Help with terrible vibration....

My signature is accurate to my current truck. So to start off I have a low grumble that starts at like 50 MPH. At around 63 it starts to get very noticeable, between 68 and 73 its a very high frequency vibration that you can feel in your seat and the floor. At 73 it is gone completely. The truck is smooth as glass afterwards. You can never feel it in the steering wheel or the pedals.

In 4wd high range you cannot go over 15 without a horrible vibration.

In 4wd low its barely noticeable and you can run right up to 4th gear with just a hint of the noise.

If I let off at over 73 when the vibration is not present it will coast down without the vibration ever occurring.

If I let off when the vibration is happening it will continue until the truck slows down sufficiently.

We have changed the U joints and cardigan joint.

Removed the front driveshaft

removed the rear driveshaft

split the transfer case and went as far as removing the chain and shaft. There was very little metal and the bearings we got to seemed to be in great shape. Without knowing if maybe the chain was jumping we put a brand new chain in. The plastic on the shift forks was great and I was able to free up the shift linkage. (if you have trouble with a stiff t-case shifter mine was seized where it goes through the case I was able to use a punch to remove it and clean it up now it shifts very easy.)

The tires have been balanced and rechecked and lug nuts all are tight.

I was hoping someone would have an Ahh-ha! this is what that has to be moment. Because I am at a loss! Thanks!

I’d check diff fluid, hubs and axle shaft u joints

I checked the rear, have not checked the front. Thank you.

I had very similar symptoms with a 98, it was my old work truck and just dealt with it. After awhile the pinion seal on the rear started leaking bad, pulled the yoke to change the seal and found the pinion bearing was shot. It ate up the gears from the pinion being loose so I swapped in a used rear. Vibration was gone after

Has it always done this or is it a new thing? If it’s new, what did you mod/change before it started?

Rim center probably twisted, 2 piece driveshaft

And the long, long shot would be the harmonic damper.

I've had something similar when my carrier bearing on the rear 2pc driveshaft was going.

It says you've removed the rear driveshaft. How did you drive it like that? Did you make a plug for the rear of the t-case?

The 4WD aspect of it makes me think it should completely go away when you drive without the front driveshaft.

Never noticed anything in 2wd, but my front pionon bearing went out once, could doing anything above an idle in 4wd, or ot made a horrible noise.

Sent from my SAMSUNG-SM-G930A using Tapatalk

Pull the CAD apart and inspect it.
Mine went to **** after low fluid and my learning curve killed the bushing, pads and seals that support the axles. My vibration went away somewhere in the course of Ford hubs and a cad delete shaft.

Sent from my XT1575 using Tapatalk

How are you’re front wheel bearings? Also check the wear on your brake pads to make sure you don’t have a slight drag.

Well, did you find it. I have the same issue at 85+

New U-Joints, New center bearing, drive shaft balanced. Wheels balanced, brakes good, rear end good........I'm so confused! LOL!

did the OP ever consider T case rubber mounts?

Same problem have yet to pin point mine either

Food for thought, that little pin that the calipers slide on, that your supposed to re grease each time you change your pads....ummmm yea...this guy (me) yea over here...lol I forgot to do that.

Vibrations above 55 til about 68 where is was really noticeable. Then when braking, between 50-40 really bad vibrations.

Out of nowhere I remembered about 5k after doing the pads, it hit me, I tore it down and re greased the pins...

BAM...no vibrations!!!

Just food for thought

Update on mine.
I was under the truck the other day and had the U-joints parallel to the ground, took a close look and noticed that the rear most joint was about three degrees off from the front one. Fully rebuilt drive shaft is twisted about three degrees...Bummed.
I will be installing a new one piece drive shaft this summer at about the same cost as it cost me to have the one under my truck rebuilt a year and a half ago......at 6-700.
More money down my money pit of a truck.....I want to drive my Geo metro, it never breaks, but it can't tow anything. LOL!

The u joints being out of phase will cause it. I had one built by a local hd truck shop for a swap. And it had a horrible vibe. They made it right and fixed it and the vibration went away.

bwdt said:

Update on mine.
I was under the truck the other day and had the U-joints parallel to the ground, took a close look and noticed that the rear most joint was about three degrees off from the front one. Fully rebuilt drive shaft is twisted about three degrees...Bummed.
I will be installing a new one piece drive shaft this summer at about the same cost as it cost me to have the one under my truck rebuilt a year and a half ago......at 6-700.
More money down my money pit of a truck.....I want to drive my Geo metro, it never breaks, but it can't tow anything. LOL!

Click to expand...

make sure they dynamically balance the new one piece. Love mine.