Author Topic: E30 M3 Diff 4.10 LSD (Read 9420 times)

wadhip · « **on:** June 09, 2008, 06:53:32 AM »

Is that the differential can fitted on my E30 318is ??

tjts1 · « **Reply #1 on:** June 09, 2008, 09:25:49 AM »

Yes but you will be slower.

tony92ic · « **Reply #2 on:** June 09, 2008, 11:08:18 AM »

Why would he be slower? The ratio is the same (assuming he has the stock diff now).

The extra weight from the slightly larger diff wouldn't be enough to be noticable.

And do you mean slower acceleration or slower top speed?

tjts1 · « **Reply #3 on:** June 09, 2008, 01:52:39 PM »

Internal friction and another 35lb on you rear axle. Not worth it to me.

Page 5
http://www.metricmechanic.com/pdfs/metric-mechanic-differential-booklet.pdf

Look for a 3.91 or 3.64 small case LSD instead.

Belteshazzar · « **Reply #4 on:** June 09, 2008, 02:11:41 PM »

I've removed too many noisey used-up small case diffs to worry about the extra weight and internal friction of a medium case unit.

Plus I'm unconvinced it's as much as 35lbs lighter. Have you ever set the two next to each other?
When I did the weight difference seemed negligible, even the size difference didn't seem like much at all.

tjts1 · « **Reply #5 on:** June 09, 2008, 02:31:59 PM »

To each his own. The numbers quoted by MM are accurate. I've weighed 3 differentials so far, 2 small case, one medium case. LSD also weighs an extra 5lb over open diff but thats less to the point. My small case 3.64 came out of a 1984 318i with 220k miles and I abuse it on a daily basis. No noise, no problems. If you want to give up another 3% in drive train loss at the wheels and add 1% weight to the car its a worthwhile swap for some people for the extra peace of mind. Personally I'll just swap another differential when I kill this one. 4.1 and 3.73 medium case LSDs are dime a dozen in the local JYs. The hard part is finding small case LSDs. If you are breaking small case differentials with a 1.8 liter engine, you need to re examine your driving style. Also the differential's maximum torque rating increases as the numeric ratio goes up. A 3.64 is stronger than a 4.1.

Not my picture but it gives you an idea of the size. Theres an easy 35lb hiding between them.

Belteshazzar · « **Reply #6 on:** June 09, 2008, 02:39:34 PM »

no kidding.

well huh. Just read the MM link, + trust your experience. Never would have guessed it was that much.

christophbmw · « **Reply #7 on:** June 09, 2008, 11:01:45 PM »

Quote from: tony92ic;50850

Why would he be slower? The ratio is the same (assuming he has the stock diff now).

The extra weight from the slightly larger diff wouldn't be enough to be noticable.

And do you mean slower acceleration or slower top speed?

slower in the turns, it takes power to fight against the LSD action in a corner....you will notice a difference in the M42, but in low traction conditions the power lost is well made up for in the better acceleration out of the corners.

....not to mention 35lbs in the "ass" of the E30 M42 does give it better balance, sure your adding weight, but its in the right place.

EN318isPDX · « **Reply #8 on:** June 10, 2008, 03:52:21 AM »

wtf is tj smoking. 4.10 is the stock gearing. LSD is better handling (more so when sliding) and putting more power to the ground. stop smoking lsd and get a lsd.

tjts1 · « **Reply #9 on:** June 10, 2008, 07:19:21 AM »

mikedz · « **Reply #10 on:** June 10, 2008, 12:33:55 PM »

Do it!!! I put a medium case 4.10lsd in my e30 m42 and yes you can feel the extra weight but like stated above it is in the right place. All the changes i experienced where for the good handleing was improved dramatically and the extra weight helps keep that happy e30 rearend in place.

mkodama · « **Reply #11 on:** June 10, 2008, 05:54:16 PM »

Well, you could just take out the spare tire to make up for the added weight(unless you have already done that:rolleyes:).

Another added benefit to the medium case M3 diff, is that you can add on the finned diff cover from the M coupe for added cooling on track days and because it looks really cool. M coupe finned diff cover is less than $200 with mounting hardware from the dealer from what I have gathered. part # 33 11 2 282 482 I think

sumyungguy · « **Reply #12 on:** June 10, 2008, 10:25:53 PM »

tjts1 please stop talking and filling up this thread with ridiculous reasons not to use a med case. You may be trying to make yourself sound smart, but your only hurting yourself.

1991318is · « **Reply #13 on:** June 10, 2008, 10:32:51 PM »

I'd say it's worth it just for the extra piece of mind in having a bigger case. Harder to break especially with an m42. And like everyone said, its in exactly the right area, low and in the back. Take out your AC if you want weight reduction, it doesn't help with drivetrain strength, atleast the diff is going to hold up under more pressure.

busbeagle · « **Reply #14 on:** June 14, 2008, 11:30:14 PM »

In our 3 318is's I have changed 3 small case open diffs to medium case 4:10 LSDs. The weight difference is 20 pounds, 65 to 85. 20 pounds is 3- gallons of fuel, not enough to worry about unless its a race car. Still have 2 more to do in some 318i's.

David Beagle
E30s - M3, 318is, 318i, 325 race car

Author Topic: E30 M3 Diff 4.10 LSD (Read 9420 times)

busbeagle