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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 3 Series / 4 Series > E36 (1991 - 1999)

E36 (1991 - 1999)
The E36 chassis 3-Series BMW was a huge hit among driving enthusiasts from the first moment the car hit the pavement. The E36 won numerous awards over the years it was produced and is still a favorite of many BMW enthusiasts to this day! -- View the E36 Wiki

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  #1  
Old 09-24-2013, 12:49 PM
E36blownpast E36blownpast is offline
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Exclamation differentials

hey so i just finishing up a 302 5.0 swap into my 92 325i and i was wondering what differential i should use. its a daily driver and weekend drift car. i was lookin into the 3.91 but figured id ask since you guys probobly know more about the facts while im only good at installing and making stuff work. lol so let the suggestions begin...also axels? let me know what i need!!
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  #2  
Old 09-24-2013, 12:59 PM
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ZeGerman ZeGerman is offline
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The diff ratio is dependent on your transmission ratios, so you'll have to provide that information. As far as axles go, you'll want to use 328/M3 axles for their additional strength.
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  #3  
Old 09-24-2013, 05:02 PM
E36blownpast E36blownpast is offline
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T56
1st gear : 3.36:1
2nd gear: 2.07:1
3rd gear: 1.35:1
4th gear: 1.00.1
5th gear:0.80:1
6th gear: 3.28:1
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  #4  
Old 09-24-2013, 06:30 PM
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Jakobie1086 Jakobie1086 is offline
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Quote:
Originally Posted by E36blownpast View Post
T56
1st gear : 3.36:1
2nd gear: 2.07:1
3rd gear: 1.35:1
4th gear: 1.00.1
5th gear:0.80:1
6th gear: 3.28:1

....6th gear is almost the same as first? That's strange
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  #5  
Old 09-24-2013, 06:40 PM
E36blownpast E36blownpast is offline
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Yea i thought that too leme see if i go.that right
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  #6  
Old 09-24-2013, 06:43 PM
E36blownpast E36blownpast is offline
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correction
BA1 Ford 5.0 / 5.8 500 ft/pd torque- gears=
1st 2.97
2nd 2.07
3rd 1.43
4th 1.00
5th .80
6th .62

Last edited by E36blownpast; 09-24-2013 at 07:56 PM. Reason: missed information
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  #7  
Old 09-24-2013, 07:22 PM
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southpark11235 southpark11235 is online now
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Quote:
Originally Posted by E36blownpast View Post
nope thats right
No it is incorrect. What you are marking as 6th gear is actually reverse. Assuming the other info you gave is correct, here are your transmission's gear ratios:

1st 3.36:1
2nd 2.07:1
3rd 1.35:1
4th 1.00:1
5th 0.80:1
6th 0.62:1
reverse 3.28:1
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  #8  
Old 09-24-2013, 08:14 PM
E36blownpast E36blownpast is offline
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ok but now what differential do i wana go with?
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  #9  
Old 09-24-2013, 08:28 PM
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Quote:
Originally Posted by E36blownpast View Post
ok but now what differential do i wana go with?
How much of a "daily driver" is it? As in, will you be using the interstate a lot?

With a 3.91 I believe you'll be doing 5000 rpm at 65 mph...
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  #10  
Old 09-24-2013, 09:49 PM
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ZeGerman ZeGerman is offline
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You can use this calculator to determine your RPMs:

http://www.powerblocktv.com/resources/
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  #11  
Old 09-24-2013, 10:37 PM
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Quote:
Originally Posted by ZeGerman View Post
You can use this calculator to determine your RPMs:

http://www.powerblocktv.com/resources/
That's pretty nifty. Thanks, ZeGerman.
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  #12  
Old 09-25-2013, 08:10 AM
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ZeGerman ZeGerman is offline
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Sure thing. And if you want help determining the outside diameter of any given tire size (which is needed when using the gear ratio calculator), you can use this tire size calculator:

http://www.miata.net/garage/tirecalc.html

This one is nice to have around when shopping for tires, since it lets you see the differences between two different sizes.
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  #13  
Old 09-25-2013, 10:16 AM
E36blownpast E36blownpast is offline
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wait now im confused...how do i use this lol sorry like i said im prety much a noob when it comes to information...i just know how to put it together and make it run :/
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  #14  
Old 09-25-2013, 10:55 AM
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ZeGerman ZeGerman is offline
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Well, in order to use the gear ratio/RPM calculator, you need to enter the outside diameter of your tires, so you'll have to source that information from somewhere. The tire size calculator I posted provides you with the ability to enter your tire specs (205/60, 215/50, etc...) and obtain the outside tire diameter in inches. Take that figure and plug it into the gear ratio/RPM calculator.
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For sale: OEM E36 328 catback

