Is a tune always necessary? Gen 3 Coyote swap

[Scott88]

Im putting a 2018 gen 3 coyote in a 2005 chassis. I've used nearly everything from the donor vic: to include tranny, exhaust manifolds with cats, CAI, PCU, etc. However, the gear ratio in the pumpkin is 4.10 and the 2018s have something lower (I think 3.55). It's a manual transmission; do I need to retune the engine for just one change? (Not going for max HP, but for max reliability). If so, what are the negative impacts? Just the speedometer reading a little faster than the real speed?

 

[Iceman62]

If you're taking the time/effort & $pending all the $$$ to complete this major overhaul = why not add some $$$ for tune (IMO)? Could be good starting point for ensuring upgrade's successful & set for future mods...

 

[Scott88]

Thanks for the advice on spending $, but still doing the research to learn more about this hobby/passion.