2007 4.8 to 2008 4.8

[Robert18]

bought a 2007 silverado 2wd 4.8 with 15,000 miles to install in my 2008 silverado 4wd which came with 4.8. Changed oil pan and motor mounts. Crankshaft sensor on 2008 is on front and 2007 is on back. Re-routed wire to back. Truck will not start. Will it need to be re-programed

[Blasphemy]

Do both engines have AFM/VVT? Check and double check all your connections, specifically your grounds.

[farmtruc]

The 07/08 are wired the same. So that is fine. ECM wise.
All the gen3 and gen 4 engines have the crank sensor behind the starter, towards the back.

All gen4 engines have the cam sensor in the front. On the timing cover.


We need more info.

[farmtruc]

Another fyi. 4.8 didn't have vvt or afm in 07/08
So it sounds like u forgot about the Crank sensor wire that is on the truck harness and accidentally rerouted the cam sensor to the back. Maybe?
Truck won't start without a crank signal. That's where it all starts.
Find the crank sensor connector on the trucks harness and plug it in behind the starter.
Find the cam sensor connector on the trucks harness and plug it in the timing cover.

Both those engines should be the same so wiring won't change.
If one of those engines have afm it's a 5.3

[Lextech]

Wouldn't the 2007 have a 24x crank reluctor and the 2008 have a 58x crank reluctor?

Jeff

[Frenchy]

I'm thinking it's a 07 Classic, so Gen3. Maybe

[farmtruc]

regardless of engine generation, crank sensor will always be in the back, behind starter.
He mentioned re-routed, so that might be the cam sensor he re-routed.

look at the crank sensor, black is gen3, grey is gen4

we just need more info

[Blasphemy]

I thought the same thing Jeff. When GM was transitioning to the gen 4 platform, it was a sloppy transition because there were a lot of motors with and without AFM/VVT designs. I read a quote in an LS book that I have from a GM engineer who said that the move from gen 3 to gen 4 wasn't a cut and dry move, it was spread out over a few years and models. I'll find that quote and post it later. On a more relevant note though, if the OP wants a more educated guess, we're all going to need more info about each motor and maybe pics also.

Wouldn't the 2007 have a 24x crank reluctor and the 2008 have a 58x crank reluctor?

Jeff

[Robert18]

The original motor has the cam sensor on the timing cover... The 07 has a cam sensor in the back around the oil pressure sensor. Is there any way around that?

[farmtruc]

Look at my post above regarding crank sensors. Sounds like a reluctor wheel issue.
Meaning gen3 vs gen4

If the engine is newer than the truck. Meaning is the engine a gen4. Then u need a lingenfelter box