Limited slip differential chatter GTS

[6502Nerd]

Just want to check with folks on this one..
Diff oil changed as part of warranty work to fix leaking seals. Ever since the car clicks and chatters away when turning, especially noticeable at low speed.
It's terribly disappointing to drive as the diff was as smooth as any other before the oil change.
The garage is going to put in some additive but they say there's no damage being caused to the diff clutches in the meantime.
Have others had this and any success with additives?

 

[cheburator]

Yes, the GKN sourced ///M differentials in the E46 M3 are notorious for chatter. So much that BMW got a specially formulated Castrol 75W140 LSD oil with friction modifiers in it to quieten down the diffs. The Cup differential in my GT3 used to chatter a lot until I started using Motul 75W90 LS oil which already has friction modifiers.

 

[conaero]

Sounds like the wrong oil.

MC Shift 75w90
Auto diff 75w140

Both fully synth

 

[6502Nerd]

Yes, the GKN sourced ///M differentials in the E46 M3 are notorious for chatter. So much that BMW got a specially formulated Castrol 75W140 LSD oil with friction modifiers in it to quieten down the diffs. The Cup differential in my GT3 used to chatter a lot until I started using Motul 75W90 LS oil which already has friction modifiers.

Thanks for this, very useful to know.
I only had one lsd car before, my XKR, but that was very smooth or at least not noticeable. Picked up a friend the other day and he was asking what that strange noise was at low speed.
Getting additive end of the week, hope it quietens down!

 

[6502Nerd]

Sounds like the wrong oil.

MC Shift 75w90
Auto diff 75w140

Both fully synth

I've got the auto, didn't realise the mc shift diff needed different oil, but the garage should know as they're a Maserati indy (fingers are crossed! )

 

[cheburator]

I've got the auto, didn't realise the mc shift diff needed different oil, but the garage should know as they're a Maserati indy (fingers are crossed! )

The MC Shift needs different oil due to the transaxle configuration. The oil inside has a lot of hard tasks - it needs to work well with the synchromesh in the gearbox - so it needs to be slippery, but also it needs to be sheer resistant for the crownwheel and pinion in the differential, and to top it off, it also needs to be not so slippery so that the friction plates in the LSD casette do their job...

 

[zagatoes30]

The MC Shift needs different oil due to the transaxle configuration. The oil inside has a lot of hard tasks - it needs to work well with the synchromesh in the gearbox - so it needs to be slippery, but also it needs to be sheer resistant for the crownwheel and pinion in the differential, and to top it off, it also needs to be not so slippery so that the friction plates in the LSD casette do their job...

Sounds lie a Jack of all trades hopefully not a Master of none

 

[cheburator]

Sounds lie a Jack of all trades hopefully not a Master of none

That depends on the brand. My experience with MOTUL 75w90 LS in my Porsches has been outstanding. The Maserati got serviced by AV Engineering so I am guessing it got the correct Shell oil as recommended by Maserati and so far, has behaved impecably (touch wood )

 

[6502Nerd]

The MC Shift needs different oil due to the transaxle configuration. The oil inside has a lot of hard tasks - it needs to work well with the synchromesh in the gearbox - so it needs to be slippery, but also it needs to be sheer resistant for the crownwheel and pinion in the differential, and to top it off, it also needs to be not so slippery so that the friction plates in the LSD casette do their job...

Yes this is interesting and what the indy explained - in the auto is bolted to the engine and the diff is at the back (obvs), but the mc shift the diff and box are at the back (and connected), so they use different oil..

 

[6502Nerd]

Quick update - got the friction modifier added this morning, and by the time I got home it was already noticeably better. Indy said it might take a few days for the additive to really get into the friction plates, but the 25 mile journey home maybe helped to speed up the process.
I've been waiting for this fix for ages, car is feeling back to what it was like when I purchased it back in March.

 

[conaero]

Thats good news its quietened down.