M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Engine + Driveline => Topic started by: Froos on December 27, 2006, 05:05:01 PM
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Hi all, im new to the LSD's. On my car there is a 4.10 diff which is open. I dont know how to identify if it is a large or small one.
I just got back from a trip to germany where i picked up a 3.73 LSD (for very little money), I know i cant use it because the ratio will make my car drive like a dog. The reason I bought it to trade it for a a 4.10 LSD over where I live.
But the seller told me that usually all LSD's are of the large case type, is this true?
If this is true, what is involved in using large case on a car which used to run small cases?Different output shafts maybe?
Ive added some pics , first is the old, second pic is the new one
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LSDīs are not big in general, itīs all model dependent,
a big E30 diff will have two bolts on the bottom side where the aluminum bolts to the diff housing,
left - small
right - big,
you can see the single bolt in the small one and two in the big one
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To be technically correct - there's 3 sizes: Small, Medium and Large.
Our 318 e30 cars have the small case.
The 6 cyl e30 cars and the e30m3 have the Medium case.
E38s etc have the Large case.
I know for sure the small and medium cases came with LSD. I am not too sure on the big cases.
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Ok i went to the garage and I bought a medium size diff, can I just swap it with the small one without buying new parts?
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Speaking only about E30's there are two case sizes. The small one, like you have on your car and the big one which is the LSD you bought.
4.45 , 4.27 , 4.10 , 3.91 are in small cases.
3.73 , 3.64 , 3.25 , 3.23 , 3.15 , 2.93 , 2.73 are big cases.
There are some rare 3.91's in big cases. Big case diffs are used on 6cyl (320,323,324,325) and the small ones in 4cyl.
My oppinion would be to keep the 3.73. There isn't such a big difference if you'd stick a 4.10.
And yes, if you now have a small case diff you can fit a big case one plug and play and vice-versa.
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And yes, if you now have a small case diff you can fit a big case one plug and play and vice-versa.
Excellent! Many thx guys!!
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I personally know of a person who wasn't able to get a diff from a 6 cyl e30 to fit in a 4 cyl e30. I have also heard of cases where the half shafts supposedly don't always fit and vice versa. My guess is it comes down to the exact year of the car in question.
Your 4.10 LSD should be fine though.
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I just put a medium case 3.46 from metrix motorsports in my car, it seems it all fits
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Your 4.10 LSD should be fine though.
Thats the thing I dont have one
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I'd like to know why everyone wants lower gearings. The power in the M42 is situated between 4000 rpm and 6000 rpm (stock anyway) so you want it to rev higher quicker. Maybe I'm missing something?
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I am picking up my 3.73lsd med case tommorro. I want it for the turbo^^
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i put in the 3.46 cuase i have an e36 tranny. 1st gear will be longer (better cause my light weight flywheel) and the rest will be shorter!
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most of the information above seems correct, but i have a few corrections...
i believe the 4.10 also came in the e30 m3 and was a med or large case.
it also came in automatic 325i's, so that should be med or large case as well..
3.91 also came in the ix and larger cars so that could be med or large case..
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i put in the 3.46 cuase i have an e36 tranny. 1st gear will be longer (better cause my light weight flywheel) and the rest will be shorter!
what does the length of the gear have to do with weight of flywheel? Nothing, the lightweight flywheel just makes your engine rev faster. :confused:
Bentley quote for E36 Getrag 200/250 gearbox (left) and Getrag 240 gearbox (right)
1st 4.23 1st 3.72
2nd 2.52 2nd 2.02
3rd 1.66 3rd 1.32
4th 1.22 4th 1.00
5th 1.00 5th 0.81
So the 1st gear in the E36 gearbox is actually shorter than the E30 one. :)
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(http://www.orbitfiles.com/download/id1126357348?sid=0a827317b0ef597a959684175090b710)
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what does the length of the gear have to do with weight of flywheel? Nothing, the lightweight flywheel just makes your engine rev faster. :confused:
Bentley quote for E36 Getrag 200/250 gearbox (left) and Getrag 240 gearbox (right)
1st 4.23 1st 3.72
2nd 2.52 2nd 2.02
3rd 1.66 3rd 1.32
4th 1.22 4th 1.00
5th 1.00 5th 0.81
So the 1st gear in the E36 gearbox is actually shorter than the E30 one. :)
yes but with my 3.46 it will be longer. Also i thought first gear was too short already and with my engine work and the lightweight flywheel it would go through it even faster
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dont use first gear
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well i've just taken my 3.64 lsd (rebuilt with ford clutch pack) and replaced the gearing to a 4.45 out of a e34 520 and it's a hoot now, much more rally car like. whats this about gearbox swapping? does the e36 318is box have different ratios then? does it fit? kev
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well i've just taken my 3.64 lsd (rebuilt with ford clutch pack) and replaced the gearing to a 4.45 out of a e34 520 and it's a hoot now, much more rally car like. whats this about gearbox swapping? does the e36 318is box have different ratios then? does it fit? kev
yes it fit perfectly.
