A 6.5T going through a transmission with bushings instead of bearings without grease on the gears?
I'm surprised you got two runs out of it!
You need to replace the idler gear and diff gear and get yourself a full set of bearings for the car, or it will just self-destroy every single time. When you rebuild the gears get some grease onto the gears. Vampire Racing does some good stuff. Tamiya Ceramic Grease works well too.
Any car would have munched its gearbox with bushing and a 6.5T. Just hope you haven't been running it like that too long or you will have to replace the outdrives and top shaft as well.
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