3.46lsd to 3.64lsd worth while?

[epj3]

I'm thinking of buying an 80k mile 3.64lsd for $500 + $50 s/h (usd) from an E32 735i, to replace my current 3.46lsd. Is this a worth while upgrade from the 3.46? I'd like to do anything to get shorter gears and faster acceleration, especially on the highway. It seems most people who do this upgrade start out with a 3.46 open diff. I really don't think I want to go with the 3.91 becuase I'm not tracking the car, and still need to get a few miles per $2.33/gallon of gas. ;)

If this isn't really that worth-while of an upgrade - I'll just save myself some time and do my suspension...If I do the differential, I'll do it in the next few weeks - and then do suspension late june. If I do suspension first, I'll do the suspension mid june, so not a big difference.

So really long post short, after the $350 i can get for my current differential... is the 3.64 worth my $200?

[632 Regal]

no way man, thats way too much unless you make a lot of money to pitch into a car (I dont). that gear ratio difference wont even be noticable anyways, LSD is cool and a drug but the 'posi' has its pros if you hammer the pedel a lot and experience a lot of spin around turns and stuff.

[epj3]

no way man, thats way too much unless you make a lot of money to pitch into a car (I dont). that gear ratio difference wont even be noticable anyways, LSD is cool and a drug but the 'posi' has its pros if you hammer the pedel a lot and experience a lot of spin around turns and stuff.
I already have a limted slip. If I didn't, I would've done this swap already ;)

I'm a pro with the cons of having an lsd due to my 1988 325is. Talk about a TAIL HAPPY car.

Anyone here have a 3.91 lsd? I don't care about loosing top end, just dont want to end up with 12 mpg city and 16 mpg highway.

[niall]

i say go for it,
it will accelerate much better

[epj3]

I figure with a 3.91 it'll put the rpm's at certain speeds at around the same as my friends e36 and my former e30 (little longer than the e30 still). When I don't drive like a maniac (10% of the time...haha), I average mid 17 mpg city and around 22 - 24 mpg highway if I can keep it around 70. As long as I can keep above 15 mpg city and 20 mpg highway, I would DEFINITELY do the 3.91 swap. I dont' care about what rpm the engine is spinning at...the m30 would probably WELCOME running at higher rpm's on the highway!
//Edit: After reading bruno's site, it says the 3.91 would be a decrease of 2 - 3 mpg on the highway. Not bad - I imagine city would be more like 1 - 2 (or about the same).

If I go with this, my 3.46 lsd will be for sale!

[Jeff N.]

I'm running a 3.73 LSD from a 90 525i manual. Straight bolt in. IIR, you have to swap the flange on the 3.64 unit.

I like mine. Martin has a 3.64 unit and likes his.

I'm turning about 2800 RPMs at 70mph - up from just around 2200. I do mostly in town driving so it's not a big deal.

[bahnstormer]

no way man, thats way too much unless you make a lot of money to pitch into a car (I dont). that gear ratio difference wont even be noticable anyways, LSD is cool and a drug but the 'posi' has its pros if you hammer the pedel a lot and experience a lot of spin around turns and stuff.

wtf are u talking about? have u done this swap?
its a HUGE difference. every gear feels like a passing gear

i went from 3.46open to 3.64lsd

its worth it, come drive my car dude and u can see for yourself.

as far as what u should do, i believe in suspension tires then go fast for the
mod work

[Jon K]

wtf are u talking about? have u done this swap?
its a HUGE difference. every gear feels like a passing gear

i went from 3.46open to 3.64lsd

its worth it, come drive my car dude and u can see for yourself.

as far as what u should do, i believe in suspension tires then go fast for the
mod work


He'd get pulled over for illegal low beams

[bahnstormer]

He'd get pulled over for illegal low beams


actually its okay now
i got the one ticket, and i just carry it aroudn with me
been pulled over twice more for the lights and just wave
the ticket at em and continue my merry way ahhah
i'm invincable!

[Martin in Bellevue]

Installing the 3.64lsd was a noticeable improvement for my 535i 5 speed.
I question that $500 price, as I got one shipped for about half that from Jim at autobahn in Sandy Eggo.

[epj3]

I think I'm going with a 3.91 lsd. If it's to much of a difference (don't think it will be, sounds like it'll make the gears about as short as my e30's were, which I would love to have) I'll probably swap it out in a few more months for a 3.73 or 3.64, but I don't really mind the gas mileage decrease (I used to be concerned about gas mileage, but meh, life's too short) and like I said I don't mind shorter gears.

[632 Regal]

okay man...your right, a .064 increase must be very noticable. Thats a whopping 192 rpm increase at 3000 rpms. To take it a step farther its 320 rpms at 5k. Your tha man.


wtf are u talking about? have u done this swap?
its a HUGE difference. every gear feels like a passing gear

i went from 3.46open to 3.64lsd

its worth it, come drive my car dude and u can see for yourself.

as far as what u should do, i believe in suspension tires then go fast for the
mod work

[bahnstormer]

okay man...your right, a .064 increase must be very noticable. Thats a whopping 192 rpm increase at 3000 rpms. To take it a step farther its 320 rpms at 5k. Your tha man.


regal, what are u talking about? we are talking about drivability and feel
not how many rpms it goes up.
u have not a clue as to what u're saying and u're being an ass about it.

[632 Regal]

thats not the issue, that small of an increase would not make enough difference to feel. RPMs is exactly the thing were talking about too because thats the only change being made. I dont know what im talking about??? LMAO.


regal, what are u talking about? we are talking about drivability and feel
not how many rpms it goes up.
u have not a clue as to what u're saying and u're being an ass about it.

