Author Topic: Urgent diff question! (Read 4038 times)

Vladi · « **on:** July 30, 2006, 02:09:57 PM »

Urgent question guys!
I have a friend with a 3.23 small case LSD in good condition (no humming).
I currently got a 4.10 LSD also in good condition on my car.
I'm going to install a M42 1994 E36 engine (140hp base)with the complete M20 clutch kit + E30 M40 gearbox + chip (i don't know how good it is, yet, all i know is that it goes up to 7000rpm) + some small mods, it would go somewhere around 160hp. I will dyno test it after the package is in.

So, what would you guys say, go for the 3.23 LSD? I'm not making my car especially for races or track use (i don't even have a track where i live), i plan to use it for long trips and a few races.

What should i check the 3.23 for to see if it's good, except the humming?

Thank you!

E30 Four cyl gears (Getrag 240):
Gear Ratios km/h    mph
1   3.72   45.97 28.57
2   2.02   84.63 52.59
3   1.32   129.84    80.69
4   1.00   170.87    106.19
5   0.81   212.26    131.92

Differential:   4.10
RPM:    6500

E30 Four cyl gears (Getrag 240):
Gear Ratios km/h    mph
1   3.72   58.35    36.26
2   2.02   107.42    66.76
3   1.32   164.81    102.43
4   1.00   216.89    134.80
5   0.81   269.43    167.45

Differential:   3.23
RPM:    6500

nickmpower · « **Reply #1 on:** July 30, 2006, 02:16:42 PM »

Wizard · « **Reply #2 on:** July 30, 2006, 06:08:39 PM »

I don't think a 3.23 is a good choice for the m42 engine...Would prob get some good fuel milage, but I think it would be too "sluggish" around town and real dog on a race track...3.91 would be the lowest I would go on an M42....Keeping the 4.10 is your best bet..

silverblades181 · « **Reply #3 on:** July 30, 2006, 09:25:06 PM »

Quote from: Wizard

I don't think a 3.23 is a good choice for the m42 engine...Would prob get some good fuel milage, but I think it would be too "sluggish" around town and real dog on a race track...3.91 would be the lowest I would go on an M42....Keeping the 4.10 is your best bet..

+1

Or find a 4.45 LSD off a 318ti auto

now that's cool gearing.

2002maniac · « **Reply #4 on:** July 30, 2006, 10:28:30 PM »

If you think you need higher gearing, look for a 3.91 out of an early 318i.

Vladi · « **Reply #5 on:** July 31, 2006, 05:11:29 AM »

Thanks for the input, i'll stick to my 4.10, then.

I've also got a 4.27 small case open diff...at one moment an LSD swap from one to another crossed my mind but i find it pointless.

M42boy · « **Reply #6 on:** July 31, 2006, 03:23:49 PM »

Stick with the 4.10... These cars need all the low end umph they can get! These cars are already slow enough... with 3.23 it would be DAMN SLOW!

Vladi · « **Reply #7 on:** July 31, 2006, 04:52:30 PM »

Advice noted. I'll stick with the 4.10.

///M PowerBG · « **Reply #8 on:** August 02, 2006, 06:32:12 AM »

What will happen if you put a gearbox from E36?...

1-4.23
2-2.52
3-1.66
4-1.22
5-1.00

the standart diff for E36 is 3.45,so the 3.23 will make it a little longer....?

Vladi · « **Reply #9 on:** August 02, 2006, 11:23:18 AM »

If i put the standard gearbox from the E36 (and thus giving up on the M20 clutch conversion) and use my 4.10 diff i end up with a top speed of 160km/h/99.4miles/hour. These are exact figures, i've calculated.

If i would have used the 3.23 LSD + E36 gearbox i would have had the same ratio as the stock E36....but i don't want that.

By doing the clutch swap i get much better performance.:rolleyes:
So the install is E36 '94 M42 engine with M20 clutch swap + E30 M40/M42 (the gearboxes are the same) gearbox + 4.10 LSD.

///M PowerBG · « **Reply #10 on:** August 04, 2006, 02:34:53 PM »

Quote from: Vladi

If i put the standard gearbox from the E36 (and thus giving up on the M20 clutch conversion) and use my 4.10 diff i end up with a top speed of 160km/h/99.4miles/hour. These are exact figures, i've calculated.
If i would have used the 3.23 LSD + E36 gearbox i would have had the same ratio as the stock E36....but i don't want that. By doing the clutch swap i get much better performance.:rolleyes:
So the install is E36 '94 M42 engine with M20 clutch swap + E30 M40/M42 (the gearboxes are the same) gearbox + 4.10 LSD.

So if i use a E36 gearbox i cant do the M20 (flywheel + clutch conversion)?...i am asking because i have E36 and i want do it?

FL318is · « **Reply #11 on:** August 04, 2006, 02:38:02 PM »

Would a 3.73 LSD be worth it or am I just way too noob?

silverblades181 · « **Reply #12 on:** August 04, 2006, 03:15:01 PM »

it's kinda low gearing, since the M42 gets his power from 4000 rpm and up (rougly) it will take you longer to get there and the car will be sluggish. You'll be able to keep the gears longer and get higher top speed (theoreticly) though. The 4.10 is the best gearing for street usage in my opinion, and if you get a higher reving M42 (modded) then a more aggressive 4.45 would be in order. My 2 cents.

Vladi · « **Reply #13 on:** August 04, 2006, 07:15:27 PM »

Quote from: ///M PowerBG

So if i use a E36 gearbox i cant do the M20 (flywheel + clutch conversion)?...i am asking because i have E36 and i want do it?

No, unfortunately you can't. I've tried it with the E36 gearbox and the clutch disc and plate don't fit.:confused: