motor swap

Asked by Jun 23, 2016 at 10:08 PM about the 1998 GMC Sierra 1500 K1500 SLE 4WD Extended Cab SB

Question type: Car Customization

I'm looking at replacing the vortec 350 in my truck with a 6.5 turbo diesel. I don't need hate on my motor of choice, It's perfect for what I'm doing. My question is do I need my computer replaced (or flashed) for it to run with my current setup or can I just swap the wiring harness?

7 Answers


Replacing a 350 gasoline engine with a diesel will require major modifications. Electronics, transmission, fuel system, exhaust and possibly suspension will all have to be modified or replaced. I would just look for another vehicle.


Find a GMC with the 6.5 turbo diesel buy it as a parts vehicle then change over the engine and all systems to your '98, This is the easiest method.


2 good answers....but why is my question....

I have been building this truck from the ground up, I got the diesel out of a 94 silverado and had it rebuild and upgraded to work with the 98. Basically everything's been done but the electronics up on the motor. I have the new harness, only thing I don't have is the computer. I have the computer from the original 350, which leads me back to my question, can that be flashed or does it have to be replaced with one from a truck with a diesel?

The reason why kelly is that this project is something I started with a close family member who has since passed away. This has a huge amount of sentimental value to me so the extra cost and work are well worth it to me.


This requires the computer (Diesel) from the '94 Silverado.

I've upgraded the 6.5 to the late 90s specs. Updated heads, sensors, fuel system, and accessories. It's no longer compatible with the older computer. I know I can buy a computer for a 98 6.5 with my setup but it would have to be flashed by the dealership. I'm just wondering if I can have the computer I have for the 350 reprogrammed (flashed) to run the 6.5

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