LSD Units - Ask me anything.

[taylorstattoo]

HI, IV BEEN TRYING TO WORK OUT WHAT DIFF I NEED FOR MY TOURING AS DOING A 328 M52 CONVERTION, IV BEEN TOLD E36TI`S HAVE THE SAME DIFF`S BUT ARE MOSTLY SMALL CASE,

THE OTHER THING IS HOW TO WORK OUT THE NUMBERS ON THE DIFF,, IS IT 3, WHAT EVERS ARE QUICKER WITH REVY TOP END OR 4. WHAT EVERS. ??/ WHITCH WAY AROUND IS IT..

[ross_jsy]

What diff you require will depend on what gear box you use.

Not sure what you are getting at but a 3.64 will give higher top end with the loss of acceleration compared to say a 4.45.

[randomspeedfreak]

what does lock when given as a percentage actually refer to,

both physically inside the diff and when driving the car?

so for example, what ramp angles would a 40% lock diff have? what characteristics will this implement over say a 25% lock?

[DanThe]

Never seen an 8 plater bumlot?

[taylorstattoo]

What diff you require will depend on what gear box you use.

Not sure what you are getting at but a 3.64 will give higher top end with the loss of acceleration compared to say a 4.45.

thanks, sorry, ill be using the original box that came with the m52b28 in the 328i e36.. i would like more speed off the line rather than top end as there aint no highways near me anyway lol,

but obversly i dont want to be stuck with a top end of 80mph..

[grumpyoldman]

After some bolts for diff rebuild the ones that are like toffee in a e30 LSD size M8 _1 after 2 sets if possible

[Demlotcrew]

These are what you need.

http://www.ebay.co.uk/itm/M8-x-18-FINE- ... 5899b94cea

If you want the proper half head bolts, I can source some for £40.

If you are not in a hurry, PM redcar he has a link to an american supplier who does 8 bolts for £10 posted.

Andrew

[TPS]

Hi Andrew

I knew nothing about Diffs., My Touring has a M42 lump in, if I changed the 4.10 diff., to a 3.91LSD , how different would that make to the car? Would an LSD make any difference in the current snowy conditions?

[Demlotcrew]

Phil,

I have had a 3.91 coupled to an M42 and I thought it smoothed out the power band too much, the engine just doesnt have the torque so if it was my car, I would hold out for a 4.10 or fit the 3.91 but expect to loose some drivability.

In snowy conditions a ZF clutch LSD would be very beneficial, but you have to be very careful and be ready to catch any skids!

[ross_jsy]

Diff will make a huge difference in snowy conditions.

Taylorstattoo, I'm not sure what diff you need but it needs to be a lower ratio. Something like a 3.15 would probably be ok but best get someone else to verify as I stuck with an e30 box when I swapped.

[TPS]

Thanks Andrew

[Demlotcrew]

No worries Phil

[Demlotcrew]

These are what you need.

http://www.ebay.co.uk/itm/* I tried to use text speak but the text speak filter stopped me *-x-18-FINE-PITCH-1MM-ALLEN-CAP-12-9-BOLTS-4-PCS-FINE-THREAD-/380536179946?pt=UK_DIY_Material_Nails_Fixing_MJ&hash=item5899b94cea

If you want the proper half head bolts, I can source some for £40.

If you are not in a hurry, PM redcar he has a link to an american supplier who does 8 bolts for £10 posted.

Andrew

Please hold off buying these, I need to double check the length of the bolts!

[maggspower]

These are what you need.

http://www.ebay.co.uk/itm/* I tried to use text speak but the text speak filter stopped me *-x-18-FINE-PITCH-1MM-ALLEN-CAP-12-9-BOLTS-4-PCS-FINE-THREAD-/380536179946?pt=UK_DIY_Material_Nails_Fixing_MJ&hash=item5899b94cea

If you want the proper half head bolts, I can source some for £40.