[Martin in Bellevue]

thats not the issue, that small of an increase would not make enough difference to feel. RPMs is exactly the thing were talking about too because thats the only change being made. I dont know what im talking about??? LMAO.

Maybe it is because we are making the changes on cars with manual transmissions, as the difference is substantial when driving around town.

Bahn, maybe we should swap in some torque convertors for a more involving drive?

[epj3]

thats not the issue, that small of an increase would not make enough difference to feel. RPMs is exactly the thing were talking about too because thats the only change being made. I dont know what im talking about??? LMAO.
But remember its not about the rpm inrease - it's about the fact that the engine doesn't have to use as much power-per-rpm to turn the wheels, so more is free'd up.

3.64 WILL be a difference, especially in a 5 speed. Look at this

Getrag 260/6

1st 3.83
2nd 2.2
3rd 1.4
4th 1.0
5th 0.81
Rev 3.46

That's the transmission ratio - are you saying that the fourth to fifth ratio difference won't do anything? Becuase that .19 ratio difference DOES make a difference, as does the .18 difference between the 3.46 and 3.64...

[bahnstormer]

Maybe it is because we are making the changes on cars with manual transmissions, as the difference is substantial when driving around town.

Bahn, maybe we should swap in some torque convertors for a more involving drive?


actually i did a diff swap in my sisters 90 535ia and went from a 3.91 to a 4.27 (iirc) and that made a difference for sure...however i wouldn't say it
is as noticeable as it is on my car.....perhaps b/c i don't drive her car enough...

a torque convertor + a flux capacitator should make our cars fly

[632 Regal]

1st 3.83 = 4.075
2nd 2.2 = 2.34
3rd 1.4 = 1.49
4th 1.0 = 1.064
5th 0.81 = 0.86
Rev 3.46 = 3.64

your thinking is not correct, the upgrade is .064 not .19, unless I really dont know what I'm talking about divide 3.64 by 3.46...I appologize if not correct here but I think I am.

I think Im real confused now.

[epj3]

1st 3.83 = 4.075
2nd 2.2 = 2.34
3rd 1.4 = 1.49
4th 1.0 = 1.064
5th 0.81 = 0.86
Rev 3.46 = 3.64

your thinking is not correct, the upgrade is .064 not .19, unless I really dont know what I'm talking about divide 3.64 by 3.46...I appologize if not correct here but I think I am.

I think Im real confused now.
The way I put it is the difference between each ratio by subtracting, not find a percentage. Either way it doesn't matter - when a bunch of people say it makes a difference - and they actually DID the mod, I have to believe them ;)

[pmlmotorsports]

The way I put it is the difference between each ratio by subtracting, not find a percentage. Either way it doesn't matter - when a bunch of people say it makes a difference - and they actually DID the mod, I have to believe them ;)
I did a 3.46 LSD - 3.91 LSD swap, BIG MISTAKE, HUGE.......way tooooooo short. a 3.64 or 3.73 is the way to go.

[Dan in NZ]

632 Regal, You're forgetting to factor in the placebo effect! "I changed the diff, it must be faster... I know it's faster... .Yes, it's much faster...".

With my pharmacology studies, we come across the placebo effect all the time... Works great, especially with those natural supplements.

[billy in slo]

Can't really use the e30 as an example though. Apples and oranges, you know. If it was not a worthwhile change BMW would not do it to extract more performance in thier M cars (and they do). Got to remember we are not cruising at 120 mph on the autobahn where the trade off in revs would be noticable. Even on the e34 Auto's BMW changed to a 4.27 from a 3.91 in mid 1990 build date. My 535A has the 3.91 but I have and will soon install a 4.27 and look forward to a noticable increase in off the line performance. HTH

[emw525E34]

Jeff,

My "95 525i Touring manual has an Open diff with 4.10 ratio. I am very surprised why the gearing was chosen as 1st gear is practically useless in the 5 speed. And 5th gear was pulling 2800 rpm at only 50 mph!. I would like to do 5th at 2800 rpm and 70 mph like yours. Would a 3.73 diff change from my 4.1 give this effect ??.

Pls advise how one would compute the rpm difference.

[billy in slo]

Jeff,

My "95 525i Touring manual has an Open diff with 4.10 ratio. I am very surprised why the gearing was chosen as 1st gear is practically useless in the 5 speed. And 5th gear was pulling 2800 rpm at only 50 mph!. I would like to do 5th at 2800 rpm and 70 mph like yours. Would a 3.73 diff change from my 4.1 give this effect ??.

Pls advise how one would compute the rpm difference.

Example: 3.64/3.46=1.05 (this becomes your multiplier)

1.05 x RPM w/orig. diff. = RPM w/new diff. in any gear at any speed.

If 50 mph=3000 RPM in 4th then 50 mph=3150 RPM in 4th (with the higher numerical diff.)

In your case you want to go the other way
3.73/4.10=.91 x 2800 = 2550 RPM in 5th at 50 mph.
(I have rounded off to the nearest hundredth in the multiplier and 50 RPM in the result for simplicity) HTH

[emw525E34]

Thanks Billy,

The difference seems much less than I expected (ie only around 300 rpm difference), does not seem much. I would want to drag first gear a lot more than 2 seconds I do now, maybe going down to 3.46 would give me the required compromise I am after. Thats almost 440 rpm deficit compared to now.