Progressive front differential failure?
 

Several months ago I posted about an instance of steering shudder in my teal SVX; a left-right twitch through the steering wheel that made me think either front tire was going down or the power steering was leaking/failing. I pulled over, found nothing visibly amiss, and continued on to my destination without a problem. Subsequently put the car into the shop for a check of the front end, along with tire balancing and rotation. They declared the car healthy, and I've been driving it 2-4 times per week, about 25 miles per day, without incident, until last week.

A related aside (or not): Several times last winter/spring I noticed a clacking/rattling sound upon making a hard left-hand turn from a stop; sounded like it was coming from directly behind the instrument cluster. Not the clunk of a failing CV joint (with which I'm familiar), but more of a rapid clack-clack-clack. I poked around underneath the car and in the engine bay for something loose that could be rattling, maybe road debris hung-up in the suspension, and checked the front diff level. The noise didn't persist, the car drove fine, and I kept driving, drawing no connection between this noise and the steering shudder. (I don't recall which came first.) Could be totally unrelated.

Last week I got the shudder again, so noticeable I felt sure the right front tire was going down. Nope. Jacked-up each front corner, gave the tires a tug and felt very slight left-right play, and a corresponding, faint clunk. Lug nuts tight. No apparent tire defect. (Not that I'm some expert; I just hoped to find something obviously wrong.) Drove it to work and heard that clacking sound again when turning (right, this time) off a side street onto the main drag. No shudder in the wheel, no noise after that, 12 miles to town. Back to the shop, my mechanic confirmed very slight play in the rack (the alignment guy thought it acceptable), but reported nothing else wrong he could find.

(If you've read this far) my question is, are these symptoms consistent with a front differential that's up to no good? I think of the diff as something that would just go BANG, but I really know nothing about the inner workings of the thing. (And admittedly, I'm a little paranoid about front diff failure.) Is there any way to diagnose this aside from metal bits in the diff lube? I'm at a loss, and hate to just keep driving the thing 'til something lets go. Seeking words of wisdom from you guys with experience.

Thanks,
dcb

Re: Progressive front differential failure?
 

From what I gather, it sounds like your saying during turning your experiencing binding. A quick easy diagnosis would be to install the FWD fuse, then try to reproduce the symptom.

Re: Progressive front differential failure?
 

No, definitely not binding, but an intermittent shimmy in the steering, plus an occasional clacking noise on turning. Definitely something rotational in the front end. I'm leaning toward a CV joint, though I don't know why the chatter wouldn't be constant.

dcb

Re: Progressive front differential failure?
 

It may be the front differential gears that have a tooth problem. Jack up the front end, with it in park, rotate one wheel so that the other wheel rotates in the opposite direction. You will be able to feel the sun and planet gears meshing, if it has a tooth damaged you will feel it.

Harvey.

My front diff showed no signs of wear before it went, except for one very soft shudder that vibrated through the shifter that I just happened to be holding, when I went over a speed bump at about 5mph.
The next time I hit the gas, clunkclunkclunk, it was done.

Keep in mind my trans was very much abused.

Re: Progressive front differential failure?
 

I can only imagine in general that speed bumps are the devil for AWD cars?
Every time I bounce over one I cringe....

I don't think they are any more a devil than a simple icy road, or any other road hazard.

Re: Progressive front differential failure?
 

I had a similar problem with an Impreza. I fixed it by tightening the side plates on the differential a little. Those side plates hold the bearings to the race in the front diff.

Re: Progressive front differential failure?
 

Upon review: CV joint. (Apparently.)

dcb

Re: Progressive front differential failure?
 

i hav the same problem....cv joint and cracked diff:/