Gear at Speed Question: 7AT

Jordo!

Something I've found to be a little irritating about the 7AT, which I am otherwise extremely pleased with.

I notice that 4th gear appears to be very particular regarding road speed and RPM -- that is, on coast down, the ECU is especially picky about being in 4th vs. 3rd.

Put another way, I invariably down shift at the correct engine/road speed, and thus am not beaten to the down shift on coast down by the 7AT.

The one exception is 4th gear. 2nd, 3rd, 5th and higher all seem to allow one to coast down to very low speeds without initiating an automatic down shift to prevent stalling.

It's not a big deal, but occasionally I will miss the downshift at low speeds, and if I fail to drop a cog at about 1900 RPM, the ECU may beat me to it, and suddenly I am in 2nd, revving higher than is needed.

Is there a specific mechanical reason why 4th is very picky? Are 3rd and 4th just especially close.

Anyone have any thoughts on this, strictly from a mechanical standpoint?

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