Problem: LSD whining noise

[guuskolo]

Hello guys,

I swapped to a limited slip diff last week (best decision ever).

I bought it second hand, so I disassembled it partly to check what condition it was in. I found that the bearings were like new, and the breakaway torque was nicely within spec (mine had 63nm, spec is 50-70nm) so I decided to call it a day and re-assemble the thing. Afterwards I put 1,7L of oil in it (KroonOil Gearlube Racing 75W-140 Limited Slip) and installed it to the car.

Now, during my first test-drive, I noticed that there was an o-so slight whining noise coming from the rear of the car. Note that the noise is really soft, only detectable when on new and clean asphalt. As the diff is the only changed part, it has to be the diff..

My question: Is this a problem, what could cause it, and how do i solve it?

[guuskolo]

update:

spoke to a local mechanic, and he mentioned it could either be the pinion bearing (they tended to wear faster) or indeed the 'meshing' of the pinion&crown.

If the noise was very slight, and I had opened the diff before, it had no use to do so again. He recommended to just continue as is, and if it got worse to start investigating.

[reggid]

Will probably be pinion preload or bearings themself as they do wear often

How did you check bearings ? I.e How much did you pull apart to check ?

Meshing should be fine unless someone screwed with the shims

[guuskolo]

- I removed the diff body (that which has the crown wheel attached)
- visually inspected the bearings on the body, and in the housing.
- rotated the pinion shaft (check for consistency and smooth rotation)
- checked the breakaway torque of the LSD-pack

what I did not do (and regret now )
- check pinion rotation torque
- check pinion/crown mesh

[paultv]

The most important things are not mixing up the shims and installing a new crush washer and setting the pinion preload.... did the seller tell you it was fine and quiet? I personally would have fitted the diff and driven it with fresh oil before stripping it down....to assess what I had in the first place.....I would imagine every diff of this age would show signs of use and wear, normally a whine or clunk unless it's been rebuilt of course. Does the whine change under load, coasting, slowing down? If not it's probably a bearing, most likely input shaft, probably best to live with it and fix it if it becomes a lot worse, they're pretty bullet proof.

Paul

My 3.46 whines when coasting.....preload a bit slack !

[reggid]

yeah if not that loud let sleeping dogs lie.

Without a press it would be a pain to change pinion bearings and setup with correct drag. With the right tools its very easy though.