factory Viscous LSD going bad?

[Brettt]

So after trying a multitude of things to stop our vibration, it is still hanging around. We have replaced both axles, hub bearings, played with ride height and even checked to make sure the frame and strut towers were good and square. The vibration isn't as bad as it was at its worst, but it is still there. The Nissan mechanic across town said to take a look at the lsd. I guess it makes sense considering we've replaced everything else drivetrain-related.

The question I pose to you guys is this: have you ever heard of a factory viscous unit causing a vibration only when you turn one way? Ours happens when we turn right and only when we turn right. Not sure really what else to do. We've got some diff-quieting stuff to put in the transmission for this weekend, but I don't understand enough about the viscous unit to really know if it will make a difference. After I get done with classes tomorrow its down to the shop to drain the fluid and try out some redline heavy shockproof gear oil. Past that, I suppose we start pulling the transmission...

Thanks guys

[Greg Amy]

...have you ever heard of a factory viscous unit causing a vibration only when you turn one way?

Nope. But they don't last long as "LSD" in racing conditions.

We've got some diff-quieting stuff to put in the transmission for this weekend

Won't do anything. The diff is a sealed unit, with the viscous fluid completely contained inside another internal container. Save your money.

Does the frequency of the vibration correlate to speed? Are you absolutely sure it's not a wheel/tire? When you replaced all those parts, were they with new stuff?

GA

[Brettt]

Both of the axles are new units. We had tried remans in the past, but got new ones this time in an attempt to rule things out. The only part we haven't put on the car is new outer hubs, but the hubs on the car don't really look bad. The bearings didn't look bad themselves, but I plan on replacing them tomorrow since we have 2 sitting in my tool box.

The frequency of the vibration seems to correlate with speed, but the intensity seems to remain more or less constant with angle on the steering. If you give the car more steering input, the intensity of vibration ramps up quite a bit with the left side loaded in a corner.

Same as before, however, it's smooth turning left. Even with the ride height just shy of 7" we still have only maybe 1/4" of lee-way in our left half-shaft when I take the nut loose before it bottoms out. Like I said before, we measured the lower control arm mounting points and they're within a silly millimeter of factory specs.

The only thing that I can think of is Topeka only has 5 right hand corners... so we can take some camber out of that wheel and hopefully give us a little more room there. We're running out of ideas...

Another racer here told me "Just run it until something breaks. Then you'll know what was wrong." As much as I hate that idea, it is starting to sound pretty good...

[Greg Amy]

I'm not clear: did you, or did you not, replace front wheel bearings with new? Sounds like a bad LF wheel bearing.

[Brettt]

As far as the wheel/tire situation, I've had two different kinds of wheels and 3 different types of tires up there. None of it seemed to make a difference regarding the vibration.

[Brettt]

We had replaced the wheel bearing towards the end of last season, but not since we have changed the rest of the driveline components. The races looked good when we pulled the hub out and none of the balls were scarred up, so we assumed that wasn't the problem.

-Yes it was a new bearing we put in. Watching the video from the race verified that it was shaking so bad the dash was trying to hop around. Could a wheel bearing cause that violent of a shake? It's much more of a hammering than a buzzing or grinding vibration, if that helps. Almost like you picked up a bunch of snow or something in your wheel to throw it out of whack, but the wheels are all balanced to zeroes- I did it myself.

[Matt93SE]

Stupid Q, but you don't have a tire rubbing against the strut or wheel well or something do you?

I would figure with that much interference it should be obvious if you have wheel or tire rubbing, but it's at least work asking.