How Do I Know If My Trans Is Original?
 

I need to replace my trans and I learned that there are 3 different auto tranny's for my car. (91 300 SL). My #'s are 500-493751. Anyway I ask why I cant use any one and they told me the wiring is different as waell as the ratio etc. Ive since noticed some spliced wires on my trans and now Im concerned that it might not be the right one all together. And Is it possile for the torque converter to be locked up??? Thank you all for reading any help is awsome.

The number you have given bears no resemblance to a transmission number.

What is your transmission number? It should start 722.500
With your full chassis number the original full transmission number can be had.

For instance I looked up a customers chassis number for a 91 300sl WDBFA61E2MF030542 and got trans number 722.500 03 503646.

After looking at this I suppose your full number must be 722.500 03 493751. Give me your chassis number and I'll see what the car came with.