It’s been awhile since I sold my Think. Get underneath it and start checking any kind of joints that may be loose. I do remember replacing all my ball joints as they were worn down bad. Can’t remember if these had u-joints but I would def check out the driving shafts coming from the motor.
There are two CV joints going to each rear axle. You should also encounter the same “clunk” going from reverse to forward.
There are other possibilities as well, like an axle bearing or something inside the transfer case.
If you jack up the rear and support the vehicle on jack-stands, you should be able to duplicate the problem by HAND with a helper… and locate the exact source of the noise. You could also actually energize it as well, but I would not advise you to be under the cart… although it is something I might do.
Well, it has been a long saga, but the grind is finally fixed.
Differential fluid was gross and thick. Couldn’t be cleaned out even with chemicals, so replaced differential
U joints were sloppy – replaced u-joints and half shafts
still had grinding noise, but it was slightly better
finally figured it out. I had a black motor installed and (OK I may be describing this wrong) and the motor drive coupler was the wrong size, thus it was grinding apart the ?? Anyway, we installed a proper size and all is well.
Perhaps another question you can answer?? Can I put a trailer hitch on the Think? I want to haul a little yard wagon around.