intermittent rear vibration at 60mph

I've done my share of research on here for my current issue. But, before I move forward I'm just gonna throw my symptoms out here for anyone who will comment as i could really use some help with this.
At approx 60mph and upward I get a loud intermittent vibration and sound from the rear. It goes away upon deceleration. It sounds very much like driving over the vibration strips on the edges of highway lanes to keep you on the road.But it feels like the growl of a bearing. So I believe I've narrowed it down to a rear bearing or differential problem. It absolutely has a bad bearing feel but it feels like its coming from the center of the rear.
I've checked the tires and rims, the wheel weights are intact, my ujoints are solid my driveshaft hasn't thrown a weight. I do not want to start with things that it obviously isn't-such as rebalancing, alignments etc. I have about 80,000 miles and had the rear diff fluid done at around 60,000 with correct fluid.
What do I tell the shop to fix/replace and any guesses on cost?
Please help.

I'm not opposed to crackin' open that rear pumpkin' and seeing what the fluid looks like smells like and do whatever, perhaps i caught it early enough to change the fluid and limp her along another 25,000 miles?
I didn't personally do the fluid either, I had a oil change place do all my fluid after I bought it with 55k on it. I specifically told them about the LSD-5 or whatever and I even had them call an Isuzu dealership to verify they were using the right stuff. I was very much a newb back then but I did insist that.

Yes, check your rear diff fluid (both level & for metal shavings). It may be as simple as low level.

Remember though that gear oil smells pretty bad even when new. Don't mistake that smell for burnt fluid.

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Originally Posted by tom4bren

Yes, check your rear diff fluid (both level & for metal shavings). It may be as simple as low level.

Remember though that gear oil smells pretty bad even when new. Don't mistake that smell for burnt fluid.

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If it doesn't "leak out" (i haven't ever seen any leaks ) could it still be low?

Yah, you can usually spot leaks ... but not always. If the leak is out by the wheel, the oil may get blown away before you'd notice. Murphy's law does apply to the VX.

Remember a sage piece of advice though: ALWAYS remove the fill plug first, NEVER the drain plug first - just in case you can't get the fill plug out. Ya can't drive with an empty differential. IIRC, credit goes to etlsport for that one.

If you are lifted too high, you will get that grinding. I was using OME 919s plus DAYSTAR spacers and it was really bad. Removed the spacers and it was manageable by greasing the driveshaft. Try greasing first. It helps. :yesgray:

i had to have a rear wheel bearing replaced but the noise didnt start at 60mph it was basically always there

I lifted with Old Man Emu 912's 4 yrs. ago and haven't had an issue besides the general whine on acceleration at freeway speeds and a very light grumble on decel. This is a different & more noisy/feely thing...but tonite (when i get outa work) I'll start with greasing the driveshaft and I'll check the rear diff fluid out. I wish I had off today! Thanks for the help folks:thumbup:

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Originally Posted by SilverBullet75

Try greasing first. It helps. :yesgray:

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+1, I was getting a grinding noise from the driveshaft u joints until I started greasing them regularly. I would only get the vibration/noise at highway speed, so it seems to fit the problem.

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Originally Posted by evillecutter

i had to have a rear wheel bearing replaced but the noise didnt start at 60mph it was basically always there

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There is no such thing as rear wheel bearings,front ones but not rear ones:_confused

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Originally Posted by WILLY

There is no such thing as rear wheel bearings,front ones but not rear ones:_confused

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autozone and my rear wheels say differently:

http://www.autozone.com/autozone/par...Rear/_/N-ah8dj

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Originally Posted by WILLY

There is no such thing as rear wheel bearings,front ones but not rear ones:_confused

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Isuzu warranty paid for my rear wheel bearings to be replaced. I guess they didn't know the VX didn't have any.

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Originally Posted by SilverBullet75

...greasing the driveshaft. Try greasing first. It helps. :yesgray:

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X2

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Originally Posted by evillecutter

i had to have a rear wheel bearing replaced but the noise didnt start at 60mph it was basically always there

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Evil:evil:cutter, was it a bearing by the wheel hub or something in the center of the axel if you recall? Do you remember what it cost?

i dunno i had the work done when i had just bought it and the guy (only mechanic trust) said it needed a new bearing (he pointed to the drivers side rear wheel) and that's why it was loud - i cannot find the receipt but i think it was about $450 parts and labor for the bearing, all the rotors to be turned,all new front pads, and one new front caliper - sorry prob doesnt help much if i see him soon ill ask

The rear wheel bearings are normally called the "rear axle bearings".
They are installed on the outer end of the axle.
To replace, remove wheel, brake caliper, disc etc.
Pull axle out and then you need at least a 5 ton press to press the old bearing off, and the new one on.

But from the description it sounds like greasing the driveshaft will fix the problem. Remember there are 3 nipples, and all need to be greased.
2 x u joints and the splined yoke at the gearbox end of the shaft.

Rear axle bearing noise is very easy to distinguish from other noises.
It makes a "whup-----whup------whup" sound that corresponds to one turn of the wheel.

PK

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Originally Posted by evillecutter

i dunno i had the work done when i had just bought it and the guy (only mechanic trust) said it needed a new bearing (he pointed to the drivers side rear wheel) and that's why it was loud - i cannot find the receipt but i think it was about $450 parts and labor for the bearing, all the rotors to be turned,all new front pads, and one new front caliper - sorry prob doesnt help much if i see him soon ill ask

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Thanks Evil:winkgray:

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Originally Posted by PK

The rear wheel bearings are normally called the "rear axle bearings".
They are installed on the outer end of the axle.
To replace, remove wheel, brake caliper, disc etc.
Pull axle out and then you need at least a 5 ton press to press the old bearing off, and the new one on.

But from the description it sounds like greasing the driveshaft will fix the problem. Remember there are 3 nipples, and all need to be greased.
2 x u joints and the splined yoke at the gearbox end of the shaft.

Rear axle bearing noise is very easy to distinguish from other noises.
It makes a "whup-----whup------whup" sound that corresponds to one turn of the wheel.

PK

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I like your knowledge. Tonite I checked rear diff fluid, it smells just fine and is up to level, and it has a great oily feel, looks like new actually. So I greased up my drive shaft at all 3 points and will check it out tomoro. Thanks PK and everyone else who took the time to respond. :thanx:

So far I haven't got her out on the highway so no updates. but once again thanx so far for all the tips and suggestions. Vehicross.info is still the undisputed Best Forum Site in the World.

Follow up report--Greasing the driveshaft has fixed the odd vibration. I cant believe it. However, there is still a high pitched howl from the rear at the speeds stated earlier. Thanks to all who responded and I hope this will help someone else in the future.