Vibration Under Acceleration

Greetings,

I'm a new member of this forum but I've been reading it, whenever a problem with my car crops up, for the last few years. Thanks to all for the solutions I've found.

My car is a 95 Aurora and although I do love it, I have had quite a few problems. Presently, I have severe vibration of the front end under acceleration, but only within the range of approximately 2400 to 2600 rpm. It is not sensitive to the speed of the car itself. I have had it happen at 40 mph in the city and at 80 mph on the highway. It really only seems to depend on load, hence the rpm range.

I have read all other threads in this forum pretaining to front end vibration. They all either; have to do with wheel balancing and alignment or they never came to a solution for the problem. I do not believe my particular problem is related to wheel balancing or alignment because the vibration ceases immediately upon removal of power.

I know this can be a symptom of cv joint failure, but I do not consistantly hear popping or grinding when turning. I have not inspected the cv boots for damage. I do occasionally have lurching when putting the car in reverse after starting the engine. So I suppose it could be engine/transmission mounts.

I have made an attempt to be as specific as possible, and I HAVE read all the other threads I can find on vibration. I appreciate any thoughtful responses.


Thanks

I had the same thing happen on my 2000 Impala. It was my CV shaft. I never heard noice when turning or anything but when I put it up on the hoist at a shop the shaft wobbled on acceleration.

I did find the solution to my vibration and it was the inner cv joint on the passenger's side half shaft. I replaced them myself, along with front lower ball joints, tie rod ends and sway bar mounting links.

It seems to me that almost no one actually takes to the time to describe how they fixed whatever problem they had if they did do it themselves. If you are a do-it-yourselfer like myself, you may find this decidedly inconvenient. For anyone thinking they may need to tackle the above task, I have taken the time to write out the entire procedure with as much detail as I deem necessary (or as much as I can remember in some cases). I recommend getting a couple buddies that know how to use a wrench at least to help you out. I did and it saved me a ton of time, beer helps too (although the productivity may suffer slightly). The basic procedure went as follows:

The first thing to do is go to your local auto parts store (we used autozone) and buy/rent a few tools you may not have. These include a slide hammer, WITH the half-shaft removal tool J-28468 or J-33008. My local autozone did not have the J-28468 or J-33008 which cost us about 3 hours during the job. Also, the hub removal tool J-28733 is useful for pulling the hub and wheel bearing assembly off, although we used my pulley puller. I would also HIGHLY recommend having an impact gun on hand to break things like the spindle nut loose. You will need a 33mm socket for that. You will also need a ball joint removal tool, although the "pickle fork" they gave us at autozone destroyed the boots, so if you don't plan on replacing all the joints like I did, you should use a block of wood and a hammer and just wail on the stud until they unseat (not easy unless the car is on a lift I suppose). You will also need a pretty sizable (size T55) socket driven torx bit. Don't skimp on quality on these because if you put lots of torque through the cheap ones they will explode (especially if you will be using an impact gun).

Obviously you will need a good jack and some jack-stands. Break the wheel nuts loose before you raise the car or you will have to have someone hit the brakes while you do it. Pull the front wheels off after blocking the rear wheels, raising the car, positioning the jack stands and removing the wheel lugs. I found the best place for the jack stands to be the big chassis cross-member just aft of the radiator.
The next thing to do is take a good long look at how everything goes together, take note of the number of exposed threads on all fasteners you plan on removing (it should be fairly obvious which ones those will be) also mark the positions of the tie rod ends. If you end up replacing these it is useful to know where they were so you can steer as far as the nearest alignment shop at the end of the job.

We found it best to remove the brake calipers and rotors so you can see what you are doing and to open up the work area. You'll need a large allen key to remove the 2 caliper mount bolts (I don't remember the size). It will likely require the use of a hammer to break them loose initially as they are located inboard of the brake rotor on either side of the caliper (no space to use a breaker bar or impact gun in here!). Find something to support the calipers after you have probably had to pry them off with a big screw driver or similar. Don't damage the brake lines or you will add a few hours to the job.

The next thing we did was pull the bearing hubs off. Before we could do this however, we needed to remove the spindle nut. Place a drift or screwdriver across two of the wheel studs and go to town with an impact gun. If you don't have an impact gun, well, good luck. Maybe try not removing the brakes first, then have a buddy lay hard on the brakes while you do work with a big socket wrench and breaker bar. Now you are ready to remove the hub assembly. This is where the torx bits and impact gun come in handy. There is one hole in the hub face large enough to back the bolts out of so you have to spin the hub around as you take each bolt out. Use the puller you rented as the instructions dictate, or do like we did and use your own big two-jaw puller to grip the face of the hub in the two jaw cut-outs. We used a slide hammer to pull the whole thing out. There is a metal plate that protects the half shaft and associated from the brake rotor's heat. Just pull it off but DON'T forget to put it back on when you put it all back together, it is essential even if it does't look like it. Once the hub is loose, unplug the wheel speed sensor and put the plug in an out-of-the-way place. You will need to unclip this plug from the metal plate, a screwdriver should do the trick.

