Reward for a correct answer on EFILive Very odd behavior with regards to Tire Size

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Facts:
GMT800 Hummer H2
Duramax LBZ / Allison 1000 6spd
37" Tires
H2 Final Drive 410
Duramax donor had 373

Issue:
I'm trying to do a tire size adjustment in order to correct my speedo. Initially speedo was of 9mph at 70 cruise. It was reading faster than GPS speed. I use the Speedo Calculator and determined that 36.8" tires height was 548.05 rev/mile. (Tire manufacture says 565) After adjusting I was within 6mph off. Tried and tried and nothing helped. out of desperation, I began a series of flashes with different values I ended up with 604 rev/mile which according to the calculator is a 33.3" Tire.

Why this odd behavior and what else is being thrown off by correcting my speedo.

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Looking deeper I opened the stock TCM for the very first time and see a speedo parameter there as well. Do I change things here as well ECM?
Revs/mile are 682
Final Drive ration is 410
axle ratio shows 373
I got to believe this has something to do with the issue but I don't know what to do.

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Changed TCM to match ECM but also adjusted to 410 on the ECM at the same time. This did the trick but don't know whether it is attributed to the ECM or TCM change. Finally, all good now!