I did paused a scratch-mod development severals months ago and now i've found that the clutch is overheating due to a constant +4000 "Q to clutch" value. I can't remember if it was behaving like that months ago or is something that appeared from an update, but that doesn't matter because i've tested with official engine+gearbox+differential+wheel values and i keep getting 'Q to clutch' between 4000-7000 most of the time when engaged and throttling, even with arcade gearbox. I'm a little lost with that and though maybe physics system (beams/nodes and even weights) are involved on how clutch forces works?
If you haven't already, a good first step could be to take a look at the drivetrain debug app. Just to make sure that everything is connected up properly.
Thinking out loud here, but watch the speedometer inside the car, does it jitter? The wheels might be speeding up and down very quickly due to instabilities in the vehicle jbeam. These forces are then transmitted back through the transmission and drivetrain, and if they are large enough to overcome the clutch strength, then you have an issue. Perhaps your nodeweights are too low around the wheels? I'm not a jbeam expert however.
Really thank you!! wheels were causing entire differential rotation forces so they were pulling the driveshaft, making a lot of force on there