http://cgi.ebay.com/ebaymotors/BMW-LSD-3-46-LIMITED-SLIP-DIFFERENTIAL-E31-E32-E34_W0QQcmdZViewItemQQcategoryZ6763QQihZ013QQitemZ 230267428328QQrdZ1QQsspagenameZWDVW

where does something like this come from, seeing as it's "rebuilt" or is the gearing custom?

It's a rare puppy and nice, It will also fit!

I have one on my '91 .... its a great rear end... especially for those with a little more power then the factory provided!

-JRW

Caution!!! The front flange as shown will not fit the E31 or work with the manual transmission driveline!! It is shown as a VL-103 C/V joint flange and that is 86mm in diameter, the E31 manual transmission driveline C/V joint flange is a VL-107 and is 94mm in diameter.

It is written that the lockup is 20%, that is very light for the E31 most of the LS diffs from E32 750 are 25% lock or 80 lb/ft breakaway torque. Extra clutches he mentions must not be installed or the lock would be higher.

He does mention that the flange would have to be changed for use in a 540 but it would also have to be changed to be used in a manual transmission E31 as well.

MWrench, in tanget, would you recommend the Quaife or the M variable LSD? I currently have an ex-E32 750 3.15 25% locking unit, and was considering upgrading to either of the aforementioned.

I am curious in the pros-cons, espcially noting ease of installation, reliablity, durablity, cost, etc.

I appreciate your advice.

Caution!!! The front flange as shown will not fit the E31 or work with the manual transmission driveline!! It is shown as a VL-103 C/V joint flange and that is 86mm in diameter, the E31 manual transmission driveline C/V joint flange is a VL-107 and is 94mm in diameter.

It is written that the lockup is 20%, that is very light for the E31 most of the LS diffs from E32 750 are 25% lock or 80 lb/ft breakaway torque. Extra clutches he mentions must not be installed or the lock would be higher.

He does mention that the flange would have to be changed for use in a 540 but it would also have to be changed to be used in a manual transmission E31 as well.

Ed, how would this LSD be for an 840? Is it still appropriate? I really appreciate the wealth of knowledge you provide! Thank you.

Cheers,
Thomas

Ed, how would this LSD be for an 840? Is it still appropriate? I really appreciate the wealth of knowledge you provide! Thank you.

Cheers,
Thomas

Thomas, just to clarify, you have a 5 speed 840, correct? If so, your car will become a rocket off the line; but your RPMs will be a tad high for highway driving, at least in my opinion. On the other hand if it in fact a 4 speed car, then the RPMs will be a perfect match, IMHO, again.

Really? I was thinking that this 3.46 would be a perfect compromise between the 3.15 and the 3.91 (which I would never do). And since I was looking at a 3.64 this felt perfect, from what other 840 owners tell me is that the 3.64 LSD (if you can find it) is amazing and you would only lose about 1-2 mpg freeway driving, which to me seems reasonable? I only bring this up because I'm really torn when it comes to making decisions about my 8, and well if it comes down to it I'm just going to get a 3.15.

Really? I was thinking that this 3.46 would be a perfect compromise between the 3.15 and the 3.91 (which I would never do). And since I was looking at a 3.64 this felt perfect, from what other 840 owners tell me is that the 3.64 LSD (if you can find it) is amazing and you would only lose about 1-2 mpg freeway driving, which to me seems reasonable? I only bring this up because I'm really torn when it comes to making decisions about my 8, and well if it comes down to it I'm just going to get a 3.15.

If a 5speed car, the drivetrain is effectively the same as an E38 (in trany gearing and final drive); so from that experience, I would say much over 3.23 is getting excessive for highway cruising (which I do a lot of), especially with gas prices the way they are.

I wholeheartedly agree with your sentiments and feelings for the earlier 4 speed cars, however. They beg for a 3.46 the way 5 speed cars beg for a 3.15. :D

:'(...

I'm gonna go for 3.15 with lsd. The question is, how long will it take me to find an excellent low low mileage example...

Cheers

A very long time, it seems. I've been on the look out for just that for quite some time... I wish us the best of luck bro.

Try Bill/Chromeowner from Roadfly, He always has some hard to gets.

A very long time, it seems. I've been on the look out for just that for quite some time... I wish us the best of luck bro.


Large Case 3.15 LSD's aren't that difficult to find, just bought 2 of them a few weeks ago....

Large Case 3.15 LSD's aren't that difficult to find, just bought 2 of them a few weeks ago....

Any junk yard with a E32 750 should have one of those LSDs which may require some looking.

well, if anyone finds one or knows of one let me know! I'll go do some digging :). thanks for the info.

Cheers.

MWrench, in tanget, would you recommend the Quaife or the M variable LSD? I currently have an ex-E32 750 3.15 25% locking unit, and was considering upgrading to either of the aforementioned.

I am curious in the pros-cons, espcially noting ease of installation, reliablity, durablity, cost, etc.

I appreciate your advice.

