4.44 open to 4.10 LSD question

[wv318ti]

I don't post here much but love to read and learned a lot from this wonderful site. I don't understand differential ratios well, and can't research much due to searching on an iPhone. I own a 98 that's been supercharged and the current back end can't take the torque well. I just reciently picked up a 4.10 LSD off an 88 325i for 200 from a junk yard. My car is unfortunately an automatic with an open 4.44. What will this change do to my rpm's at 80 mph, and will it accelerate faster or slower due to the ratio change?

[FMD]

It will reduce your rpms at 80mph, if at 80mph you were running at 5000rpm, it will be reduced to 4600rpm.

You will accelerate slower also.

[spykejones]

Are you switching from a 4.44 to 4.10 lsd because you cant find a 4.44 lsd or to lower the RPM's.

I just had to buy a 4.44 lsd for my busted assed automatic all to find a standard 318ti in better shape then my automatic that I plan to drive instead. A 4.44 lsd is hard to find that is for sure. I found my 4.44 LSD after looking for a month online. Luckily it was about 100 miles away from my house and it only had 35,000 miles on it. I plan to sell the Diff because now I have a manual and it is 3.45 not sure if it is LSD or not yet (I haven't had time to get under it and spin the wheels to see if they move in the same direction).

Just wondering what the reason for the 4.10 lsd was.

[spykejones]

I lived in Athens, Ohio for 20 years and you arent that far from my parents house. I live in Columbus now. If you would be interested in it let me know.

[wv318ti]

I could probably meet up with you somewhere in Athens if that's what your trying to say. Or any other place that would be about half way.

[spykejones]

I paid $400. (including tax for this diff and it is in great shape, It has fresh gear oil in it from when I installed it. I could let it go for $350. IF you pick it up in Athens that would be half way and I can visit family members so it would work out. If you would be interested. Let me know. If you arent interested I will put it on craig$li$t as well as listing it here and some other sites. All the other ones I found are in Alabama and not many were LSD. Get while you can. I am not interested in making a profit just getting most of my money back to put toward a 3.45 LSD. Also I have not put a single mile on this diff since I bought it simply because my auto doesn't run because of EWS needs aligned and I have a standard so I am parting the Auto out. Let me know if you want or need anything. Thanks

[Mad-Machine]

um... you guys are getting the ratios backwards. a 4.10 ratio rear is going to spin SLOWER than than a 4.40.

Basically.. for ever turn of the axle.. the driveshaft will turn 4.4 turns with a 4.40.. 4.1 turns for a 4.10... the higher the ratio, the more torque you can put down and the faster your car will accelerate.. and the faster you will run out of revs when you try and do a highspeed run

[wv318ti]

Thanks I know what I've got now, it's why I had posted here to ask about it. I don't know why he's trying to sell another to me. The way he posted the first time I thought he wanted to meet up to check out Cars

[spykejones]

wow man I was just out to help. I just thought that if you were swapping from a stock ratio to different ratio to get LSD because you might not have been able find a stock 4.44 lsd. I plan on putting a listing in the FS forums. I would like to meet sometime to talk cars. I just have some bodywork to do before I can drive it. Sorry for the mixup

[briansol]

right, 4.10 is LONGER than a 4.44.

as an example:

if you could do 80 in 3rd on the 4.44, you'll likely top out 3rd at 90 on the 4.10, and it will take you longer to get there.

[Dusty_Hale]

Yes, with the 4.40 Gear ratio, the rear end will allow for a faster rate of acceleration, versus the 4.10. The drawback to the 4.40 ratio is that your RPMs will stay up even while you're in Overdrive. Other things to consider are the drive ratios from first through fifth, fourth being the final drive ratio, and fifth being overdrive. You should match the gears in the rear end to the gears in the transmission. Also, you might run into the problem of your speedo being off by a few miles per hour, unless you change the speedo gear. If your speedo is computer controled based off of VSS sensors, then you wouldn't have to worry too much. You could fix that with a flash tuner.

So, the new question is this: Do you wanna save gas, or do you wanna have a balls out acceleration machine?

[Mad-Machine]

speedo is run off of the diff. He should have NO issues with the speedo being off with just a ratio change

[Dusty_Hale]

Originally Posted by Mad-Machine

speedo is run off of the diff. He should have NO issues with the speedo being off with just a ratio change

Exactly my point. The Speedo is run off of the diff. If you change the ratio so that it spins faster, you would need a speedo gear that is calibrated to that ratio, right? I've run into that problem before with changing the rear end gear ratio in many cars. We usually had to re-flash the ECU to compensate for the difference. And that didn't even work all the time. But, I've never done this in a BMW before, so, I am interested to see what happens with this.

By the way, just for reference, our final drive ratio is 4.45:1.

Don't believe me? Look up this BMW TSB: 00 01 95 (2147)
Thw title will be: 318TI GENERAL INFORMATION - TECHNICAL SERVICE BULLETIN
It will be dated September, 1995.

[motoracer47]

Originally Posted by Dusty_Hale

Exactly my point. The Speedo is run off of the diff. If you change the ratio so that it spins faster, you would need a speedo gear that is calibrated to that ratio, right?

I understand your logic, but in this case...no. The speedo pickup is on the passenger side output shaft, same as mz3 diffs. The output shafts will always rotate at the same rpm for a given speed regardless of the diff ratio infront of it. The only thing that would make you re-program would be going to a different diameter tire. In other words: If you go 60mph, the passenger side output shaft will spin at the same rpm regardless if the diff is 4.10 or 4.40.The only difference will be the engines rpm to achieve said speed.