LSD 4.27 Diff, Questions

[deekay]

something not mentioned yet in this thread is that several non-M 6-cyl Z3s came with torsen (not clutch-pack) LSDs.

i swapped my 4.10 med-case clutch-pack out for a 4.10 torsen from an auto Z3 a few months ago and i love it. it just knows where the grip is, and in the wet where a clutch-type would just spin both wheels, i can feel the ass end of the car wiggle ever so slightly as it sends power to whichever wheel has more traction. they also don't wear out like a clutch-type does. (well, they will eventually, but the diff is likely to outlive most of the rest of the car.)

i'm pretty sure they were available in 3.73 also, and if i had an e36 m42 car, that's the ratio i'd look for.

as a side note, US-spec 318i convertibles came with a 4.27 open small-case. i still have the one that came out of my car, if anyone wants it.

[92BMW318is]

i have a question again..  

I just bought a diff from pull a part, it came off a 93 325i same exact diff case, even asked the ladie she said it was interchangeable. so i go out there take the Diff off the 325i. So i get back and take my old diff off and put the 325i on my 318is, everything fit well, nothing went wrong.

until i drove it and it has a lower gear ratio, it seems. at 65mph Im buried at 4rpm. with the old one i was close to 3rpm at 65mph.

What i dont get is the engine in the 325i was the same engine as mine,
same engine block, same intake, the only thing i seen that was differnt was the fuel injectors which i took, want to know if the fuel injectors for the 325i will work with my car.

but the biggest thing i want to know is why there is such a big difference in rpms, i thought the guy that use to own the 325i had some 17inch rims or somthing. is there a difference if the car was automatic or Manuel?
ha if i did go and buy some bigger wheels would this lower the rpms?
Also is 65 at 4rpms bad for my engine, i dont want to blow my motor

thanks for your help

[Warsteiner]

Dude,
You have major conflicting information so it makes it very hard to give you the correct advice.

E36              
325i/is  1992/93    3.15 (M)    3.15 (M)     3.19 (A)    3.19 (A)    
318i/is  1992/93    3.45 (M)    3.45 (M)     4.45 (A)    
325ic    1994   3.15 (M) 3.64 (A)

                              
Those are the ratios available.  You don't have a lower gear ratio in your car now, you have a higher one. Higher ratio has quicker pick up which makes you run out of gear faster which makes you run higher RPM.

Clearly the 318 ratios are higher than the 325's. This would mean that you have a completely different diff in your car NOW that you have no idea what it is, OR you didn't have the correct diff in your car to begin with:-) What if the junker car's previous owner was an enthusiast and changed the diff?

Just as an example with tire change, you can take a 4.10 and switch from a 225/50 tire to a 225/45 and it will effectively change your diff to a 4.17

Do you have a 318 or a 325?  You said the 325 junker has the same motor, engine block and intake as your car which means you don't have a 318 unless you or someone else did a motor swap on your car.  

Let's start with do you have a 4cyl or a 6cyl?

How many fuel inj's did you take from the junker? And how many do you need for your car?

What does the lady at this place really know? Yeah the "size" of the case may fit but not the ratio. Something is a miss and it's hard to help if all the info is not complete and correct.

I would not run a diff that put me at 4K @ 65mph. It will shorten the life of the motor.  It won't blow up but I think that it's way too high of a ratio that you have now.

~Ralph

[DesktopDave]

Keep in mind that auto trannys & manual trannys carry different diff ratios too.  and a 'vert will always have a much lower (bigger number) diff because it's hundreds of pounds heavier than the hardtops.  You can look for a metal tag on the diff case that will have the ratio stamped on it.  The cases can all swap easily, but the ratio might be totally wrong for your car.

The diff and the wheels will combine to produce your final drive ratio...so say you have a 4.10 - the diff divides the driveshaft revs (not the engine RPM) by 4+, then the wheels multiply each rev by their circumference to get mileage.  So the smaller the tires, the faster the car will run.  It's a lot of math, but it's not hard to do.

