To be clear on a couple of things The back of the Prius engine generation 3 is connected exactly to what The flywheel the torque plate the shaft that slides into that is? MG1 MG2? I'm trying to isolate a noise that I know is coming from the transmission that is right around the time when the engine is being called up by the car nothing stutters the engine runs perfectly there is no miss If I step through it the car takes off right up to 80 mph without any problems runs great. But going slow say 3540 when I'm driving down the road and my pedal pressure matches the speed that I'm going and the transmission electric motors and ice are trying to kind of bounce back and forth it looks like on the display The red lines coming from the motor stop going to the front wheels for a couple seconds I touch the gas very gently to keep the car going and the ice engine comes on I can see the red lines on the display I know it's running and then it growls at me is what it sounds like exactly literally and if I step on the gas a little more it steps right through the problem the engine just revs up the car takes off and that noise stops. But it sounds like it's from the input shaft from the transmission further into the transmission that's the only way I know how to explain it.
The engine crankshaft turns the flywheel, which has the torque damper mounted on it, which turns the input shaft. The input shaft turns the planet carrier of the power-split device. The PSD's sun gear is connected to MG1, and the PSD's ring gear is connected to the final drive and wheels, and also to the reduction gear from MG2. Sometimes you can guess which parts a sound is coming from if the sound is repetitive and reveals the RPM of the thing making it. If you know the engine RPM, you know the planet carrier RPM, it's the same. If you know the road speed, you know the ring gear RPM (mathing with the tire revs-per-mile and the final drive ratio), and you know the MG2 RPM (take the ring gear RPM and increase it by the reduction gear ratio). If you know the planet carrier RPM and the ring gear RPM, then you know the MG1 RPM (find it on the nomograph, using the other two). Really, the nomograph lets you start with the RPM of any two of those things and find the one you don't have. Also, if you have a scan tool, you can just read off the engine, MG1, and MG2 RPM. There could be other weirder possibilities. For example, some kind of defect between the planet gears and ring gear could make a sound reflecting the difference in RPM between those two parts—a sound that gets slower when those two bits get closer to matching each other's RPM. And then there are sounds ball or roller bearings can make. Pretty hard to characterize unless you know a lot about the bearing (how many balls, etc.) or you're holding it disassembled in your hand. I went through that once with a wheel bearing just to see if I could, but it wasn't anything I'd be able to do in my head.
I would say something is trying to slow down something I'll have to get tech out and look at RPMs if I can see the RPMs exactly when this is happening I'll have to have her drive while I watch the screen I guess but there are no codes no funny business The cars running pretty much excellent except when this happens and I'm afraid the transmission sounds like something's coming apart inside of it or something is very loose this is the low mileage takeout from the JDM people My original which was making no noise when the engine girdle failed and the piston rolled over in the rod broke that transmission was working fine I just thought I'd get a lower mileage takeout unit to go with the engine apparently maybe it was worse off than my original. But it's been fine for what like 6 months now I initially thought the fellow who put the engine in might have not tightened up the flywheel bolts before he put the torque plate and then slid the mess up together.
