Limited Slip Rear "clunk"

[Gus Gorilla]

I noticed this great noise from my rear diff yesterday. While parked, if the truck is pushed or rocked side to side the rear axle shifts in and out. Not a lot, but it's enough that it makes this disturbing clunk noise. The axle is a Limited Slip 4.10 in my 01 ST with about 107K miles. I was inside it about November around 90K miles changing the fluid. No problems found. The bad part is that I don't know if it always did this, if it's normal, if it's broke, or if I'm just paranoid. Aside from the above, there is no concern. No noise, vibration, or harshness. So school me Forum, what do I have here. I'm going out to jack it up to try to measure this play and further inspect. :scratch:

 

[nooberiffic]

torched a clutch pack in the LSD?

 

[Gus Gorilla]

Possible, I don't drive it hard though. No offroading, no racing. After checking it out it is maybe 3/32 to 1/8 of an inch movement, straight in and out. No up down, no top to bottom, no front to rear movement. And it is identical on both sides. I did find signs of a leaking seal on the drivers side. Not too bad, just some dirt stuck in it. Looks like a slow leak. I raised one wheel, dropped it in Neutral and tried to turn it with the other on the ground and couldn't. So the clutches are holding. Now what, is it possible this is normal and I just never noticed it before?

 

[junkYARDbuilt]

I was thinking wheel bearing untill you said no up and down movement. Perhaps a little exploratory surgery is in order. I dont THINK it should move in and out, but I'm no axle guru.

 

[nooberiffic]

Hmmm. I dont know and I am no expert, but it sounds like something has happened inside the carrier. The spidergears and side gears go in, then the LS clutch pack is put in. the Clutch pack is pushing up against the gears and the c clip stopping movement in (thats how you take the c clip out). So, if you are getting in and out movement on the axle shaft, then something might have happened to the gears or the clutch pack.

 

[Gus Gorilla]

Ok, so the spring is holding the side gears tight against the clutch packs. The axle C clip stops outward travel, is held in the side gear and can't move inward to come off due to the pinion shaft. As the clutch packs wear, they will get thinner. The question here is, Will the clutch packs become thin enough for the side gears to move outward allowing play? or possibly a C clip falling off? It seems like that design would be terribly unsafe. I don't know if this is even possible. Anybody have hands on rebuilding experience with one of these?

 

[nooberiffic]

I have rebuild one. Its fairly easy. Just remember to soak the replacement clutches in gear oil or the LS additive for a night before you put them in.
Like I said, im no mechanic, but that clutch pack (clutch pad, spacer, spring) is what keeps the axle from moving in. If that is the only direction its going (in and out) it seems like that might be where your problem is at.

 

[gijoecam]

It's perfectly normal. A c-clip-retained rear axle (like the Ford 8.8) will have some play in and out. It's perfectly normal and nothing to worry about. So long as the axle can't slide in so far that the c-clip slides off the axle shaft (which would quickly become an obvious issue as the axle shaft walks out of the axle tube), it's perfectly fine.

 

[nooberiffic]

maybe I packed it too tight, but mine has no real measurable movement in. a slight hint of movement if you push hard in.

 

[gijoecam]

maybe I packed it too tight, but mine has no real measurable movement in. a slight hint of movement if you push hard in.

They'll all have SOME movement in and out. The c-clip sits in a depression in the face of the spider gear. The cross-pin stops the shaft from sliding inwards, and the c-clip stops it from sliding outwards. Depending on how much clearance there was to start with, there may be a few thousandths, or up to the thickness of that c-clip (and then some). If it's 1/8" or so, it's nothing to worry about. If you get much more than 3/16", you run the risk of the c-clip falling out and the axle shaft coming out.

Again, perfectly normal and nothing to worry about. If it was a full-floating axle, then I'd be worried, but it's not.