Not a good night... Took my daughter and friends into town tonight so they could go bowling-in the process I had to hammer the gas a little to avoid an accident. After I dropped them off, I took off for home and when I hit about 45 mph, I started getting a vibration from the rear end. At first I thought I might have picked up a nail and was losing tire pressure-pulled over, nothing. Started going again...sure enough, the shake came back. No vibration in the front, no shake in the steering wheel...just in the rear. The tires have less than 500 miles on them and I know they were balanced out right. (I work in a tire shop and did them myself) I have a slight leak around the differential where the driveshaft comes in, so I need to check the fluid level. I'm also going to put the wheels on the balancer tomorrow at work to make sure I didn't throw a weight. (though this seems like more vibration than a thrown weight would produce)

Any ideas? This is the worst timing because I just bought this thing and have a payment due soon. Plus we just spent all our money on x-mas for the kids. Urg.

 

Have you thought about U-joints, could also be what is causing the seal to fail by deforming the rubber gasket..

 

well, I just went outside and looked the driveshaft u joints over. (geez it's cold out tonight!) Everything appears to look all right and there's no play in the driveshaft. Another quick question-if it is low on fluid can I top it off with some Penzoil Synthetic 75w-90 GL-5 that I have leftover from my Grand Cherokee diffs?

 

I'm not going to say it is ok since we don't know if the diff has posi or maybe limited slip....sometimes these special differentials require special fluids. I would stick with dino style until you get the leak fixed and then find out if it will work with the hardware inside...

 

You should be ok to top off your diff with what you have.





Differential, Standard, Front Drive Axle, Rear Axle

Axle Lubricant (GMP/N89021671) or SAE 80W-90 GL-5 Gear Lubricant.


Differential, Locking

Axle Lubricant (GMP/N1052271) or SAE 80W-90 GL-5 Gear Lubricant. Do not add friction modifier
Good idea to start with re-checking the wheel balance. As you work in a tire shop, you can probably run the truck in gear on the hoist and see if you can pinpoint the area of vibration, in by the diff or out at the end of the axle....possible bearings.
Re-check the u-joints while you have it in the air.

 

i threw a weight on my rangers left rear tire.... shook hard enough to break traction at 55mph..... of course it was on studded snow tires on the highway........ sent me sideways... scary stuff...lol

 

Wow...now I'm going to ask the stupid question of the night....how do I figure out if it is? There's no tag on the rear diff cover like there was on my Jeep. (I know I'm going to kick myself when somebody answers this) I admit it, my rear end experience and knowledge is VERY limited.

 

The Glove box should have a tag inside with all your truck's code's, Paint, Rear diff.

 

ok, so the next morning I took my Blazer into work...no vibration in the rear end. Seems to be a little noise from back there, but I might be listening too hard to nothing. Checked the balance on the tires, only off 0.25 ounces on one tire...definitely not enough to cause any trouble. While I had it up on the lift, I rechecked the drive shaft-no play in it. When I spun on of the tires, the other spun in the opposite direction-limited slip? (like I said, I'm pretty stupid on rear ends) Fired it up and put it in drive while on the lift (which worried the hell out a few in the shop!)...while only one wheel spun (I think my brakes are dragging on the driver's rear...not sure what is causing it though), I couldn't pick up any vibrations from the diff.Also checked the diff lube...full. Urgh...I hate diagnosing phantom stuff...

 

did you do the rock back and forth on the ground? this will tell you if you have an axle bearing going out. If you have a brake dragging that might cause some vib. but not a lot as you had posted, not unless it was starting to lock up.

Brake drag can be caused by bad wheel cyclender. Try changing it out. While you had your tires off did you inspect the drums? Or do you have all wheel disk? Disk could be a warped rotor.