Ok my 01 LS 4x4 Blazer has some issues and I cannot afford to take it to anybody else. I can most likely fix the issue myself, if I can just figure out what it is. So I noticed my truck would vibrate as I let off the gas at highway speeds. This got worse over about a week or so, to the point of it starting to vibrate slowly as the truck started moving and then more violently as I would get up to 40ish. Wheel, dash, seats, floorboard, and everything else. I saw that the seal on the diff where the CV goes in had play, so I took the axle out. My front driveshaft is now out too. I noticed the female shaft that the axle end goes into (inside of the diff) will still rotate with the wheels rolling. I know the back wheels aren't causing it to spin beacause the front drive shaft is out. My question is, if I remove the other CV joint on the passenger side will it cause the diff to quit spinning? I took the axle apart once I had it out and put the most outlerlying section of it back in so it would hold the bearing hub together inside the spindle. Im guessing the reason for the vibration is the female axle inside of the diff is rotating and bouncing around because it has play. Since the shaft that goes into it and the seal that holds it all even and centered is now gone. When I look in the hole (before sealing and covering it) I can see it laying loosely on the bottom of it's housing. If I stick my finger in I can move it up or down and it has circular play. Can I bypass my diff and leave it "unhooked" as I drive? I don't need 4x4 for now until I can afford all the parts that were broke when I bought it. I just need to be able to get to work. This has caused my tie rod ends to come loose and also my upper ball joints. I rotated my tires from front to back and side to side to see if it was the tires. Vibration still in the front. Ball joints, control arms, tie rods, and bearings are all tight and working properly. The only other possibility I can think of is an alignment. I couldn't imagine the drive shaft is bent. It wouldn't have progressed like it did, or as fast as it did. Especially since the ujoints are fine and working properly. What is the best way to check my tire alignment at home to get it as close as possible? I can't drive it until I figure out this vibration. Thanks in advance.

 

So let me get this straight... You've pulled both front CV shafts (reinstalling the outer most section of each into the hub/bearing assemblies) as well as the front driveshaft? And the problem still persists. If so and if the vibration is definitely coming from the front end (felt in the steering wheel), then you have something amiss with those parts that are still installed and rotating in the front end. I doubt very much that an alignment will affect anything to this degree unless things are WAY out of whack. If all of the front end parts check out and moving the wheels doesn't alter the feeling, I'm at a loss for what could cause it. It sounds like you have covered the bases, but yet the problem still persists.

If you haven't removed both inner CV shafts and still have one installed, which it sounds like you do...that isn't very good for the front diff.

Are you sure that the vibration is felt from the front end? The rear driveshaft attaches to the transfer case right around the back of the driver seat. I had a farm truck (2004 2500HD 6.0L) that was chewing through slip yoke bushings in the tailhousing of the transfer case. This was a result of an issue in the transfer case with fluid flowing into the tail housing resulting in a dry bushing. Ended up replacing the driveshaft and the transfer case to solve the problem once and for all. When the bushing would go out, it would feel like the entire truck was coming apart.

It is possible that you had a problem with the front axle engagement mechanism (what the vacuum actuator engages to connect the passenger side output to the front differential to engage the front axle). If this were partially engaged, it would make quite a racket. I'm not sure I have ever experienced a violent vibration as a result of it, but it's difficult to tell from your description so I'm just covering some bases on what you could look into. There is a DIY thread in the Tech Article section that covers the front axle engagement.

BTW, please do not post the same thread multiple times across multiple forum sections; rule #4 and all. I have removed the two other threads you have created. If you wish to have this thread moved to a different forum section, please PM a member of the staff and we'll get that taken care of for you. Thanks!

 

Ok so first of all, thanx for the reply and help and sorry about the double posting. Ok so I DO still have my pass side cv still in. I plan to remove it shortly today. As far as the axle engagement, I have removed the cable that runs from the vaccum, and also my encoder motor from the tcase. I thought at first my front end was partially engaged..so i manually clicked it into 2wd. Once i remove the other cv axle, it should bypass and disengage the diff from moving internally at all?

 

Yeah, it really should be an all or nothing thing with the front axle shafts. You shouldn't remove one and leave the other installed.

As far as the front axle engagement is concerned, just disconnecting the cable from the actuator or the vacuum lines from the transfer case and/or actuator does not rule out a partially engaged front axle. Many times over the years, I have seen a gummed up or frozen cable be the culprit for partial front end engagement.

 

It really sounds more like a tire issue than anything to do with the front differential. Have you tried rotating the tires front to rear?