View Full Version : 3.45 vs 3.73 LSD
Well the power im looking for is not all power off the line, and not all the power in high end. Id like to be somewhere in between just of coarse the tires gripping to the ground and both tires spinning together. I like the feel of how the car feels stock alone right now. So i heard that the 3.73 are shorter gears and all the power off the line but high end sucks? Anyway, what would be a good LSD where im in the middle. Dusten told me 3.45. Just wondering, what is the difference that im going to feel driving with nothing now, and when putting the 3.45 LSD?
I would like to know how/what/and where to find the right one thats just bolts in without modification or major modifcation. I get confused cuz i hear you guys say you guys get LSD's from e30's and what not.
TIA.
pnosker
09-30-2006, 12:09 AM
3.45 LSD was what came with the 318ti as an option, afaik.
Tyler
09-30-2006, 12:36 AM
3.73 gears would be fine in the car,you won't lose to much high end power. The question you have to ask yourself is with the kind of driving you do what suits you best. If you rarely drive on the highway then who cares about the power at high speeds. For instance my friend is putting 4.10 gears in his car cause he wants the low end performace. He hardly ever drives on the highway and he just wants to get beteer 1/4 mile times. With 4.10 gears 1st gear really does nothing for you ,it's 2nd 3rd & 4th that has the power. Most people who want the low end performance that put in 3.73 gears wish they bought the 4.10 and it's not a cheap part to buy and install.
So basically pick whats best for you depending on how you drive your car.
im on highway just as much in street.
Tyler
09-30-2006, 01:03 AM
im on highway just as much in street.
Then you would probally want 3.73 or one step below that.
Then you would probally want 3.73 or one step below that.
What exactly is the 3.45? Wheres the power at?
Panzer_M
09-30-2006, 01:10 AM
3.46 or 3.64 are you best bets with a large diff
if you want to keep the small diff, then the 3.45LS is it..I love mine vs the open I had in the 97 Ti.
the most power is in 3rd it feels with the .45, but I lost some low end torq with my LTW flywheel. 1st gear is there but weaker, 2nd is the pickup and 3rd-4th are my driving gears, and 5th is for cruising but has some response but not enough power as I would like to have on hand.
Budget M3
09-30-2006, 05:53 AM
Understand the whole street vs. track consideration...it's a tough call for a vehicle that will also be used on the highway. I would recommend staying with stock ratio of 3.45 if freeway comfort is part of your vocabulary.
My dilemma: Mainly street use at 55mph or less...occasional freeway use at 75-80mph but only to drive the two hours to my "local" track. I see 115mph in 4th gear before I both hit the rev limiter and have to hit the brakes at the end of a long straight at the track, so the 3.45 seems just about right. I sure would like a little extra jump on the low end, though, so am considering a switch to 3.73. Anyone know what the top speed is at 6500rpm in 4th and 5th gear for a 3.73? Better yet, top speed in all gears 1st-5th?
eeeehh i dont know. Maybe i just wont put any LSD. To complicated.
L84THSKY
09-30-2006, 01:16 PM
Get the E28 3.46 LSD. Drops right in, no mods and uses the original flanges and halfshafts.
eeeehh i dont know. Maybe i just wont put any LSD. To complicated.
what does the 3.46 do? As in power driving or whatever the difference would be of having a 3.45 lsd and not having a lsd since u have one.
L84THSKY
09-30-2006, 06:40 PM
Same ratio as you already have, but stronger diff and possi traction.
I spent the last 2 years building up my car to enhance all key areas. The last thing I will do, is drop the supercharger in. You better consider the consequences of putting in the DASC with a totally stock car.
what does the 3.46 do? As in power driving or whatever the difference would be of having a 3.45 lsd and not having a lsd since u have one.
Panzer_M
09-30-2006, 07:06 PM
na, let him do it. It will be fun to hear the stories.