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hmm magic that'd give me...
1st - 23mph
2nd - 38mph
3rd - 58mph
4th - 80mph
5th - 97mph.
imagine that in the lanes...
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btw how'd you get it to rev to 7200rpm??? and what does 4 bolts in the sump mean?
cheers
Kev
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I have chip for 7200.
http://www.m42club.com/forums/showthread.php?t=594
5 bolts ;)
btw how'd you get it to rev to 7200rpm??? and what does 4 bolts in the sump mean?
cheers
Kev
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sorry i meant 5 bolts, is the engine happy to rev to that standard then? mine is 180,000 miles old and still original so she's tired, what else have you done to your's to get the extra 1000 rpm? and what is the significance of 5 bolts? i don't understand what you mean?
thanks for your help
Kevo
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ah just read the writeup now on the bolts explanation, could have been nasty.
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i tried 3.73 diff on my iS, gear ratios were never right so i changed 4,27
long ratios on little engine, no no
only thing on that 3.73 diff was that lock kept 110nm, on 4,27 keep only 50nm :(
by the way, how much stock lsd slip nm is?
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I have a small case 3.91 LSD from a 84-85 318i that had the M10 engine. These are hard to find but they are out there and bolt right up and dont weigh as much as the medium case diff's. If you go to metric mechanics web sight and look at there diff page there is a brake down of the ratios and torque handaling of the different ratios.
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whoaa... nice website! thanks dino245 :)
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I was just reading through some of the threads relating to diff ratios and trying to decide what I'm going to do with my car. I have 2 sets of wheels. One with 195/65R14 and another with 195/60R14 Falken Azenis tires for weekend fun. I crunched some numbers in a gear ratio calculator with both tire sizes combined with every gear ratio that might have the remote possibility of making sense. I still haven't decided what I'm going to do but I thought others might find these useful. Keep in mind that the speedometer is inaccurate and it won't correspond with these numbers. Starting from the shortest ratio to the tallest.
(http://farm1.static.flickr.com/191/511927291_b44c08f8a2_o.jpg)
(http://farm1.static.flickr.com/213/511927323_6fa1761eab_o.jpg)
What I have on the car right now.
(http://farm1.static.flickr.com/213/511886652_cbedcb05be_o.jpg)
My stock tire size and differential.
(http://farm1.static.flickr.com/231/511886664_d1dc947c06_o.jpg)
(http://farm1.static.flickr.com/224/511886624_abc5519c6f_o.jpg)
(http://farm1.static.flickr.com/227/511927249_a3ae89bb7b_o.jpg)
(http://farm1.static.flickr.com/196/511886606_695e0082f8_o.jpg)
(http://farm1.static.flickr.com/189/511886614_b8027bb165_o.jpg)
(http://farm1.static.flickr.com/220/511927171_c4857d3774_o.jpg)
(http://farm1.static.flickr.com/190/535665000_6513535d9f_o.jpg)
E36 318ti Final drive is almost identical to our 4.1.
(http://farm1.static.flickr.com/210/535781129_bc708ba002_o.jpg)
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Just for comparison sake, my beater NEON ratios. This is a base SOHC 2.0, no PS, no AC, etc, about 2300 lb. The neon is just as quick off the line but has longer legs in any given gear.
(http://farm1.static.flickr.com/195/513693058_7ace1a99f2_o.jpg)
Right now I'm leaning toward this ratio as a good middle of the road option.
(http://farm1.static.flickr.com/189/511886614_b8027bb165_o.jpg)
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Just for comparison sake, my beater NEON ratios. This is a base SOHC 2.0, no PS, no AC, etc, about 2300 lb. The neon is just as quick off the line but has longer legs in any given gear.
(http://farm1.static.flickr.com/195/513693058_7ace1a99f2_o.jpg)
What program did you use to generate these nice charts?
EDIT: This is the calculator I have used: http://www.unixnerd.demon.co.uk/revs.html