Don't worry about 4k RPM...I run mine there often.  It'll shorten the engine life if you do it all the time though.  I'm pretty sure the injectors are physically the same but can vary on flow rate.  There are a few detail differences but they're all Bosch designs. You'll have to check the part numbers to be sure how much fuel they flow.  Going to slightly larger injectors usually helps with idle and might give you a few more HP.

[92BMW318is]

Keep in mind that auto trannys & manual trannys carry different diff ratios too.  and a 'vert will always have a much lower (bigger number) diff because it's hundreds of pounds heavier than the hardtops.  You can look for a metal tag on the diff case that will have the ratio stamped on it.  The cases can all swap easily, but the ratio might be totally wrong for your car.

The diff and the wheels will combine to produce your final drive ratio...so say you have a 4.10 - the diff divides the driveshaft revs (not the engine RPM) by 4+, then the wheels multiply each rev by their circumference to get mileage.  So the smaller the tires, the faster the car will run.  It's a lot of math, but it's not hard to do.

Don't worry about 4k RPM...I run mine there often.  It'll shorten the engine life if you do it all the time though.  I'm pretty sure the injectors are physically the same but can vary on flow rate.  There are a few detail differences but they're all Bosch designs. You'll have to check the part numbers to be sure how much fuel they flow.  Going to slightly larger injectors usually helps with idle and might give you a few more HP.

so is there anyway to fix the ratio, like going up tire sizes,

how hard is it to change out the guts?

also the whole tranny was taken out of the car i took the diff off of it looked like it it might of been a Manuel but the clutch wasn't there ither

also the person asked me if the diff i had was a locking differential. im sure it isnt but, whats the diffrence

[DesktopDave]

The easiest way to change the ratio is to find the right diff and swap it in.  Changing wheels and tires can be another way to change the effective ratio.

You could change out the ring & pinion gears and even bolt a limited-slip pack into an open diff, but it's always cheaper to buy a used unit.  A mechanic needs to set the front flange pre-load properly, or the diff will burn itself up quickly.

BMWs can be tail-happy, so they sometimes come with "locking" or "limited-slip" (LSD) diffs.  They usually have a big "S" painted on the case.  The opposite of an LSD is an "open" diff.  A quick way to check is to spin one of the wheels or output flanges and see which way the other one goes.  If it spins the opposite direction, you have an open diff.  If it spins the same way, you have an LSD.  They're also usually about twice as expensive as the open units.

[92BMW318is]

Dude,
You have major conflicting information so it makes it very hard to give you the correct advice.

E36              
325i/is  1992/93    3.15 (M)    3.15 (M)     3.19 (A)    3.19 (A)    
318i/is  1992/93    3.45 (M)    3.45 (M)     4.45 (A)    
325ic    1994   3.15 (M) 3.64 (A)

                              
Those are the ratios available.  You don't have a lower gear ratio in your car now, you have a higher one. Higher ratio has quicker pick up which makes you run out of gear faster which makes you run higher RPM.

Clearly the 318 ratios are higher than the 325's. This would mean that you have a completely different diff in your car NOW that you have no idea what it is, OR you didn't have the correct diff in your car to begin with:-) What if the junker car's previous owner was an enthusiast and changed the diff?

Just as an example with tire change, you can take a 4.10 and switch from a 225/50 tire to a 225/45 and it will effectively change your diff to a 4.17

Do you have a 318 or a 325?  You said the 325 junker has the same motor, engine block and intake as your car which means you don't have a 318 unless you or someone else did a motor swap on your car.  

Let's start with do you have a 4cyl or a 6cyl?

How many fuel inj's did you take from the junker? And how many do you need for your car?

What does the lady at this place really know? Yeah the "size" of the case may fit but not the ratio. Something is a miss and it's hard to help if all the info is not complete and correct.

I would not run a diff that put me at 4K @ 65mph. It will shorten the life of the motor.  It won't blow up but I think that it's way too high of a ratio that you have now.