L84THSKY
10-01-2006, 04:32 AM
Braking, Suspension, Transmission and Final drive deficiencies. But hey, atleast we can see what effect a DASC has on a stock car. It will be helpful for others to find out what areas would need improvement, by seeing what fails on your car.
Consequence? Like...?
well when i read up on there site, it didnt say anything about having or needing to upgrade anything. But hey, if something were to happen, how would u guys know?
Budget M3
10-01-2006, 08:21 PM
Sorry to (slightly) hijack this thread, but I have to disagree guys...There are always two sides to the story. DASC on a stock car that is in good condition, is a very reasonable upgrade by itself and does not REQUIRE any other upgrades at the same time. Yes, the extra power of the DASC will uncover weaknesses elsewhere in the drivetrain, but the effect will be gradual and over time. Here is my story...
1. It is important that the rest of the vehicle be in good condition to start with. Engine compression and tune should be impeccable. If yours is not, then spend money here first. I popped in the DASC on a stock car with 75K miles....then:
2. My first upgrade after that was springs, shocks and tires about 5K after that (not really necessary, but makes it a lot easier to take advantage of the extra power--and have much more fun!)
3. At ~85K, I replaced the clutch. The clutch is the weakest link on the stock car once you add the extra power of the DASC. The clutch, however, will not fail catastrophically without advanced notice. When yours starts to slip, it's time to replace it. The only exception here would be if you are going to drag race or drift...in that case, you might want to save the hassle and do the clutch at the same time.
4. At ~90K, I upgraded the brakes to vented rotors. After a few track events, the solid rotors on the stock car got easily warped with the extra speed on the track. Stopping power is about the same (which is extremely good), but rotor longevity and lack of fade make this a good upgrade for the track.
5. I am now looking for a LS differential, but not because the stock unit is failing (it will also make itself known in advance if it is being overwhelmed by the extra power). Some people have reported catastrophic failures of their diff without warning, but I believe that is rare. My stock diff is just fine, but I want to add LS for extra performance on the track.
So, unless you plan to drop the clutch and spin the tires a lot, DASC on an otherwise stock car is a very reasonable upgrade, even if you drive the car hard. If your budget would require, it might be prudent to begin setting aside some cash for the clutch and diff, but you should have plenty of advance notice when those will NEED replacement.
aceyx
10-01-2006, 08:32 PM
There is no explicit need to change anything. But car manufacturers don't just slap a motor to a frame then wrap it in sheet metal, they have to engineer all the systems to work together.
When you change something (add power), you have to look at other areas, such as braking, additional stress on drivetrain parts from the power, etc.
Adding the DASC is like adding a monster subwoofer to your car, without looking at amplifiers, capacitors, head unit and other speakers. Sure you may have increased bass response but now everything else is lacking.
My clutch is new. It was replaced when i put the new replacement engine in. Let says after a while it starts loosing it, what kind of clutch should i go with?
About the LSD, im not to worried about it. If i find a cheap price one, maybe ill go for it.
Budget M3
10-01-2006, 09:05 PM
My clutch is new. It was replaced when i put the new replacement engine in. Let says after a while it starts loosing it, what kind of clutch should i go with?
It's complete overkill, but I replaced mine with an M5 clutch (>400 ft-lbs of clamping power...way more than you need for the ti with DASC). Reason I went for the M5 unit is that I also replaced the flywheel while I was in there with a lighter unit. Although more expensive for the part, the M5 clutch was an easier job (less labor) than an E36 M3 clutch when also changing the flywheel. An M3 clutch will also work though. IIRC, the M3 clutch required some modifications to fit in the ti...
Budget M3
10-01-2006, 09:16 PM
There is no explicit need to change anything. But car manufacturers don't just slap a motor to a frame then wrap it in sheet metal, they have to engineer all the systems to work together.
Adding the DASC is like adding a monster subwoofer to your car, without looking at amplifiers, capacitors, head unit and other speakers. Sure you may have increased bass response but now everything else is lacking.
True...However, my experience is that the ti is overengineered for the puny M42/M44 engine to begin with, so it's more easily upgraded in stages relying on the stock parts until they wear out from the extra stress.
