Need info

[Blueiii]

I'm considering stepping up to the DASC in the next year and a half to 2 years. Thought I'm fairly new to the BMW and autocross world, I'm fairly competent with RWD cars.

Here's the big question on my mind - can the stock differential handle almost double the stock Hp that would be produced with the addition of the DASC?? If not - what other cars will provide a direct bolt-up with similar or only slightly (no higher than 3.73) gears.

Stupid me, I bought this car to try to get out of modding the stangs - and now I'm looking at sinking even MORE in it!!! AHHHHH! I'm an addict!!

[1996 328ti]

Some say yes, I say NO.
I had a 3.45 LSD that was ready to explode.
I do about 5 driving schools a year.

The setup would be a diff from a 6-cylinder. You also will need to replace the halfshafts. Plus I'd use the M-Coupe Diff cover. Downside is the spare will note fit. I have a deflated spare with an aircompressor.

Look at the url at the top of this thread.

[Budget M3]

Originally Posted by Blueiii

Here's the big question on my mind - can the stock differential handle almost double the stock Hp that would be produced with the addition of the DASC?? If not - what other cars will provide a direct bolt-up with similar or only slightly (no higher than 3.73) gears.

I kept the stock 3.45 (open) diff when I installed the DASC about 7K miles ago (car now has 82K on the clock). I also do several driving schools and autocrosses every year. Also, for the 3 years I lived in Europe (pre-DASC) I drove the car on the autobahn at 100-110mph, sometimes for several hours at a time. I've never had a problem with the stock ti diff. I just put in good quality synthetic gear oil and keep changing it every second Inspection II...given this maintenance schedule, it should last ~200K or more...even after the power increase the DASC provides

If you really want to mod the diff on your ti, you can use just about any E30 (1984-1991 3-series) 6-cyl diff. You'll have to do new half-shafts, etc., as Steve says in his post above to make it work, though.

BTW, you'll be hard pressed to get almost double the power with the DASC (it's possible, but you'll need a lot of other mods). The DASC by itself will give you a SOLID 50% increase, though. EXAMPLE: stock hp ~140hp + 50% of 140 = ~210hp at the crank...Yippee!!!!

[1996 328ti]

I think I should restate my opinion. LSDs for a 4 banger will not last. I guess the open diff is subject to less strain.

Mark, Tarheel driving school registration is due Jan 26th!.

[J!m]

Easiest, but not cheapest, fix is to get a rear sub-frame (complete) from a six-cylinder Z3 car. Prefer 2.8, 3.0 or 3.2

If you go with the 'M' parts, you get the bonus of large brakes too. The M roadster has the finned cover already installed, so bargain shopping could net a nice package.

I would not rely on the stock ti diff for any length of time, and I think an open diff would last a few minutes longer than a LS, but why risk it?

Please see signature below...

[Budget M3]

I guess the great thing about this board (and this thread) is that everyone gets to offer their opinion. I agree that it's all just a question of money, J!m, but that doesn't mean that we all subscribe to the school that says to replace all the weak links when we upgrade our cars. Half the fun is in researching it and figuring out how to get the most bang for the buck.

I'm not a professional in the business, but there are weaker links than the diff (clutch, brakes, suspension, etc...). Sudden catastrophic diff failures are rare in my experience as a longtime enthusiast. I'll keep my stock diff until it: a) starts to whine, b) I fall into some extra $$$, or 3) I find a great deal on some MZ3 parts!

Great dialog!

[J!m]

FYI: the diff will not whine, and will fail with no warning, and at the least likely time. Just ask Ben Liaw how his failed: zero noise or other warning, pulling from a stop light easy in gear 1, no 'bang' just no forward motion.

I fully appreciate your "bang for the buck" opinion- I am from the same school. I've also been around long enough to know that if you try to cheap out, you will loose any savings you gained in a tow truck ride home when (not if) it fails. I used many used parts on my car where I could have gone new. This is how I save. I typically do a complete restoration on the individual components before instalation, replace wear parts like bushings etc. so they work and look like new, but that's just me.