Last edited by ZeGerman; 09-25-2013 at 10:59 AM.
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  #15  
Old 09-25-2013, 11:22 AM
E36blownpast E36blownpast is offline
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ok does this sound right?
speed i did 120mph (normal top speed in my opinion)
tire diameter is 23.1 inch
axel gear ratio 3.91
and i used 6th gears ratio which is .62
and i wasent sure what to use for transfer case ratio so i did 1.00

my final rpm was at 4233.03

is that correct? lol like i said i dont relly understand how to do this but if its correct than i should be able to use the 3.91 without any problem but i have a feeling im wrong lol
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  #16  
Old 09-25-2013, 11:56 AM
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What size tires are you using that have a 23.1" outside diameter? A stock tire for the 325 non-sport has an outside diameter of 24.7". A tire with an outside diameter of 23.1" would be very small, and your speedometer would be wildly inaccurate.

Also, I would base your differential gear ratio decision on the highway speed limit in your area, not a theoretical top speed (which 120mph is far too low anyway). This way, you will know what your highway cruising RPM will be, which is far more applicable to real-world conditions than top speed (unless you're building a car specifically for Bonneville Speed Week or the Texas Mile, which I doubt...).

So... Say you are running stock tires, which have an outside diameter of 24.7", your diff is a 3.91:1, and your 6th gear is a 0.62:1 overdrive. At a speed of 65mph, which I believe is your state's typical maximum highway speed limit, your engine will be spinning at 2144.37rpm.
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Last edited by ZeGerman; 09-25-2013 at 12:01 PM.
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  #17  
Old 09-26-2013, 07:53 AM
E36blownpast E36blownpast is offline
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so is that a desirable rpm to be at when going 65mph, because thats about what my jetta sits at on the freeway at 65...or do i want that 6th gear to be longer?

also what are the differential options for the e36's....with lsd
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  #18  
Old 09-26-2013, 09:54 AM
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The 3.91 is really your best choice. If you go to the 3.38 you're going to be almost bogging the engine at highway cruising speeds. The only diff with a higher ratio is the 4.04 from the 318 and I believe that is a physically smaller diff which likely isn't a good choice to be mated up with a 5.0 liter powered vehicle.

http://www.bokchoys.com/differential/GearRatios.htm
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  #19  
Old 09-26-2013, 10:14 AM
bmw-mania bmw-mania is offline
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Quote:
Originally Posted by E36blownpast View Post
hey so i just finishing up a 302 5.0 swap into my 92 325i..let me know what i need!!
It seems like you need your head adjusted for putting a 5.sl0w motor into a BMW.
Why?

Quote:
Originally Posted by E36blownpast View Post
i was wondering what differential i should use..?
its a daily driver and weekend drift car.
i was lookin into the 3.91 but figured id ask since you guys probobly know more about the facts
while im only good at installing and making stuff work.
lol so let the suggestions begin...also axels?
You're a drifter...
but, you cant be bothered to learn about what you're building.. (?)
Were you trying to EDUCATE yourself?
or just wanting a answer to your query "what differential should I use?"

Ze German gave you some great places to start.. but it seems you dont know where to begin...


Your Mustang with V8 came with 2.73 - 3.73 in the diff..
BMW's with V8 use 2.93 - 3.64 in the diff..
If you have the money.. you can pick whatever ratio you want.
(dont drifters just weld the rearend anyway?? )

If you want to make this easy..
FIND A COMPLETE BMW REAR SUBFRAME ASSY with 3.23 LSD.. (I got one if you need it)
You get the M brakes, M axles, M Diff (with LSD)
re-inforce your mounting points on your "drift" car since it IS NOT A M from the factory.
When you got the whole ass end apart for the subframe swap,
RE-inforce the mounting points for the sub-frame, and your rear Shock towers!
Unless you want the shock to blow through the wheel well in the trunk and cause you more work.
YES, it DOES HAPPEN!
You are aware of the weak spots on the standard E36 chassis, right?

