crakhead

Hi everybody !!


I have a 1999 silverado 2x4 with the 4.3 and I'm looking to swap a 5.3 vortec into it. The engine is a 2001 I think so is the same generation of my truck. I want to know if it's possible and how hard this swap is !! I know I have the skills to do the job but I'm not very familiar with this brand. By the way my truck have a automatic transmission as been recently rebuild and I want to know if the 5.3 engine will fit my 4.3 auto tranny ... I know sbc will fit but I don't know if the 5.3 have the same bolt pattern for the tranny !! and for the wiring, suppose I have the original harness from the 5.3 is it a big deal to fit this on my truck ? is it compatible ?? 'cause my 4.3 run with a distributor and the 5.3 have coil pack ... if someone here can help me with that I'll appreciate thanks !!

Bluewhale

Your trans will bolt up to it. Hopefully you have the complete engine compartment wiring harness from the firewall forward. That will make things a lot easier.

crakhead

and for the engine wiring harness if I had the complete 5.3 harness from the same generation of truck can i just plug and play or i'm gonna have some modification to do ??

Bluewhale

I cant be for certain in that generation truck, (not my wheelhouse) but i think it would plug in. I cant see GM making a different body/dash harness for a different engine, but stranger things have happened with transition years and such.
Your best bet would be to go to the dealer and get a part number for you trucks body harness, and see if it crosses to a V8.

crakhead

I've done the swap and it's work !! the wiring was plug directly at the same place and everythings is working !! I need to set the passlock for the new ecu and it's work but I have 3 troubles ...


#1 : when the engine is cold it start pretty normaly but when I let it run and turn it off, few minute later the engine start but it take time to fire up ... my dad think it could be the injector who's leaking with the engine off ....


#2 : when I start the engine (cold) the idle is low ... just like the choke (fast idle) did'nt work but I have a preston hose came out the throttle body to the rad and he's not connect for the moment, I put a plug on it I don't know if this work with the fast idle when the engine is cold ...


#3 : I go on the freeway with the truck, everythings work fine, the trans shift all the gear but .... when I hit the gaz pedal, no kick down !! the trans stay on the 4th gear !!


If someone can help me with this i'll apreciate !! thanks

crakhead

damn I juste saw that I've forgot to plug the tps ...... beginner mistake lol !! this will probably help on starting and maybe for the trans downshift probleme !! I'll try it tonight after work ... but I unplug the vaccum line on the fuel pressure regulator and I have little bit of fuel on the vaccum line,, probably a bad regulator ..