LSD noise

[goose202]

Had trouble finding an existing thread on this, hopefully it's not my search skills failing me.

I've put a LSD in my VF Calais. Had the back off it before install, everything looked good on a quick, fairly clueless inspection (all the gears looked good, no chips or wear, lash appeared to be in spec). It got some fresh Penrite 75w85 oil which supposedly already contains the friction modifier required.
It's a nice quiet diff in a straight line, no clunks or lash or whines. But on slower sharp turns with a little throttle it has a light grinding or grumbling sort of noise. Sounds exactly like I'd expect for when the clutch plates are moving over one another. Can't really hear any noise if turning with zero throttle or lots of throttle (although the latter might just be drowned out by a bit of lots of throttle noise...)

Anyone experienced this? I guess there's a few possibilities:
1. Diff is stuffed.
2. Different oil might fix it
3. More of the LSD additive might fix it.

 

[07GTS]

add some LSD additive to it see if it fixes as a first option

 

[Smitty]

had the back off...????
you added an after market LSD centre to the diff?
whose? harrop Trutrac?

help to know which type

 

[DavesSV6Tonner]

had the back off...????
you added an after market LSD centre to the diff?
whose? harrop Trutrac?

help to know which type

Sounds to me like he has taken the complete LSD and housing assy from another VF and installed it into his VF.

 

[goose202]

Sorry, should have added more details.
Stock complete diff assembly from a wrecker, untouched by me other than a quick inspection to check no smashed teeth. Didn't even lift out the centre from the housing on inspection.

 

[losh1971]

The stock clutches wear out on these and cause problems with movement in the centre. Best to take it to a diff builder and get his opinion. If the clutches are the problem you will eventually smash your spider gears.

 

[goose202]

Yeah I'm aware of the clutch wear issues on these, that's why I was keen to inspect the teeth before bothering to install it.

I can't imagine the condition of the clutches could be determined without full disassembly, and by that point it may as well be rebuilt anyway?

 

[losh1971]

Yeah I'm aware of the clutch wear issues on these, that's why I was keen to inspect the teeth before bothering to install it.

I can't imagine the condition of the clutches could be determined without full disassembly, and by that point it may as well be rebuilt anyway?

A look at the spider gears won't show you a worn clutch no, they will only show when it's too late. Unless you have a known low KM diff it could well be likely pretty worn out. Given the age of a VE, and that this diff is unlikely to have sat on the shelf for the last 10 years, I suspect it won't be a low km one. A diff tech can measure the resistance of the LSD, which is why I suggested you book it in.

 

[Skylarking]

I can't imagine the condition of the clutches could be determined without full disassembly, and by that point it may as well be rebuilt anyway?

I’d guess a diff builder could have a bench test rig which uses two splines shafts where the diff housing sans rear cover could be inserted. One shaft is fixed and the other can be rotated so the side gears load up through the spider gears turning a little as torque is applied. Such would then compress the clutch packs and the amount the side gears move away should indicate how worn the clutch plates are… But why would a diff shop build such when they’d almost always say to update the clutch packs whenever the diff is out of the car… And such isn’t a full rebuild if gears, preload and such look to be ok, it’s just a clear, disassemble and reassemble with new clutch packs…

Now your in a bind (excuse the pun) since the diff is installed. And if the additive doesn’t fix the issue you‘ll have the cost of removal and reinstall added to the mix. Such could have been avoided had you done the clutches before installing the used diff.

As is, if the additive doesn’t sort things out, I’d replace the clutch packs pronto as a failure will cost you a new pinion gear, crown wheel and bearings… Stuff that almost certainly isn’t needed to be replaced at the moment tomorrow after just one sharp turn under power could be very different

So it sounds like you took a punt and may have lost the bet

 

[losh1971]

From what I have seen if you get onto it pretty quick when the spider gears smash you can save the crown wheel and pinion. I bought a diff with smashed guts yet the crown and pinion will be fine with a small wheel on a dremil. They have a few small burrs but nothing that can't be cleaned up. Bloke who sold it to me said the problem was the gears and the centre was fine. Turns out it was the opposite and the parts that have value will be fine with a 20 min clean up.