What would cause this vibration

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davem3261

New member
I got a vibration between 65-80 on the highway. There is no vibration while I'm coasting. Slight vibration under load. It most noticeable when I'm barely on the throttle, not accelerating or coasting. I removed the front driveshaft, no change. I just installed a new 5" aluminum driveshaft expecting that to fix it. Didn't help.

I tried putting the axles on jack stands and removed the rear tires. Brought it up to speed (lug nuts on rotors) and I can still feel it. It's just really annoying that every time I lift the throttle on the highway I can feel the vibration. It's defiantly a high speed vibe. Not like a tire out of balance. I don't know what else to look at
 
Put it on stands again and be ready to yank the axles this time. Depending on miles you could have rear diff looseness that will cause this.
 
Billysgoat said:
Put it on stands again and be ready to yank the axles this time. Depending on miles you could have rear diff looseness that will cause this.
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The rear was rebuilt for a grinding noise at 55k under warranty. Truck has 77k now. I'm assuming they changed gears and bearings.

It does have a clunk when I let off the throttle or get back into it. I will pull the axles tonite and see what that does. Are you suggesting bad bearings, bad carrier, or too much backlash?
 
davem3261 said:
The rear was rebuilt for a grinding noise at 55k under warranty. Truck has 77k now. I'm assuming they changed gears and bearings.

It does have a clunk when I let off the throttle or get back into it. I will pull the axles tonite and see what that does. Are you suggesting bad bearings, bad carrier, or too much backlash?
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I just put a locker in mine and it now clunks pretty good which is normal for a locker, before that it did not clunk at all. This sounds like what happened on my 2cnd gen when the bearings wore into the side of the housing allowing the ring gear to move under load. If they rebuilt it and did not get enough preload on the bearings it would be about right mileage wise to start doing this.

Truck on stands, remove tires, run and check, remove axle shafts, run and check. If the vibration is still present drop the diff cover and run it a bit, maybe take a pry bar and see if you can move the ring gear in the case. Backlash is .005-.007, more than that means the bearings are worn allowing the carrier to move around. When I say run it a bit, I do mean just a bit! Best to have a helper run the truck while you watch the diff, it should not move in anything but a circular motion. Oh, and don't forget to shift it to neutral and allow to spin down before finding park.

Hope this helps.
 
I will give that a shot this weekend and see how it looks. The only other thing I can think of is the transmission mount. It appears fine, no splits. I can grab the transfer case and move it about a quarter inch up and down. The rubber is soft and it is original . I'm thinking it could be changing the driveline angles under load.
 
.007 backlash. Gears look fine. I don't have the proper torque wrench for rotational torque. I have a snap on 1/4 digital torque wrench and it wouldn't read the minumum torque when I was spinning it. It seems like it turns easily. One thing I did notice is that it takes some force to get the carrier spinning. Once it's going it spins easily.


With the axles out. Transfer case in neutral. I can hear bearing noise in the rear end while spinning the driveshaft by hand. No noise at all in the transfer case. Should the rear end be silent? I can't move the pinion in and out or up and down. Seems solid. I'm going to order a new set of bearings for the rear and change them out and see what happens. Unless someone convinces me not to.
 
Trans mount will do it at times, not being there to see how bad the vibration is makes it kinda hard to diagnose. The rear should be pretty quiet, even before new bearings mine was silent. If you replace the rear bearings, it is pretty easy if you only do the carrier units, with the pinion thrown into the mix? Get a big cheater pipe, and I mean a BIG cheater pipe, and a torque beam wrench, makes life much easier.

If you are getting bearing noise from the rear end something is wonky, I am pretty sure the rear diff on mine was shot, but it was still quiet as a mouse. Noise tells me something is not right and if you do not take the time required to do it right? Ya' got issues man! Change the trans mount first, much cheaper and easier, the rear end can wait till you have a full weekend to fool with it. If you replace the pinion as well, just get the master kit from east coast gear supply, they sell a Yukon kit that is very reasonable and it comes with two crush sleeves. You will need two, it is so easy to screw one up and you do not have to pull the pinion seal to replace them.
 
I will report back when I get new bearings in it. I read through a number of unsolved vibration threads and I'm not giving up yet.
 
tranny shouldn't move (vibrate) with the rear end on jacks.. there is no load

are the axle tubes or axle bars bent? is the locker going out?
 
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307diesel said:
Every truck I've bern in that has a 48re has this vibration. I'm curious myself.
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i dropped my 2 piece DS for a mega cab shaft a few years ago. it was one of the best "non power adders" ive ever done. i hated that feeling.
 
I have the same similar issue as described, haven't looked at it any further.

New u joints (drive shaft and axle), rebuilt transfer-case, different tires and rims, swapped transmission..
 
Might lay under the truck, and have someone rock it really hard back and forth in Park. If something is loose or clunking you may find it that way. That's how I found out every one of my ubolts had stretched in 2 different trucks.
 
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