1997 4.3 to 1998 5.7 swap

[BadBowtie]

Hi everyone,
I am in the middle of swapping the 1998 5.7 into the 1997 4.3 CK truck. The 1998 5.7 is a suburban, have both complete trucks , I know i will be switching harnesses in the engine bay and motor mounts have to be swapped . But with all that's going on I was wondering if anything in the trans needs to be changed ? Going from 4.3 to 5.7 is there gonna be a change in the converters ? Any harness replies would be appreciated. Thanks in advance.

 

[df2x4]

You should be fine. The 4.3L converters have a slightly higher stall speed than the V8 converters so you may notice a little bit of difference in the way it takes off but it won't be anything serious.

EDIT - The PCMs changed between '97 and '98 though. I would do some research and make sure you're not creating any issues by swapping harnesses.

 

[BadBowtie]

Thanks

 

[Erik the Awful]

More torque raises your stall speed. You may have to change the converter, but as you're starting with a stock converter, it'll probably still be streetable. When I bought a converter for my Caddy's TH400, the transmission shop picked it, so my experience is limited.

If nothing else, call Hughes or another torque converter builder and ask. I'm sure they'll try and talk you into buying one of theirs, but ask for an honest opinion.

 

[L31MaxExpress]

4.3 converter is the same as the 96+ S10. Will give a drastic performance increase compared to the stock V8 converter. Under normal driving it will drive like it has the V6 in it still. Under heavy throttle it will stall higher and get the engine up into its powerband much more quickly.

I used a S10 converter in the 4L65E I had in my Express van. When I swapped to a 4L85E, I used a 4.3 V6 van converter for a 4L80E 2500 8-lug van.