If you are not in a hurry, PM redcar he has a link to an american supplier who does 8 bolts for £10 posted.

Andrew

Please hold off buying these, I need to double check the length of the bolts!

16mm is the correct length.

[Demlotcrew]

I will have a measure tonight, in any case these are 16mm long.

http://www.ebay.co.uk/itm/M8-x-16-FINE- ... 53f1b72b60

Andrew

[Mikey_Boy]

A couple more questions now:

1. 3.25 diffs - rare or not?

2. Best lock percentage for trackdays?

Very general I know, but asked for the following reasons - firstly, I am considering either a 3.46 or 3.25 diff for my car with the S14 fitted and secondly, my other trackday car uses about 40% lock under power and this seems to suit trackday work very well - it can be a subjective thing of course and set up dependent, but any guidelines on what is too much / too little would be helpful...!

3. Lastly - what would be your ideal LSD setup that would fit an E30?

[Demlotcrew]

Hi Mike,

I will do my best to answer your questions

1. No a 3.25 is not rare, they are fitted to almost all E30 M3's. They can be sourced and often do come up on the forum and eBay.
2. This is so tricky, everyone is different, but I recently spoke with someone who has actual telemetry data and it all shows that a 70% lock LSD is too high, even with the right driver the lap times were slower. Then there are those that swear by a high locking LSD so I think it's best to attack the problem in the following way.

Rebuild your stock 2 plate LSD in to 4, keep the stock 45° ramps and try it out on track, if you still feel like you need more lock take the ramps out and have them ground down to 30° to get 70% lock

If you can source a 3.46 it will be absolutely perfect for the S14 ;) this is exactly what I'm building.

3. My ideal LSD would be something like a drexler http://www.drexler-motorsport.com.au/products.html they are very light, hard wearing, fully adjustable and can handle some serious power, one of the best LSD manufacturers.

But since I cannot afford such a luxury I have had to settle for a GrpN replica ZF 188 LSD. This uses the later E36/Z3M case with four large openings, four Porsche sintered clutches, four 2.0mm dog ear plates, polished 45° ramps and a few little tweaks here and there (mainly to do with preload).

Hope that helps

Andrew

[Supafly]

I'm planning on refreshing my 3.46 z3m LSD this summer. Can I ask where you got your clutches and dog ear plates from?

Gareth helped me when I refreshed my old 3.73 factory fitted LSD with clutches by pointing me to drive and traction. When re-fitted to the car that LSD was noticeably harder to turn one wheel than my 3.46 currently is. Have you increased the pre-load on yours? I'm also interested in doing this while maintaining standard ramp angles. From memory this is originally done with a belleville washer, can upgrades be bought easily? or did you add washers as shims?

[randomspeedfreak]

what does lock when given as a percentage actually refer to?

both physically inside the diff and when driving the car?

so for example, what ramp angles would a 40% lock diff have? what characteristics will this implement over say a 25% lock?

cheers,
Matt

[Jimbob]

Clutches can be bought from Porsche, along with 2mm or 2.1mm dog ear plates depending on your preference.
Removing the washer and adding an additional clutch and plate will increase to about 40% lock or so I'm led to believe.
Seen a few pics of Andrew's diff, looks the bollocks! If I had the cash I would've followed his advise but instead chose to keep my ramp angles standard due to cost, I think it was about £350 replacing all the seals, clutches, bearings etc, on top of the price of an LSD in the first place, another £150-£200 to cover an additional plate and clutch and the machining of the top cap was pushing it too far.

[Supafly]

Thanks for the pointer Jimbob.
I've read the same, I've also read that this causes an imbalanced unit with two clutches on one side to one on the other. However this can be remedied by taking 4mm off the top cover and doing the same again and having a four clutch lsd.

My current thinking is to keep the stock ramp angles and only do new clutches/dog ear plates, keeping it standard.