You should now remove the sway bar links. They consist of a single bolt running through a series of rubber bushings, steel washers and a spacer. This link holds the sway bar into the lower control arm. Hold the nut and spin the bolt head or vice-versa (we used an impact gun for this operation, it caused the bolt to literally disintegrate because it was so rusted through). You may need to shake/compress the lower control arm and sway bar to get the bolts to slide out.

The next task is to remove the lower ball joint. The stud is located just beneath the outer cv joint. Remove the cotter pin and take the nut off of the stud. This is where things get tricky. There is no space to swing a hammer even if the cv joint were not there. You really need a ball joint remover. Get ready to either destroy your joint boots or use a compressive ball joint remover. We used the pickle fork by wedging it in between the joint and the bottom of the knuckle and wailing on it with a hammer. They'll pop loose eventually, and if they don't, keep wailing on them (we tore the boots on both sides doing this but they did have 120k miles on them). You can help the process along by hammering "lightly" on either side of the joint and knuckle to loosen things up.
Once the ball joints have come free, pry the stud out of the knuckle and let the lower control arm hang freely. Next, remove the cotter pin from the sutd and remove the nut. This one you may be able to remove with a hammer and block of wood, but if not, use the pickle fork like you did with the ball joint.

Note: If you plan on replacing the tie rod end. Take note of the position of the rod end on the tie rod. Loosen the lock nut and mark the end of the joint. Remove the joint by holding the tie rod at the squared off portion and spinning the joint off at its squared off portion.

The entire strut should now be free to move around its "pivot" at the top. Use this freedom to slip the outer end of the half shaft out of the knuckle. This is where that special tool for the slide hammer comes in. By its shape, if you have it, its use should be straight forward. Put the "c-joint" around the half shaft right at the interface of the transmission and the inner cv joint. Start wailing on it until the whole shaft slides out of the transmission. Lower the shaft out of the car. It's not a really smooth removal and you have to dance around the knuckle and sway bar but it will come out. The thing to remember about using tool J-28468 or J-33008 is that some shafts will pull out by hand with a little jiggling and some won't. It just depends on your car. For us, the passenger's side shaft came out by hand after a few taps with a hammer and screw driver (there is a groove on the inner joint housing that is made for a flat head screw driver to sit in) while I jiggled it around to prevent it binding up. The driver's side however is located right above a major chassis cross member so there is almost no room to work and we spent at least 2 hours with screwdrivers, pry bars and hammers trying to free the shaft from the transmission. After all that time and damage to the transmission housing, we finally had to break down and make a tool to use. I did it by cutting some steel plates and welding them into a "c-like" profile. I then drilled a hole in the end to bolt the slidehammer into. It was a long shot but it worked. I would recommend just making sure you have the tool and saving yourself the time.

The new shafts should look just like the old ones. They should fit on either side. One thing to do once you have the old shafts out is to wiggle and move each joint around to see if you can hear or feel which one is bad. For us, it was very clear that the inner joint on one of the shafts was almost completely destroyed. The ball bearings inside were most likely barely contained by the inner cage and the play was audible through the boot. This at least confirmed that we weren't wasting our time.
Seating the new shafts should be a simple matter of inserting them into the transmission. Be sure to grease the inner splines on all shafts to facilitate ease of installation. Seat the shafts by tapping on them with a hammer and screwdriver in the groove on the inner joint housings. This is a good trick for the one on the driver's side. All I can really say is that you just need to be sure that NO splines are showing once you have re-assembled everything. However you do that is up to you. By this point in the job, you are familiar enough with everything that you should know where things go and how it should look.

Putting everything back together is just the reverse of the above. I know that sounds simplistic but that really is all it takes. Make sure to use the new spindle nut that should have been provided with your new half shafts (typically they are threaded onto the ends of the new shafts). Also, make sure you inspect all boots and joints. If something looks like its bad, the time to replace it is now, not after it breaks on the highway and you swap out at 70 mph. Also, grease EVERYTHING before you put the fasteners back on. It just makes everything easier and it is better for all those linkages and bearings and bushings under there. Impact everything on that you can. The bottom line is that bolts and studs are made to only ever be in tension, NOT bending. If things are not tight enough, studs and bolts will fatigue and break from the vibrations and movement of the suspension.

That is really all I can offer. I hope it helps someone else save some money. I can't imagine that I saved less than $2,000 doing this myself. I bought the parts from autozone and RockAuto.com. Rock Auto has excellent prices. I had both shafts (new) next-day shipped to my door for around $145 with no core. Autozone wanted me to wait 5 days to get it to thier store and they wanted $160 before core for remanufactured ones from the same company (Cardone). Rock Auto also has almost every available part for almost every car out there (In the states).