By all means, use used parts. Hell, they are pre-tested for you. But if you are going to spend the time (and my time has value) and effort to do the job, it is almost ALWAYS cheaper to do it all the first time. Think about doing a clutch: you have to do all this prep work that takes many hours. I ALWAYS change the clutch disc, pressure plate, throw-out bearing, pilot bearing, pivot point, trans input seal and rear main seal. It costs a few hundred extra in parts, sure, but the job is done, and complete. I shouldn't have to divorce the tranny from the motor again for a long time. And when I do, I change everything again.

This is the way I work, and why. But the bottom line is, speed IS a question of money, and the faster you want to go, the more it will cost. You have to accept this. One way or another, and I've gone one way AND the other, you will pay the man, so I'm speaking with some first-hand knowledge on this. Steve will back me up all day long on this too, if you won't listen to me. He races, and has been there, probably many times...

Learn from me, or dont. I have (the hard way), and I'm trying to help you guys out here. I'm not going to get a cut of the parts you buy, so I have nothing to gain by this.

[1996 328ti]

I believe in paying once for things when it comes to mods.
I'm not made out of money but it is the price I need to pay to play.
I do a few driving schools a year and don't trailer the car.

I installed a Quaife. +$2600 with M coupe diff cover.
Lifetime warranty. If I was to rebuild my old 4-cylinder LSD it would have had to be rebuilt againin a couple years if I continued my track addiction. Since I don't do much of my own labor, I wanted to pay for the labor once. The diff will outlive the car.

Aluminum radiator. +$600.
I see one radiator go at almost every driving school I attend.

For the street all these things are overkill but once you get into more power you need to consider the consequence.

You are turning the car into something else you need to look at the whole picture.

FWIW- My diff gave me a warning for a year by a whirring sound. The gray metal fillings was the tip off that I had ran out of time.

[Blueiii]

Good posts and info guys!

Like I said, just trying to do my homework ahead of time. Obviously with every upgrade, something else takes extra stress, and my guess was that the diff would be the first to go. . . I had completely forgotten about the clutch.

Good lookin' out!

[Budget M3]

All good points which should be considered when seriously upgrading your powertrain. There is some "science" to this, but a certain amount of "art", too. Depending on the mileage your stock parts have, I think the weak links, in order of weakness, are as follows: clutch, guibo (flex) disc, diff, tranny...don't forget brakes, tires, and suspension, too. If you've got a low mileage car that's being modded, you can play with the order a little, but most ti's today will have >50K on the clock, so I'd guess this order is a pretty good rule of thumb.

Another big consideration, however, should be safety--if your brakes have a lot of miles or abuse (track time), then I'd replace those BEFORE doing any power mods. What good does it do to go faster if you can't stop in an emergency? Same goes for suspension--if it's weak, replace it BEFORE or at the same time as doing your power mods...same rationale...

To practice the "art" of modifying your cars, get a Playstation or Xbox with the GranTurismo game. Play with the modification menus to get a feel for what works best on different cars. The game will allow you to put 275hp in a Mazda Miata with no other mods--try driving it, however, and you'll very quickly find that you need suspension, LSD, brakes, etc. It's a cheap, fun way to learn though!

[kiley_sean]

Too bad Gran turismo doesn't have the option to do engine swaps!!! My330ti has about 20k with the stock 3.45 non-LSD. I feel that the open diff. relieve the torque alot better than the LSD. I really need to upgrade to a beefier LSD, but for guys on a budget to get the conversion up and running for daily driving, the stock small-case open diff. will hold up aslong as you don't plan on doing clutch dumps. It's the sudden surge of torque that does the most damage.



P.S. make sure and check your diff. mounting bushing, and 4 mounting bolts from time to time. I destroyed the mounting bushing, and 3 of the 4 mounting bolts backed-out on a roadtrip (I switched to an E30 M3 Diff. mount bushing from Turners &use lock-tite blue to keep the 4 bolts from buzzing out). The addition of more low-end torque will shake the shiet out of the diff. support even in modest daily driving.

[RAiMA]

Originally Posted by J!m

Easiest, but not cheapest, fix is to get a rear sub-frame (complete) from a six-cylinder Z3 car. Prefer 2.8, 3.0 or 3.2

Not sure if you're aware, but the Z3 2.8L rear ends have a wider stance. When the tires are put on, they'll definitely scrub. Trust me, I know. We've got a compact with a s/c 2.5L engine in it with the Z3 2.8L rear end with it. It just came back from the shops with front and rear flares.