LSD rebuild and ratio change

[stuartgallafant]

i think its still available

[gcorky]

oh Gareth ,now its apparent lol....

[stuartgallafant]

oh Gareth ,now its apparent lol....

eh?

[gcorky]

oh Gareth ,now its apparent lol....

eh?

he sent p.m re something ive just bought

[gareth]

spotted me!!!!

having done some lot of maths on final drive ratios (including the effects of tyre sizes) i reckon i ideally need a 3.25:1 ratio. this is because of the small rolling diameter of my tyres. the 3.25:1 on my tyres works out about the same as a 3.46:1 on the 'right' size tyres and this is generally regarded to be the best ratio for a 335i.

my current setup works out the same as anyone else with the right size tyres running a 335i on a 4.1:1 diff!!!! that explains why 1st is useless then!

[gcorky]

3.15 for my blown bitch suits me!!

[gareth]

to drag this up from the dregs again....
i've now got a wounded M3 3.25:1 diff, in need of a new input shaft bearing. is this available anywhere?

i've also found these:
http://www.nexternal.com/bimmerworl/Product584
costly but uprated...

[stuartgallafant]

are you going to replace the bearing yourself? if not, send it to JP Race, based in Silverstone near the track. My mate had an E30 3.91 LSD rebuilt there, and he was really pleased with the result

[gareth]

i intend to do everything possible myself! i'm a very stubborn engineer and will never admit defeat!

[stuartgallafant]

so you're prepared for all the grief then? heard its all pretensions, clearances and what-not...

i could probably get the settings for you if you need it

[gareth]

hell yeah!!!!

any info you have would be great!

[Templ8e30]

One of the input bearings is a shrink fit, you'll need to carefully grind the old one off (grind it flat parallel with the shaft until it 'pings' loose).

To fit the new bearing I put the shaft in the freezer overnight, heat the bearing up in the oven (no more than 100 degrees). Take the shaft out of the freezer and put it in a bin bag, empty the contents of a CO2 extinguisher onto the shaft ( I got mine down to -50 degrees) then very swiftly slip the bearing over the shaft. Be quick, after a few seconds it's locked on solid.

Your local bearing factors will be able to get the bearings, they are inch size tapered roller bearings.

Cheers,

Iain T

[gareth]

fantastic. cheers iain!

why should i not heat the bearing more? i have the use of some nice ovens at work that will reach 350°C. as an alternative, i have a precision 100 tonne press that i made that i can use.

[Templ8e30]

Using heat much more than 100 degrees can alter the tempering and hardness of the bearing.

Cheers,

Iain T

[Quaser]

as i belive my LSD is fairly tired ('sometimes' doesn't lock up properly), i'm wondering about rebuilding it while i do a total rear suspension refit and also if possible swapping the rato for something better suited for my M30 while i'm at it (mine is a 3.91 at the mo.)

Hi Gareth

Quick question, is this same the LSD that you sold me - advertized as 'it's in good nick. no leaking. no whining, rumbling or scraping noises whatoever. it locks up well too. it could use a new diff bush as there are some cracks in it. that said, it still holds well. it's from a H reg 325i touring, not a thrashed unit from a sport! '

Q

[Quaser]

Back to the top please - as i need an answer for the above

[gareth]

nope, that went on my mates car ages ago!!! he was selling his 325i tourer with LSD so a few beers his way later and mine had a better LSD he even swapped if for me while i was at work

how did you get on fitting it by the way? all your knuckles intact?

[gareth]

i have finally pulled my thumb out of my arse and started dismantling my 3.25 LSD pack for inspection.
there is evidence of someone being there before me so it may well have had a rebuild before. the friction plates measure up at 1.95mm and have the original grooves in the face still intact. these measure up at 1.75mm.

are the plates still good to use? they certainly 'look' ok (still textured all over) and i'm fairly skint at present!

EDIT:
i've just had a close look at the 3.25 crownwheel and pinion i bought and due to an input bearing failure, it's totally screwed!!! the planet gears in the LSD pack also seem to have revieved a few hits from a washer getting in there! argh!!!!! i'm so sick of this now!

[hoshy]

wow - loads of info here.

Wasted a good 30mins at work reading it all and have one big question.

Can anybody recommened somebody in Surrey/SW London preferably who can do a 4 plate upgrade ?

[Bob_S]

all the bearings can be bought from BMW for circa £15 each - there are 4 in total.
I have been looking at the same thing I'm getting my small case 3.25 lsd pack transfered to my small case 4.1 clutches are in good condition and so are the bearings on both diffs so I'm sorted! incidentally I have 3.25 pinion and crown wheel up for grabs... pinion and input is still in the casing... just wants an lsd pack bolting in

[Bob_S]

post to notify me of replys.. forgot to add

[gareth]

time to drag this thread up methinks!

i've made up the tooling to enable me to accurately hold and machine the 30° ramps. they're HARD!!!! machining with a replaceble tip carbide cutter ato wrok earlier was fun lots of sparks and smoking swarf flying everywhere (inc down my neck )

how's everyone else getting on?

[stuartgallafant]

now im dragging this up again!!

just in the middle of completely renovating the rear of my E30 so i've got the diff off and im thinking of actually doing this now

gareth, how did you get on?

[JungleGus]

can wait to see this happening guys - a mate of mine had a write up handy - i'll try get it off him

[gareth]

i've sidelined this for the time being while i've been getting the LPG sorted... should be attacking it again soon.

[stuartgallafant]

lol! what did you find then gareth?

did you hit any major problems?

[gareth]

yep, lack of time, money and motivation!
oh, and the car getting it's arse bent at the beginning of the year. i've been concentrating on more important bits recently but it hits the road again on saturday so i'm sure the lack of LSD will annoy me into action before long!

[stuartgallafant]

thats my motivation! i'm having to put my original 4.1 small case diff back in while this ones out on the rebuild!!

[Chase007]

A lot to take in here on this subject!

[Morat]

Did anyone consider putting a quaife diff in instead?

[Andyboy]

Here are some BMW's with the medium case (Type 188) diff and the rarer ratios:

E28 518i uses the 4.1 (revvy)

E28 520i (later ones on D-E plate) use a 4.27 (very revvy)

E34 520i 12v (88-91) uses a 4.44 (very, very revvy). Some manuals use the 4.44, all autos use it.

E34 525i 12v (88-91) uses the 3.73 (nice compromise between a 3.64 and the 3.91. Probably the best ratio for a 325i and a 2.7).

All of these diffs are £10 - £50 and the crownwheel/pinion can be used in a 325i LSD.

[stuartgallafant]

right, after driving around for a few weeks with an open diff, i opened the can of motivation to get my LSD rebuild into gear... no pun intended!!

I've stripped the diff down just leaving the pinion gear well alone and at the moment im leaving the output bearings alone too!!

The crown wheel and drum assy is out and upon inspection everything seems ok. no loose bolts like iain temple had, which scared the hell outta me!!

i gotta wait till the end of the month now to get the atlas repair kit as im borasic. My mates old man is gonna do the machining bits for me, so with any luck it'll be done within 6 weeks?

just a question though... when i remove the clutch pack from the crown wheel, will i have to remove both the bearing races? if i dont that'll be great, coz i've heard resetting them is a bogus job!!

any other tips people wanna throw over will be great!

i'll put some pics up soon

[stuartgallafant]

^^^^

BUMP

[stuartgallafant]

ANYONE??!!

[stuartgallafant]

Still no-one?!