Does anyone know if the 2wd 4 speed auto for the 4.3l v6 will bolt up to a 350? As far as I have heard the 4.3 is a 350 minus the front 2 cylinders. But that would be too easy. I have a 2002 2wd 4dr. I have not kept up on the newer engines. For me it is mouse and rat engines. I am old but still kicking. Thank for any info you can provide, Tom.

 

Yes. The 4.3 and sbc share the same bolt pattern

 

It will work but you need to have the right flex plate and torque converter. This will depend on if you have a 350 with 2 piece rear main seal, or a 1 piece rear main seal.

IIRC the 1 piece rear main seal 350s (I believe 2000 was the last year) will hook up directly to the 4L60E transmissions using the original 350 flex plate, since the 4.3's are also 1-piece rear main seal engines. Not sure if you can use the 4.3 flex plate on the 350 - some goofy balancing on the 1-piece rear main 350 engines vs even-fire V6's. So make sure you get the flex plate with the donor engine.

On the earlier 2-piece rear main seal engines, I believe they require some sort of spacer or different torque converter to bolt the torque converter up to the 4L60E correctly. You would have to investigate that further if you have a 2-piece rear main 350 to install.

You will want to speak with someone knowledgeable to re-program the transmission shifting so it will last behind the increased torque of the V8. They are not the most rugged trans, but my 2004 4x4 Avalanche does have a 4L60E as well. It's a 6000# vehicle and I tow 5000# with it some (gently). It has a towing button on the shift lever that REALLY firms up the shifts, so I know it can be done electronically. Not sure if there are any major differences in the transmissions themselves. I think you could Google that.