Re: subwoofer analogy...LOL Does this mean I can't fill my trunk with speakers to make it go faster? ;-) LOL I have found that adding a SMALL subwoofer, however, will make even the stock stereo sound remarkable better...
Panzer_M
10-01-2006, 10:32 PM
It's complete overkill, but I replaced mine with an M5 clutch (>400 ft-lbs of clamping power...way more than you need for the ti with DASC). Reason I went for the M5 unit is that I also replaced the flywheel while I was in there with a lighter unit. Although more expensive for the part, the M5 clutch was an easier job (less labor) than an E36 M3 clutch when also changing the flywheel. An M3 clutch will also work though. IIRC, the M3 clutch required some modifications to fit in the ti...
UUC Stage II w/ DASC?
How is that? Track events yet?
L84THSKY
10-02-2006, 12:58 PM
I hate to say this, but it sounds like you are contradicting yourself. You said nothing needs to be replaced, but then you started to replace everything. The point is, the car was engineered without supercharging. Make sure all other areas of the car are up to the challenge, now and for the future. Replacing failed or worn out parts as they happen is backwards engineering.
Sorry to (slightly) hijack this thread, but I have to disagree guys...There are always two sides to the story. DASC on a stock car that is in good condition, is a very reasonable upgrade by itself and does not REQUIRE any other upgrades at the same time. Yes, the extra power of the DASC will uncover weaknesses elsewhere in the drivetrain, but the effect will be gradual and over time. Here is my story...
1. It is important that the rest of the vehicle be in good condition to start with. Engine compression and tune should be impeccable. If yours is not, then spend money here first. I popped in the DASC on a stock car with 75K miles....then:
2. My first upgrade after that was springs, shocks and tires about 5K after that (not really necessary, but makes it a lot easier to take advantage of the extra power--and have much more fun!)
3. At ~85K, I replaced the clutch. The clutch is the weakest link on the stock car once you add the extra power of the DASC. The clutch, however, will not fail catastrophically without advanced notice. When yours starts to slip, it's time to replace it. The only exception here would be if you are going to drag race or drift...in that case, you might want to save the hassle and do the clutch at the same time.
4. At ~90K, I upgraded the brakes to vented rotors. After a few track events, the solid rotors on the stock car got easily warped with the extra speed on the track. Stopping power is about the same (which is extremely good), but rotor longevity and lack of fade make this a good upgrade for the track.
5. I am now looking for a LS differential, but not because the stock unit is failing (it will also make itself known in advance if it is being overwhelmed by the extra power). Some people have reported catastrophic failures of their diff without warning, but I believe that is rare. My stock diff is just fine, but I want to add LS for extra performance on the track.
So, unless you plan to drop the clutch and spin the tires a lot, DASC on an otherwise stock car is a very reasonable upgrade, even if you drive the car hard. If your budget would require, it might be prudent to begin setting aside some cash for the clutch and diff, but you should have plenty of advance notice when those will NEED replacement.
DustenT
10-02-2006, 01:29 PM
I ran my DASC completely stock (including stock Automatic transmission) with zero problems. I combined preventive maintenance and upgrading together and ended up where I am now. I bought almost all of my performance parts used (tranny, LSD, springs, bilsteins, sways, SSK, etc...) to save money and it ended up being cheaper t0 modify the car than to replace with factory parts.
You don't need anything extra, but with the extra power you re-learn to love your car again and want to make it awesome(er).
As far as the differential goes.... I run close to 4k rpms on the highway at 80-85mph. There is NO way that I would recommend anything shorter than a 3.45. Remember, the DASC adds LOTS of low end, so running something taller isn't all bad.
campaiar
10-02-2006, 01:50 PM
I'm with DuntenT here. I'm running a 3.64 LSD rear end, and I'm at 4100 rpms at 80 mph. Not a fan.