~Ralph

i have a 4cylinder 318is the 325i had a 4cylinder, i got 4 injectors from it from it. a ICV and a bumber strip. the 325i at the yard had the same intake the same fuel rail the same engine the same throttle body, ect.. i looked up the 325i motor yesterday i couldnt find anything that said they made 4cylinders which is confusing me.

so same motor same body e36... i dont see why the diff would be geared so diffrently if the 325i has a lower gear ratio like you stated then my car shouldnt be running at high rpms, unless the diff was swaped into the 325i before it was scrapped.

[deekay]

you have not made this any less confusing

only explanation i have is that the j-yard car was a 318i/s rebadged as a 325i, because every e36 other than the 318i/s had a 6-cylinder.

btw i just drove from sacramento to LA... i'm at 4000rpm right at 80mph and i sustained that speed the whole way. if you usually cruise at 65, i wouldn't be that worried about sustaining that RPM continuously. my vote is change your oil frequently, enjoy that quick acceleration, and get some other modifications to accentuate it.

[92BMW318is]

you have not made this any less confusing

only explanation i have is that the j-yard car was a 318i/s rebadged as a 325i, because every e36 other than the 318i/s had a 6-cylinder.

btw i just drove from sacramento to LA... i'm at 4000rpm right at 80mph and i sustained that speed the whole way. if you usually cruise at 65, i wouldn't be that worried about sustaining that RPM continuously. my vote is change your oil frequently, enjoy that quick acceleration, and get some other modifications to accentuate it.

im reallllllly sorry guys but it came off of a 320i not a 325i :/

so i guess the diff i have is a 2.73.... :/

[PumpItUp]

stop doing drugs. then work on your car or post on this forum

[Warsteiner]

deekay and PumpItUp are both right, but PumpItUp takes the cake on this one!!  

You have no clue what the hell you're talking about.  If you did then you wouldn't have made such a ridiculous statement.

Now I know you're wasting everyone's time here. Go read and learn about what you think you might have and might fit and then get back to us with an educated, sensible, logical, and realistic view point that really needs attention.

~Ralph

im reallllllly sorry guys but it came off of a 320i not a 325i :/

so i guess the diff i have is a 2.73.... :/

[deekay]

yup, e36 320i is still an inline-6 car.

as has been said, what you have in the car now is a numerically high diff if you're turning 4Krpm @ 65mph- it HAS TO be something 3.73 or above.

come to think of it, i think i am turning about that much rpm @ that speed in 4th gear (1:1), so you may very well have found a 4:10. who knows.

either way there should be a tag on the rear cover of the differential that says the ratio and can end all of this conjecture immediately.

at the end of the day you've got a nice short-geared setup that's well suited to the peaky little 4-banger under your hood, and you said you wanted acceleration at the expense of top-speed. now you've got it. stop worrying about it and start researching what suspension and tires you might want.

[Warsteiner]

Yes the 320i is a 6cyl (my cousin has one in Germany) but was not imported to the USA. However, 3 cars were donated to the Georgia State Police in 1996 for the Olympics in Atlanta and were tagged "1" "2" and "3" on the license plates. After the games they were put into regular service for patrol. 2 were hit and crashed (not by the officers) and not sure what happened to "3".

MPH= (RPM)(TIRE DIAMETER in inches) [divided by] (GEAR RATIO)(336)

Now  92BMW318is can go figure it out for real.

~Ralph

[92BMW318is]

Yes the 320i is a 6cyl (my cousin has one in Germany) but was not imported to the USA. However, 3 cars were donated to the Georgia State Police in 1996 for the Olympics in Atlanta and were tagged "1" "2" and "3" on the license plates. After the games they were put into regular service for patrol. 2 were hit and crashed (not by the officers) and not sure what happened to "3".

MPH= (RPM)(TIRE DIAMETER in inches) [divided by] (GEAR RATIO)(336)

Now  92BMW318is can go figure it out for real.

~Ralph

I dont know what to tell you guys, the fucken 320i had a 4 cylinder same exact setup as mine, engine wise.

my bad i said it was a 325i.

i dont do drugs.

if bmw didn't make the 320i in a 4 cylinder then why are they selling them online.
   http://market.autopartsfair.com/used-parts-leads/bmw-320i-air_conditioner_compressor-request-1272319.html

[deekay]

i think we're all done arguing with you. good luck.