3.64 lsd

[Marcp]

I really dont know what to do now.

I can get a 3.91 open and put my LSD pack into it, I just think that the M42 (well mine at least) doesnt really have the torque to lug it around with a 3.64, in some ways I like the rev happyness of the car and the twisty backroad fun you can have.   Maybe im just lazy and dont like the idea of 5th being so tall, with the 4.10 if im doing any less than 60 I need to change down to make real progress.   Cant find any vids on youtube of 318's running 3.64's.    Does the exhaust have to come off to shorten the prop for a medium case?

[tjts1]

Well I also have no PS, electric cooling fan, 22# injectors and CAI so I'm probably sending slightly more torque than stock to the wheels through the 3.64. The decision is up to you. LSDs always seem to sell well so I would go for that. If you don't like it you can always resell it. Swapping diffs from one housing to another is a complicated project.

[Marcp]

Been trying to sell this diff for ages, no one wants it (in the UK anyway)

Dunno. might just give it a go I guess, cant take too much time.

[Marcp]

Sorry to be a complete pain... but did your car "feel" any slower after you swapped?   Sometimes it doesnt matter how fast im actually going, just the car feels fast from picking up with quite a shove in 1st, 2nd gear.

Slow cornering, that sort of thing, does that mean now changing down again?   Some of the roads I go on are 2nd gear corners, to keep the car in its power zone, would I notice this too much?

Gone dizzy now... been looking at your graph too much!

Thanks for your help

[tjts1]

If you are flooring it in first and second gear and your butt dyno is very very in tune with the car, then yes, it will feel exactly 12% slower. In normal driving where you're not flooring it all the time, you'll accelerate just as quickly the car won't feel any slower. The only thing you'll notice is that the engine wont rev quite as far to get to the same speed and you'll be able to take second gear all the way past 60mph when accelerating onto the freeway.
Get really well acquainted with the procedure to swapping the diff. Theres some really good writeups on the other E30 forums. Once you're familiar with it, you'll see that its a 2 hour job the first time you do it, and a 1 hour job the second time. The whole diff is held in place with 4 bolts to the sub frame, 1 to the trunk floor, 6 allen screws to each axle and 4 bolts to the drive shaft. Its really not a big job. You might want to have a second pair to help you lift the new diff into place. If you're not happy with the diff, you can always try something else.
http://www.pelicanparts.com/bmw/techarticles/JF-Tech/BMW_E30_3_Series_Limited_Slip_Differential_Swap.htm
http://www.e30eta.com/ecdiff.htm
http://www.emotors.ca/Articles/7.aspx
good luck

[Zugunruhe]

Yup. In real world driving where you're not redlining the engine at every stop light, 3.64 diff will make for a quicker more comfortable daily driver because you wont have to shift as often. In 1st to 3rd gear you wont notice any loss of acceleration. 4th gear will feel exactly like 5th before the swap. 5th is a highway cruising gear. It will feel slower while accelerating but rpm will be about 12% lower at any speed.

Marin Pride,

I bought my Alpine White 3, 318i in spring of 2007, around the same time I think you bought a gray 318is?  Anyway, I read your diff. swap posting with interest - wanted something a bit quieter at highway speed and a little better gas mileage.  I must say it was the best mod I've done, besides completely overhauling suspension (lowering car about an inch).  With a conforti chip, the car at 180k runs like a champ and second gear to 60 if I want it.  Best of all, is fourth gear at 70 and passing with power, something I couldn't have done before.  I hope you read this, because it really is a great improvement, even if there is a bit of initial loss of power - it's more than made up for with first gear to 30....

- Dru

[Marcp]

Well I did it this weekend, fitted the 3.64.

And as far as I can tell, it drives identical to the 4.10 lol! I really have no idea what ratio this is now, im running 195 50 15 tyres, standard UK spec IS gearbox (not sure if its a different ratio to the US) and it is now doing about 65mph to 3000 RPM..... This is GPS readings, not speedo.

When I counted the crown wheel, there was 40 teeth, didnt count the pinion, cause I forgot.

Anyway... kind of wished it was a 3.64, was warming up to the idea of quiet crusing.   But my god.. isnt LSD fun?

[tjts1]

Marin Pride,

I bought my Alpine White 3, 318i in spring of 2007, around the same time I think you bought a gray 318is?  Anyway, I read your diff. swap posting with interest - wanted something a bit quieter at highway speed and a little better gas mileage.  I must say it was the best mod I've done, besides completely overhauling suspension (lowering car about an inch).  With a conforti chip, the car at 180k runs like a champ and second gear to 60 if I want it.  Best of all, is fourth gear at 70 and passing with power, something I couldn't have done before.  I hope you read this, because it really is a great improvement, even if there is a bit of initial loss of power - it's more than made up for with first gear to 30....

- Dru

That sounds like an excellent setup. I'm glad it worked out. I'm actually on the look out for a 3.73 LSD right now. My 3.64 open diff isn't cutting it anymore after my first autoX. I really think these 2 ratios are the ideal for our cars. Shoot me a PM if you're ever in San Rafael and I'll buy you a drink.
cheers
Justin

Well I did it this weekend, fitted the 3.64.

And as far as I can tell, it drives identical to the 4.10 lol! I really have no idea what ratio this is now, im running 195 50 15 tyres, standard UK spec IS gearbox (not sure if its a different ratio to the US) and it is now doing about 65mph to 3000 RPM..... This is GPS readings, not speedo.

When I counted the crown wheel, there was 40 teeth, didnt count the pinion, cause I forgot.

Anyway... kind of wished it was a 3.64, was warming up to the idea of quiet crusing.   But my god.. isnt LSD fun?

Using a quick online gear ratio calculator and the info you provided about your tire size and assuming you have the same 0.81 overdrive 5th gear, my powers of deduction tell me that you in fact have a...







Are you ready for this?





3.91 differential!


It didn't sound like you were looking to reduce RPMs for highway driving or anything like that so this might be a perfect setup for you. And yes, LSD is awesome in more ways than one
Enjoy the ride
Justin