Brace the hell out of your e36 if your seriously planning on Drifting it..
especially after your swap.. get the suspension dialed.
Anytime you make a adjustment... even a small one.. you have to re-check EVERYTHING.

Cheers!

EDIT:
Here is some light reading.. Enjoy..
http://forums.bimmerforums.com/forum...?t-853341.html
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Last edited by bmw-mania; 09-26-2013 at 10:27 AM.
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  #20  
Old 09-26-2013, 10:21 AM
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Aw man, now you've gone and given the recipe for the secret sauce away! I was looking forward to the future posts titled "I Ripped The Entire Rear Subframe Out of My E36" (photos included)
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  #21  
Old 09-26-2013, 10:25 AM
bmw-mania bmw-mania is offline
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^ +1

Me too!

I want to hear about the joys of "daily" driving a v8 with a 3.91..
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Last edited by bmw-mania; 09-26-2013 at 10:33 AM.
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  #22  
Old 09-26-2013, 10:45 AM
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Since he did it right and swapped in the tranny too, it should do OK as a DD. If he'd used an adapter kit and mated it up to the OEM tranny which has shorter and closer gear ratios, not so much fun, particularly with that 3.91.........

I had a friend that had an older Chevelle that was set up for the 1/4 mile and was also his daily driver. The 5.13 rear diff made it awesome on the track but it just wore you out driving it on the street with the continuous shifting required.
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  #23  
Old 09-26-2013, 10:49 AM
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Quote:
Originally Posted by bmw-mania View Post
It seems like you need your head adjusted for putting a 5.sl0w motor into a BMW.
Why?
I believe it is you need your head adjusted. American car manufacturers have always been good at one thing, and that’s POWER. Why wouldn’t you want to take a firebreathing V8 and put it in a car that can actually take a corner well? It is the perfect combination, taking the best aspects from both cars to create a monster in the straight and the corners.


OP, just like in your last swap thread, I approve this swap.
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Old 09-26-2013, 11:10 AM
bmw-mania bmw-mania is offline
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Originally Posted by southpark11235 View Post
I believe it is you need your head adjusted. American car manufacturers have always been good at one thing, and that's POWER.
Yes... Ammuuurricakkannannns have been putting big motors in small cars for damn near a century.
Its a pretty simple concept.. one simple people cant get out of.

The "illusion" of "POWER" as you put it... is a seductive b!tch

Quote:
Originally Posted by southpark11235 View Post
Why wouldn't you want to take a firebreathing V8 and put it in a car that can actually take a corner well? It is the perfect combination, taking the best aspects from both cars to create a monster in the straight and the corners.
Yes, these E36's handle GREAT.
But, when you shoehorn a V8 into a E36 you unsettle the vehicle.

The NOSE of the car is now HEAVIER than before..
which compromises that great HANDLING we both have grown to love.
Not exactly a "perfect" combination, or the "best of both worlds"..

"firebreathing"
.. Its a solid engine for predictable linear power output.
You may have something cute for the straight lines.. but the corners will kill.
(read: physics)

Why even V8? Why no boost? Hell.... WHY NO WERK on MOTOR?

Quote:
Originally Posted by southpark11235 View Post
OP, just like in your last swap thread, I approve this swap.
FORM & FUNCTION.. not just cutesy coon-tail builds.


PS-- have amber corner lights.. want?
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Last edited by bmw-mania; 09-26-2013 at 11:13 AM.
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  #25  
Old 09-26-2013, 11:30 AM
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Quote:
Originally Posted by bmw-mania View Post
Yes, these E36's handle GREAT.
But, when you shoehorn a V8 into a E36 you unsettle the vehicle.

The NOSE of the car is now HEAVIER than before..
which compromises that great HANDLING we both have grown to love.
Not exactly a "perfect" combination, or the "best of both worlds"..

"firebreathing"
.. Its a solid engine for predictable linear power output.
You may have something cute for the straight lines.. but the corners will kill.
(read: physics)
302 = 460 lbs
m52 = 436 lbs
302 with aluminum heads = 416 lbs

If you use aluminium heads you are actually losing weight, which nullifies your whole handling argument.
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