Bhop73 made a post similar to this one. I think my experience may be a little different and that's the reason for the new posting.

Took out the 142 Tiger for a shakedown yesterday. Up and down the hills she went, through sand, rocks, shells, clay, mulch, etc. The little tiny shells disabled that Tiger's running gear in short order! I cleared the tracks several times but now she didn't like turning left anymore. At first you could hear the motor sounds from the speaker but no movement. Listening closer it sounded like the motor was going full tilt but the sprocket wasn't moving. Took everything apart and tested it out. Fine. Cut away some more of the speaker box and insulated the antenna wire. Put it all back together again. Same thing. Took the tracks off, worked fine. Back together same problem! Apart again, this time putting my thumb harder against the sprocket for more resistance, BINGO!!

The gear was split on the shaft leading to the sprocket. The Sprocket is cracked too! Dang, that nice weathering job and now a new sprocket! Ohh well, now the new sprocket will have fresh paint and lots of black grease from the dirty hands that put it on! What to do about the gear? Replace it with another plastic one? That was my thinking but this tank is for my buddy and he is a United States Marine. It wouldn't last 4 minutes come to think of it! Metal sprockets, Idlers, Gears and Tracks here we come! Better add some L brackets inside the hull to beef it up and seal it off from the elements too!

Ohh another Faux Pah on my part. I never realized that there were different shaft sizes on the gearboxes! Sorry for the misinformation guys!