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Discussion Starter #1
Hello all...

My L03 305 V8 has recently died due to a worn out timing chain and i have located a donor truck with a 5.7 in it...However the donor is a K2500 4x4 while my Sierra is a C1500 2wd. What all is needed from the donor truck to transplant this 5.7? The Sierra has a TH400 trans which i would like to reuse behind the new engine i know the engine will phyiscally swap bolt for bolt but do i just use the ECM from the donor in place of my stock ECM? The one area i see possable issue is where the trans is concerned...it sounds like the donor is the same year as my sierra but the guy im buying the parts from isnt certian hence my questions...What all is needed from the donor truck?
 

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The engine will bolt in, you can use your existing ECM and either the new intake and exhaust manifolds or your old ones, The new trans is a short tail shaft model (4x4) so you'll have to locate a long tail shaft (2x4) to bolt on the trans. Isnt your existing trans is a 700R4? The TH400 is a 3 speed trans so you'll lose a gear.
 

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The truck was a fleet truck and it was ordered with the TH400. Im assuming the existing trans will work except i may have to change the flex plate on the engine. Nice to know i just need to change the chip in the ECM didnt realise both engines used the same one...just different chips for their displacement..
 

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just something else im wondering when it comes to this 5.7 swap...im going to be going through the engine first before i install it. What sort of upgrades should i add to bump up the engines performance? This truck will be driven on the street only and it currently has the TH400 and 3:08 gears in the rear diff. Chances are i will be running stock size tires up front (235/75R15) and 29" pro street style tires in the rear. the rear tires im looking at running are 29 x 12.50 R15s will those fit within the stock wheel wells on the rear of the truck?
 
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