I drove down to Louisville this weekend and kept it around 70 so I didn't have to listen to the motor rev. While it is extremely quick through the gears, I'd trade it for lower highway rpms.
so from what model should i get the 3.45 lsd from? Where i could just bolt it right on? So ok i hear that 3.73 are short gearing, but i didnt hear anything about 3.45?
DustenT
10-02-2006, 06:21 PM
so from what model should i get the 3.45 lsd from? Where i could just bolt it right on? So ok i hear that 3.73 are short gearing, but i didnt hear anything about 3.45?
You have a 3.45 right now. What do you think of it? A direct sway would be from a 1995 Club Sport. I paid $400 for one with 80k miles on it, and it sounds like that's a steal compared to what some people are paying.
I expect the diff to break on me, they aren't designed to handle the kind of abuse I give it so I would be heart broken when it explodes. Wait until you have the DASC installed before you buy any more parts.
So its a 3.45 open differential? So the LSD would just make both tires work together so i will pretty much feel the same feeling huh.
PS. you still havent told me anything about the check valve :frown:
DustenT
10-02-2006, 06:49 PM
So its a 3.45 open differential? So the LSD would just make both tires work together so i will pretty much feel the same feeling huh.
PS. you still havent told me anything about the check valve :frown:
Yes, the 3.45 open feels the same as the 3.45 LSD, except when the wheels spin.
What do you want me to do about the damn check valve??? If they don't sell it, they don't sell it, seems pretty straight forward to me. Looks like you'll have to wait for someone to sell a used one.
If they don't sell it, they don't sell it, seems pretty straight forward to me. Looks like you'll have to wait for someone to sell a used one.
LOL! i didnt ask you to make them sell it. I asked if you knew of another website or anywhere else where they sell it or i can locate it.
JedzE36/5
10-03-2006, 04:14 AM
my buddies S52ti with 3.73 tops out at about 145ish i believe (or he just stops pushing it at about that speed). for highway driving he is at about 5k at ~75mph. its not too horrible but if your car is gutted out and you are running no cats then it can be a pain. for a combination of street/highway i would recommend a 3.73. the acceleration from the entire power band is crazy. my 3.45 M52 ti is neck and neck in 1st gear with a modded M42 ti with a 3.73 all from the gearing. after that my hp kicks in.
keep in mind that 1st gear will be basically useless with the stock 4 cylinder tranny because of the shorter 1st and 2nd gears compared to the 6 cylinder tranny. but that could just be on DASC and 6 cylinder tis.
I dont think ill be putting one in. To complicated to much hasle.
JedzE36/5
10-03-2006, 04:24 AM
it actually isnt too bad. i think the only hard part w/the 3.73 is that you will have to source E30 output shafts since your stock ones wont work. its a worth while upgrade though especially if you are going to have more power. the stock output shafts are noodles with any meaningful power.
keep in mind that 1st gear will be basically useless with the stock 4 cylinder tranny because of the shorter 1st and 2nd gears compared to the 6 cylinder tranny. but that could just be on DASC and 6 cylinder tis.
The gear ratios on the ti and M3 transmissions are the same for all five gears.
Panzer_M
10-04-2006, 06:31 PM
why does the 3.64 use/can use the stock Ti shafts w/o problems, but the 3.73 needs e30 shafts? Both have the same case, or else the M coupe diff cover wouldn't work for both the 3.73 and 3.64...or am I missing something here?
Wait..is it the flanges that make the differance in shafts?...just thought of that..duh.
L84THSKY
10-05-2006, 07:10 PM
I can tell you this. When I had the E28 LSD with the stock flanges and halfshafts, the shafts were very tight going in. When I recently swapped the stock flanges and halfshafts, the E30 shafts mated with the E30 flanges very nicely.
why does the 3.64 use/can use the stock Ti shafts w/o problems, but the 3.73 needs e30 shafts? Both have the same case, or else the M coupe diff cover wouldn't work for both the 3.73 and 3.64...or am I missing something here?
Wait..is it the flanges that make the differance in shafts?...just thought of that..duh.
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