stroker

what makes them few extra horsepower in the ho for them years......thanks ........

redram

As far as I know it's changes in the computer software of the ECM.<br>The '03 HO's have some more durable engine parts than '03 standard output,apparently. Not sure if this is the case with previous HO's.

TPilaske

So was it just the weaker auto tranny that couldn't handle the output on the previous HO's? Is that why it wasn't available until the 48RE came out?

redram

Did some checking and there are a few other things different from ETH(HO) to the ETC(standard output):<br>-ETH uses larger turbo, HX35W<br>-ETH has higher output injector pump<br>-ETH has higher compression<br><br>TPilaske-I believe the main reason was that neither the 47RE nor the NV4500 could handle the HO torque.

Scotty

And the ECM's are very different...I tried to swap out an ETC and ETH ECM and I got SFA...in other words nuttin from the ETC and the ETH sounded like it was banging a piston against the head. :

Pit Bull

different injectors, different pistons, valve inserts, VP44 is different, ECM is different, Larger shaft for the 6 speed transmission.