harry697

iTrader: (118)

I would put my money on the rpm cases being the root of your problem. They're either defective or have warped/worn from that motor you're running. My guess would be defective cases that aren't symmetrical, causing the gears to fail on an angle. As mentioned, the RPM gear box material is much softer than any other trans cases I've seen. Could just be flexing too much from all that torque.

One other thing I noticed in your pics. The diff bearings aren't in the case halves. Did you remove them for some reason or did they pull out when you removed the diff? If those bearings don't have a light press fit into the cases, you can get excessive play and strip the gears. Had the same thing happen on my etruggy. The inner pinion bearing recess got egged out over time, causing the pinion to deflect away from the ring gear under hard acceleration and braking. Wiped out a new set of gears before I found the worn gearbox.

smirkracing

Thanks to everyone for the great advice and tips.

I re-built the gearbox, and on the firs run, the main diff gear stripped and broke some teeth. When I went over all the gears, I discovered the top gear (which had not broken) had some very small piece of metal in the teeth that caused the idler gear to jump 1 time every revolution, and I think that is what caused the diff gear to break.

I did some quick tests and it seemed to be working so far.

Hard to believe something so tiny (literally 1mm by 1mm piece of metal) wedged in the teeth could cause so much damage.

SocalSnakeEyes

iTrader: (6)

Happens to the best of us. Guess I shouldn't have ran that plastic top gear with the alum idler. Good thing it was only 27t motor.
upgrade time.

ta_man

iTrader: (153)

Puzzling that you are having this problem. I run the plastic top gear and the aluminum idler with a castle 4-pole 4600KV motor. Been doing it for about 2 years now. AFAIK, the aluminum idler should only be run with plastic top and diff gears.

ljl23

iTrader: (4)

I would agree with the others. Replace the transmission case: there might have been a slight tweak that caused the gear mesh inside to be messed up on the RPM transmission case. I, haven't had good luck with the RPM case either. The suspension arm mounts were so tight on the pin I had to drill out the hole so the arm won't bind.

SocalSnakeEyes

iTrader: (6)

One of the first times I've had it happen. He was using reverse to forward a lot. That may have had something to do with it. Or the slipper was to tight as well as it being the old peg type. All that a side now it updated to the all metal gears. Next a top shaft for the AE type slipper.

FYI the new black pegs are way to long and let the spur wonder free side to side. It took two o rings just to get it Traxxas straight. I take them out as they wear down but, wow.