[MillRat]

A question; the "percentage lock" is not an accurate method to describe the amount of resistance as "percentage lock" relates to the engine power/torque. Therefore, isn't stating the breakaway torque a better measurement?

I ask this because as I understand it, 70% lock equals a breakaway torque of something like 120 ft lbf (160 Nm) and is thus 70 percent of the engine torque (160-170 ft lbf or 220-230Nm for a standard 325i). If I was to build a much more torquey M20 (or use another more torquey motor), the "percentage lock" becomes some smaller number (depending on the torque of the new engine that is). One would then think that the 2 LSD's are different as the % lock values would be different, when in fact they are exactly the same LSD. Therefore, to accurately compare one LSD to another, the breakaway torque should be stated instead.

As I said above, this is my understanding.

[Demlotcrew]

A set of ramps on eBay.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... SS:GB:1123

[urfy]

Any questions about LSD configuration and possibilities?

Andrew

Hi, wonder if you can decide which diff to go for?

I am re-building my tech2 325i sport but going the 2.7 route using my 2.5 block, crank & flywheel have been lightened & balanced and I am using a E30 323i dogleg gearbox.

I have a standard sport diff (I thinks its the S3.91), a S3.73 & a S3.25, so which will do what and which one would be the best?

The car will be for road use and not tracked. Any advice will be appreciated.
Thanks
Ivan.

[DanThe]

Good info here - http://50.116.97.200/~mm/pdf/Differentials.pdf

I found this under the bench so took it apart for a nose/clean up the other day -






Plan is to bodge it into my track car to compare to the 70% locker Gareth sorted for me

[Demlotcrew]

Finally! Been waiting for a few weeks now, BMW MS LSD cap has turned up.

I have never been happy with skimming the stock plate as the most you can run is 4 clutches which wear way too quickly.

This cover gives me a huge selection of configurations (up to 6 clutches are possible). But mainly my plan is to run it with thicker carbon frictions plates that offer unparalleled performance advantages.







Any questions please ask away.

Sorry for all those that have asked for ratio calculations, I have yet to get back to everyone, just finding the motivation to do the sums!

[Mikey_Boy]

^^^^

I can really recommend carbon friction plates - I have them on my tweeked Porsche Turbo (964) - it transformed it from a tail happy monster to something much more controllable that gets better and better the hotter it gets..

[Demlotcrew]

Thanks Mike,

Im really looking forward to getting it all together and I think the better 3.46 ratio is going to give me a nice acceleration boost as currently I have an M Coupe 3.15 2 way.

Can you really tell the difference between the two clutches? I know all the good stuff of the Carbon from what ive read, but do they really make such a nice improvement?

[AdamGardner]

can you still get the end plates seperately then? mine is damaged from snapping an output shaft.

[Demlotcrew]

I believe you can buy them from ZF directly. I have a stock one going spare if you're interested?

Sadly it won't work with a stock 2 clutch LSD as its been shaved down.

[taylorstattoo]

half way though my m52 conversion now. but have ended up sticking to the m40 318 touring box and diff..
what sort of drive will i expect to get, will i need to change the diff,,

[Demlotcrew]

Im going to try and source the data again, and hope to get back to everyone with some recommendations.

[AdamGardner]

id be interested in that, my diff is a 4 plate unit in a rally car

[Mikey_Boy]

Can you really tell the difference between the two clutches? I know all the good stuff of the Carbon from what ive read, but do they really make such a nice improvement?

^^^ Oh yes - far more progressive when they are hot - a little more 'jumpy' when cold - the best thing being you can feel the 'bite' far more easily but rather than that spitting you off, it's easier to control - difficult to explain, but I hope you get the gist!

[TommyM]

Hi i have my car up on axel stands at the moment and thought id check what diff it had on the tag it says 3.73 i got told it had a welded diff when i bought it but upon googling the ratio it comes up with lsd's. did they also make this ratio in an open diff also? Thanks for any help.