidneys.

Thanks for any help Kent
 
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Was this axle recently installed, or has been under the vehicle and driven on before?

You list alot of modifications, were they done all at the same time and then the vibration began?

Just trying to establish a time line as to when the vibration started to help you eliminate things.
 
Kert,

The axle, shackle flip and new tires on the standard type steel wheels were all installed at the same time. I had a driveshaft vibration with the standard driveshaft. And the rear end shaking at about 65mph

I then installed the SYE and HAD CV shaft this spring. The driveshaft vibration went away, but the rear end shaking was still there.

I did the H1 wheels and airsoft pellets a couple of weeks ago and move the tires to differnt positions and the shaking at 65 is still there.

I hope that helps.
 
You said you rotated some tires around so I'm going to say your wheels are OK.

Bent axle?
 
I checked the torque on the U bolts before the last outing. They are tight.

If I pull the axle how can I tell if it is bent.
 
I am having the same exact problem. So yes about the bend. Mine is a 14blt ff out of a 73 suburban 4.56 and lincoln locked. but pretty much the same ole nasty Vibration. One of the ORD boys swears to me its my Angle. I just put in some 5degree shims did not help suggested 8 degree. So I am lost. does yours do it bad on decceleration too. and do you get the loud grrrrrrr sound?
 
Mine is not related to the driveshaft. That vibration went away with a CV shaft and pointing the pinion at the Tcase. Mine more like a side to side shaking coming from the rear of the vehicle. It starts about 65 and will beat you to death by 70. I am going to look into the bent axle idea. Just have to figure out how to check it.
 
TDAWG1 said:
I am having the same exact problem. So yes about the bend. Mine is a 14blt ff out of a 73 suburban 4.56 and lincoln locked. but pretty much the same ole nasty Vibration. One of the ORD boys swears to me its my Angle. I just put in some 5degree shims did not help suggested 8 degree. So I am lost. does yours do it bad on decceleration too. and do you get the loud grrrrrrr sound?
Click to expand...
that sounds like your axle is wraping when you slow down, throwing your pinion angle off and causing vibrations. Mine does the samething and makes the same grrr noise when I exit the highway and slow down. 65 is pretty fast and that usually when tires start showing problems. My dads f250 on 35's would beat the hell out of you once you got over 70, blanced the tires and it kept doing it, had them balanced again and it went away so I wouldnt rule out the tires yet. I would try a different set of tires just for grins maybe...
 
I know my vibe is due to driveshaft.. it shows up at launch... if I take off from a dead stop really hard.. I can actually get the rear wheels to hop off the ground!!!!! :eek1:

it is due to the 2 piece driveshaft and my center bearing only lowered a couple of issues... at higher speeds im fine.. so

id think possibly tires causing your vibration... could you just take them to a shop and have them check the balance on the tires?
 
I do not have a driveshaft vibration and the shaking does not start until 65 mph or so. It is there even if I get off the gas. I have 14oz of airsoft pellets and I don't think that a balance machine will work with the pellets. I have also moved tires around and changed wheels and the shaking is still there. I have to believe that is either bearings in the FF hub or a bent axle.

I will probably change out the bearings this weekend to see if that helps and see if I can figure out a way to check the axle straighness.
 
Check your bearings first and anything else remotely related.

Jack up the rear and remove the cover. Spin the wheels and see what's going on in there.

Checking the axle for striaghtness isn't a fun thing. Exhaust all other possibilites first.
 
I did not get to check the bearings, but I did put the rear up on jack stands and put it in gear to check the driveshaft. There is no visible vibration.

I also tried to move the wheels top to bottom and there was no movement.

I am waiting on the D60 lock nuts to do the bearings. I want to only have one special hub nut tool. Hopefully I can do it this next weekend.
 
my 14bolt is doing almost the same thing. Rides smooth until about 60. Then it seems like the rear is shaking. Mostly on the right side it seems like on mine. But My tires are not balanced at all. Im subscribing to see how this turns out.
 
I replaced the hub bearings on both sides last weekend and the shaking / vibration is still there.

So, I am going to remove the rear driveshaft and take it for a spin to see if it goes away. I am running out of ideas. I am pretty sure my rear shaft angles are correct, but I am grasping at straws at this time.

We are going on a trip on the weekend of the 13th and I would like to have this gone as it is a little over an hour drive.
 
did you ever pull the axle shafts out and check them? Im not exactly sure the best way to do this. But It seems like it could possibly be the problem.
 
Take some measurements with the wheels off. Rear hub to front hub on both sides. Then maybe try squating the rear end down with some ratchet straps and see if you still have the vibs, it might be axle wrap. Do you have monotube shocks or twin tube?

Since its a new axle I'd also get it on some level ground and take measurements all along the axle tube to see if one is bent. its also real easy to pull the shafts and roll them on a flat bench to see if one is tweaked. Where u get the axle from?
 
I pulled the rear shaft and took it for a test drive yesterday and the vibration was still there, so that eliminates the rear driveshaft. I guess I am down to looking at the axle shafts, but not sure how to check them. they do not have a bearing surface near the flange since it is a full floater. It might be cheaper to just get a different set of axle shafts and throw them in.

I did find that the bolts that hold the mount to the transfer case adapter were a little loose, but it did not fix the problem. I am thinking they were loose from the vibrations.

I got the axle from a guy in Copperas Cove that was running it in a M37. He is a pretty serious wheeler and seemed to take good care of his stuff.

On a side note I was planning on going on a run this coming weekend, but I found out when testing with the rear shaft out that my front shaft is toast. The splined area and slip yoke have excessive play and make some horrific noises. The front shaft is now out and pending a new replacement. I am thinking I will look for one of the 1350 ones from an F350. Anybody know what years and models had the 1350 CV shafts on the Furd trucks.
 
Sorry for bringing this old post back to life but i do have the same problem.
Ever found out what caused the vibrations?
 
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