Diff with step and manual cars

[C.junior]

Is the only difference the transmission or Is the differential and anything else different?

[Pig Farmer]

Manual has a taller final ratio in the differential and the ring gear is welded. The auto's ring gear is bolted making the LSD swap a bit easier/cheaper. Many manual car's have converted to the auto's differential/ring gear when building a LSD which gives you quicker acceleration at the cost of a slightly reduced top speed.

[mike the snake]

Isn't the manual diff bigger and stronger too? I remember seeing pics someone posted, and the auto diff spider gears looked like sintered cast metal and smaller, whereas the manual innards looked forged and bigger.

[GeeRam]

Originally Posted by mike the snake

Isn't the manual diff bigger and stronger too? I remember seeing pics someone posted, and the auto diff spider gears looked like sintered cast metal and smaller, whereas the manual innards looked forged and bigger.

Correct.

The Steptronic 135 has the small casing rear diff assembly (as per the 130i) whereas the 6MT and DCT cars have the larger casing version.

Here is the thread you were probably thinking of.

http://www.1addicts.com/forums/showthread.php?t=657738