125c (3-speed) to 4T60 (4-speed) Conversion?

[Baddflash]

You'll need the console shift lever assembly itself. The 125-c shift assembly is completely different, and obviously only has the shift positions for the 125-c.

 

Why would the shift assembly be different between the 3 and 4 speed. I'm currently using the column and shifter from my 4-spd car on my 3-spd, so if the column shift is the same shouldn't the console shifter be too?? It's the connection at the trans that controls what position the shifter is allowed to move to, so if you put in the 4-spd the shifter should reach the extra gear just fine.

 

I took a quick look at the wiring today too. The gear selector wiring appears to be the same, the wiring for the TCC is different the 3-spd has 4 pins the 4-spd has 5 pins. I couldn't see the vss to check it but the 4t60 and 282 use the same connector so I don't see why the 3-spd would be different.

[KingArthur]

on my parts car (92 Lumina Euro) orignally had a 4 spd but someone swapped in a 3 spd. When talking about the shifter... when moving the lever from Park to the overdrive on the dash indicator is actually 'D' for the three speed. Now when i move the lever to 'D' on the dash indicator thats 2 gear for that tranny. What I'm saying is that the indicator is wrong for the three speed. It does't matter any way because i just need the motor out of that car, I'll sell the 3 speed anyway.