i'm for thinking it would be the heat sink cooler on the firewall. horizontal in and out tubes [?] causing air in the system when the engine was shut off, and the fluid was suddenly dumped back into the transmission. however, since the transmission was changed, and it stopped, [still using the horizontal firewall mounted cooler ?] that throws out my thoughts, so ?
i realize factory coolers in front of the radiator are as high [?] but they usually have bottom in/out tubes.