Traditional LS diffs work well for the street applications in delivering power to both wheels in the event of loss of traction on one side, however the transfer of torque is limited by how the diff is set up, usually expressed in terms of %. Most stock BMW diffs are rated at 25% LS, for the big engine cars that translates to 80 lb/ft breakaway torque. I normally have diffs set up by Jim Blanton. He sets them up using a variable lock range from 25% to 50%. These will give you 50% lock (160 lb/ft) upon power application but backs off to 25% under neutral or power off. This is important because if you have a high lock % it will resist a turns and will make the car twitchy in severe cornering activity. For normal and spirited street driving as well as driving in limited traction conditions, a normal factory or modified factory diff should be fine.


Quaife is expensive and is used extensively in racing applications because it is very predictable, particularly cornering. It will deliver nearly a 50/50 torque split between the rear wheels under most power on applications, it reduces the coupling in coasting conditions and will allow a softer spring set up because unlike a LS diff, the Quaife unit will not cause the rear wheels to resist a pending turn. You would ba able to apply power much earlier in a turn wiothout the car becoming twitchy. One caution, if a wheel is completely unloaded, the Quaife action will immediately stop and the free wheel will break loose, once a small amount of traction is again applied to the loose wheel the quaife will begin to work.

What do you want to use the E31 for??? It is NOT going to be a slot car no matter what you do, it is heavy. As always I don't recommend what a person should do or add, but just point out that certain things will or will not help depending on the application AND the driver's needs and desires.

Would I use a Quaife? Not in an E31 but certainly in a 3 series track car.

If a 5speed car, the drivetrain is effectively the same as an E38 (in trany gearing and final drive); so from that experience, I would say much over 3.23 is getting excessive for highway cruising (which I do a lot of), especially with gas prices the way they are.

I wholeheartedly agree with your sentiments and feelings for the earlier 4 speed cars, however. They beg for a 3.46 the way 5 speed cars beg for a 3.15. :D

I think you mean the 4 speed cars beg for a 3.91, the stock 4 speed diff is already 3.64.

I also agree, with the 5 speed cars, anything higher then 3.23 will be creating a lot of unnecessary RPM at cruise. First gear will be so short, you will be in and out so fast it really doesn't do anything except make it difficult to control wheel spin. If you get to high, second gear will be the same effective ratio as 1st gear was with the stock diff.

The will be a trans fail safe issue with ratios over 3.5 ratio for the 5 speed cars. There is some comparing done with actual speed vs. tail shaft RPM, if it is excessive, the warning will get thrown.

Traditional LS diffs work well for the street applications in delivering power to both wheels in the event of loss of traction on one side, however the transfer of torque is limited by how the diff is set up, usually expressed in terms of %. Most stock BMW diffs are rated at 25% LS, for the big engine cars that translates to 80 lb/ft breakaway torque. I normally have diffs set up by Jim Blanton. He sets them up using a variable lock range from 25% to 50%. These will give you 50% lock (160 lb/ft) upon power application but backs off to 25% under neutral or power off. This is important because if you have a high lock % it will resist a turns and will make the car twitchy in severe cornering activity. For normal and spirited street driving as well as driving in limited traction conditions, a normal factory or modified factory diff should be fine.


Quaife is expensive and is used extensively in racing applications because it is very predictable, particularly cornering. It will deliver nearly a 50/50 torque split between the rear wheels under most power on applications, it reduces the coupling in coasting conditions and will allow a softer spring set up because unlike a LS diff, the Quaife unit will not cause the rear wheels to resist a pending turn. You would ba able to apply power much earlier in a turn wiothout the car becoming twitchy. One caution, if a wheel is completely unloaded, the Quaife action will immediately stop and the free wheel will break loose, once a small amount of traction is again applied to the loose wheel the quaife will begin to work.

What do you want to use the E31 for??? It is NOT going to be a slot car no matter what you do, it is heavy. As always I don't recommend what a person should do or add, but just point out that certain things will or will not help depending on the application AND the driver's needs and desires.

Would I use a Quaife? Not in an E31 but certainly in a 3 series track car.Thanks for the info! I will think about it more when/if the time comes for a rebuild.

Any junk yard with a E32 750 should have one of those LSDs which may require some looking.

Any E32 750 pre-90 (or was it 91?) that is.

USA E32 LS 3.15:1 up to 7/90 After 7/90 were 3.64 non LS ( very few 3.64 LS but some were made.)
All Euro 750s were LS 3.15.1

USA E32 LS 3.15:1 up to 7/90 After 7/90 were 3.64 non LS ( very few 3.64 LS but some were made.)
All Euro 750s were LS 3.15.1

Interesting. Was the trany itself the same pre and post 90? (ie did BMW just dial in some added acceleration from the factory :))

Same trans, just a bit more low end grunt, straight from the factory. They did the same with the 535 and 735, MB had getter acceleration numbers and this was their (BMW) way of keeping up. V-8 wasn't out yet and neither was the 5 speed.

Same trans, just a bit more low end grunt, straight from the factory. They did the same with the 535 and 735, MB had getter acceleration numbers and this was their (BMW) way of keeping up. V-8 wasn't out yet and neither was the 5 speed.

That is quite interesting. I am going to look up 0-60 times later of the early and later E32 750s and see how they compare, as well as gas mileage (for my own amusement :p)

Also, in tangent while I have your attention:

1. Is it really true there is no low coolant warning in E31s? I can't seem to find any sensor akin to the E38's...
2. http://forums.bimmerforums.com/forum/showthread.php?t=1038774

:)