There's two half shafts. Most often the inner cv joint on the right one causes the problem.
First, jack the right front wheel off the ground. Remove the cotter pin, lock washer, anti-rattle washer, and axle nut. Never remove that axle nut with the weight of the vehicle on the tire. Doing so will instantly cause a noisy wheel bearing. That bearing is held together by the outer cv joint and nut.
With the axle nut removed, use your thumb to push the shaft towards the center of the van. It should push rather hard and pop right back out when you release pressure. If it does not, the internal spring is broken. That will allow the inner cv joint housing to walk out of the transmission and wobble. The dealership parts department has new springs with cups on the end for about four bucks.
Next, the inner joint housing must be inspected. That requires removal of the half shaft and disassembly of the inner joint and boot. Clean out all the grease, then run your finger over the six polished surfaces that the three large rollers run on. If you can feel any slight irregularity, you REALLY have junk. If they feel smooth to the touch, wipe them perfectly clean, then shine a light in there and look at the reflection. Any sign of waviness, similar to looking at a car body reflecting the ground at a car show, is cause for replacement. Under acceleration, the rollers bind on the worn spots and refuse to roll in and out as the shaft turns. The failure of the shaft to freely change its length causes it to push on the spindle and lower control arm. That tugs on the steering linkage causing what you're feeling.
Replacement housings are very expensive from the dealer. You're better off buying a quality remanufactured half shaft but you should be aware that they usually just clean them up and install new boots. They don't always inspect the housings for this problem because it occurs much less often than a simple torn boot. Even if you just replaced the right shaft, inspect it first. I ran into more than a dozen of these one summer, and the left inner joint was the culprit on only one of them.
Another possible cause of shaking is a front brake caliper that doesn't fully release. To check for this, you can stop on a slight incline, put the transmission in neutral, then see if the van starts to roll when you release the brake. If the van won't move, you likely have a brake issue which is not always serious. Try to notice if the wobble is most noticeable shortly after applying the brakes, and if it goes away after driving on the highway for a while. Holler back if you think the brakes are the problem.
Saturday, December 12th, 2009 AT 12:25 PM