LSD vs open differential and my 94 325i

B

bmwperson

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#1
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Chicago,IL
#1
Hey, I recently crashed my 325i 94 automatic... now since I have a 92 325i and I heard that automatics have higher ratios for smother ride maybe I would be able to switch em? Bunch of questions:
1. Whats the ratio in my 92 325i manual?
2. Whats the ratio in my 94 325i automatic?
3. If i change em how much will the preformance increase?
4. Whats the difference between a LSD ( Limited Slip differential ) and a open one?

--
Thanks
Tom
 
wood_e

wood_e

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Ames, IA / St. Paul, MN
#2
I can field # 4

On an open diff only one tire gets power to the ground in high power situations. With an LSD both tires get power, and improved grip (since both tires are putting power to the road). LSDs are worth the money...
 
K

kev415

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Northwood, NH
#4
If you steepen up the final drive ration by increasing the rear differential from 3.28:1 (I think) to 3.55 or even to 3.73 area ( i dont know exactly waht is available for the bimmer rear ends), you will experience a huge difference. The car will seem lighter, you will accelerate faster and the throttle will become more agile, especially since you are missing out on the VVT in the '92. You will however loose a little off of your top speed, but how often do you drive at 120 mph? If you live in a hilly region you may see a increase in gas milage as it reduces stress on the engine when you gear up. You are also reducing strain on the transmission, and I bet you will even find your 5-spd to respond a lot better to the new gears.

In the mark VIII I switched from the stock 3.08 gears to a new Cobra pumpkin with LSDs and I swap between 4.10s (track) and 3.73s (street). With over 300 hp going ot it, the 4.10s really make the car dance. Feels like a little sports car compared the what the 2-ton beast felt like with stock gears.
 
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