LSD failure??

Post Sun Sep 03, 2006 1:57 am

Hi guys,

I not so recently fitted a replacement LSD to my M535i. Its from an M535iA which is a LSD with a slightly higher ratio (giving better gas milage on the motorway) However or recent its stopped drifting in the wet in the usual controlable manner and is drifting like it has an open diff, and quite often is spinning one wheel... I have recently replaced the oil in the diff as well which was not cheap!!! What could be causing it to stop working - I was always told these diffs were bomb proof!

Any ideas?! Can and LSD just stop working as an LSD but still function normally as an open diff??

Post Sun Sep 03, 2006 4:29 am

ok, just been to pick some mates up from Nottingham and on the way back after dropping them home i thought 'empty road, empty car - lets do a test'

For some reason now it is locking just fine, I had some very smooth and controllable drifts going and on more than one occasion, completely unlike earlier today when it was acting like an open diff...

so I now pose a new question, what will cause an LSD to slip more or less...

Post Sun Sep 03, 2006 9:12 am

sounds like you have some issues ahead if a LSD is on its way out it will start to wind its self up then go bang a lsd onlly has roughly 20 hours of lock up time before it is fucked
sorry to be the beare of bad news
is you clutch any good as this can effect lock up

Post Sun Sep 03, 2006 12:53 pm

a higher ratio wont give you better motorway miles. it will be more revvy than a lower ratio diff. anyway, an LSD uses friction clutch plates that lock together when there is a different turning momentum on each side. the clutch plates are under pre-tension and must be exactly the correct distance apart for the lock up to be correct. if theres too much or not enough of a gap, the LSD will either not work, acting like an open diff, or, it will lock up too much, and shatter!

sending the diff away to get rebuilt is a good idea. i well known company such as driveshaft uk rebuild diffs, and i think there price is quite good too

you say you have replaced the oil? if so, did you use the correct oil, and the right amount? you need to use Castrol SLX-XJ for an LSD. if its the same size as an E30 diff, then it will be 1.7 litres

hope this helps

Post Sun Sep 03, 2006 5:55 pm

I definatley used the right oil (so i was told by the specialist anyway), but its not a castrol SLX oil. Its a specialist LSD oil ordered directly from Millers oil for the big case BMW LSD's which I am told is correct for the M535i (which cost about Ã‚£60 for a 5ltr bottle) and it used about 2.0 (but there was a bit of spillage on filling so 1.7 sounds right.

As for 'higher ratio'.. what I meant was longer ratio as the auto is a 4 speed auto appose to the 5 speed manual so takes a lower input rpm for given output if I am correct. Either way the rpm at given speeds is much lower now and the standing start acceleration is alot slower.

Its a bit worring what fowler suggest about it being on its way out. I am using the car as a daily driver for the next 5 weeks until my super uber mega efficient new car arrives but will be using it for nice long drives in future where i dont really intend to be drifting... is the diff likely to pack in casuing any particular issues or will it just act as an open diff?? If it acts as an open diff then im not that worried as I have another m535i which I am either restoring or making into a track car which has a dogleg box and a spot on locker for doing silly things with!

thanks for all the info and help guys

Jon

Post Sun Sep 03, 2006 6:54 pm

Do all diffs have to be looked after that carefully as regards oil? I slapped a 4.10 open diff on my 320i when I got it as I needed a quick replacement, and I've just had bog standard Ã‚£5 a bottle gear oil in it, changed every 10k. Is that bad for it? Sorry to hijack your thread Jon, just wanted to check. And please don't turn the nice M535i into a track car, would be sacrilege - it's beautiful!

Ian

Post Sun Sep 03, 2006 7:01 pm

Firefly2005 wrote:Do all diffs have to be looked after that carefully as regards oil? I slapped a 4.10 open diff on my 320i when I got it as I needed a quick replacement, and I've just had bog standard Ã‚£5 a bottle gear oil in it, changed every 10k. Is that bad for it? Sorry to hijack your thread Jon, just wanted to check. And please don't turn the nice M535i into a track car, would be sacrilege - it's beautiful!

Ian

i think open diffs are ok, its just LSD that need special oil so it doesn't damamge the clutch plates, which are only present in the limited slip diff

Post Sun Sep 03, 2006 7:09 pm

the LSD oil is thicker, so that there is more chance of any torque inside the diff mechanism effecting the lock-up, and as billgates said, to not damage the clutch plates

Post Sun Sep 03, 2006 11:56 pm

Hey Ian,

Dont worry my friend, bit of good old halfrauds own brand gear oil at Ã‚£4.99 is fine for the standard diff... and every 10k should mean the diff will last a life time I would have thought. I dont think the diff in my 520i when I had it had ever been serviced and that was still spot on.

Dont worry, the m535i/track car project is still only an idea/excuse to keep the car. I shall not be desecrating it, its too nice a car to do that too! hehe. First job is to get handy with a welder and get the floor welded up and get it through an MOT!

Post Tue Sep 05, 2006 10:36 am

billgatese30 wrote:
Firefly2005 wrote:Do all diffs have to be looked after that carefully as regards oil? I slapped a 4.10 open diff on my 320i when I got it as I needed a quick replacement, and I've just had bog standard ?5 a bottle gear oil in it, changed every 10k. Is that bad for it? Sorry to hijack your thread Jon, just wanted to check. And please don't turn the nice M535i into a track car, would be sacrilege - it's beautiful!

Ian
i think open diffs are ok, its just LSD that need special oil so it doesn't damamge the clutch plates, which are only present in the limited slip diff

Really how do you know this?

Post Wed Sep 06, 2006 5:56 pm

definatley used the right oil (so i was told by the specialist anyway), but its not a castrol SLX oil. Its a specialist LSD oil ordered directly from Millers oil for the big case BMW LSD's which I am told is correct for the M535i (which cost about ?60 for a 5ltr bottle) and it used about 2.0 (but there was a bit of spillage on filling so 1.7 sounds right

Hi forget MILLERS oil i was getting some strange noises with this oil in,there was too much slip,gave me a loud rubbing noise if turning in first gear,changed to castrol..now perfect..