What you say was true for the past, so the downvote was not necessary. But in 2019 they aim for even tighter cooperation.
https://finance.yahoo.com/news/red-bull ... ccounter=1
Speaking to Autosport, he said: "It was stupid, why should we make our own gearbox when we can get it from Red Bull?
"We have a synergy project, we have the rear end, we have parts from the front suspension, that's it.
"It's just totally simple, we have the Honda engine, we put on the Red Bull Technology gearbox, nothing more to say."
Committing to the same suspension will also mean that the two teams are likely to converge on an aerodynamic approach.
"We will have a very close cooperation with Red Bull Technology next year," said Tost.
"Because we will have the same rear part, which means the power unit, gearbox and the suspension - everything within the regulations - because we want to use this much.
"The front suspension as well, the inner parts, not the outer parts, that's all.
"But that's a lot, because you know the complete rear part means also the hydraulics, the electronics, all this kind of stuff."
Toyoharu Tanabe seems to think that TR will also use RBR gearbox externals in 2019:
https://www.pitpass.com/63753/Shared-Re ... efit-Honda
Usually, though it uses the same gearbox internals as Red Bull, Toro Rosso has opted to provide its own casing. This year however, both will run the same rear end including suspension, a move which Honda believes will greatly aid the Japanese manufacturer.
I think they will use as much 2019 parts as allowed to decrease costs and also make it easier for Honda to push on the engine side. I would'n t be too surprised if the STR14 will look like RB14 in terms of aerodynamics.