engine conversation

[Eugene]

I have a2004.5 lly 2500HD going to change engine to a 2006 lbz What tune is needed and what mods have to be done.I am going to keep the 5speed trans.

[THEFERMANATOR]

If you are keeping the 5 speed trans, then I assume you are going to keep the LLY ECM to run it? It would sort of defeat the purpose of going to an LBZ and staying with the 5 speed IMHO. The main reason to do a swap is to either go from an LB7 to get teh inejctors outside the valve covers, or to go to an LBZ for the 6 speed. If you do make the swap, you will have to stick with the LLY ECM as the BOSCH ECM will not communicate with the 5 speed TCM directly. If you do, you will have to go into the engine and change out the timing reluctor wheels as the LBZ has 1 more tooth than the 01-05 did. If you want to go with the LBZ BOSCH ECM, then you will have to go with a 6 speed trans and TCM to make it all work like stock.