Wraith question

[surgetek]

Hey all,

So I am putting together a Wraith for my son with all the parts I have swapped out of mine.

I picked up full assembled axles and slapped them on not thinking about taking them apart to make sure they were all set. They were new from an RTR.

So I have it together and I started driving it around my garage and attempt to crawl up a small step. Once it hits resistance the motor and pinion spin but the spur won't. My first idea was slipper. So I loosened it a little and tested it, same thing. I took the slipper apart and no issues. When I had the tranny in my original Wraith, it was fine.

So my thought it possibly the diffs? I'm going to open them tonight regardless.

Any ideas?

[novarider]

If the pinion spins and the spur doesn't does the spur have stripped gears?

[surgetek]

No it's perfect, well after all this I may have to get another to be safe.

I think a diff is binding.

[sdmf]

Idler gear?

[Poprivet]

Slipper?

[Eric0424]

Is there any noise associated with the slipping??

The only way a pinion can spin without moving the spur is if the spur is stripped or the gear mesh is too loose. Check your spur for damage, check your gear mesh, make sure the pinion set screw and motor screws are tight and check the pins in the top shaft to see if one or both are broken or missing. Also you tighten your slipper instead of loosening it if/when you have too much slip in the drivetrain, if the slipper is/was the culprit it was too loose.

If the spur is moving with the pinion and the driveshafts are not spinning, then something in the transmission is stripped or loose or the screw pins for the driveshaft at the transmission could be missing/damaged. If the spur, pinion and driveshafts are spinning, then there may be a problem in the axles or the driveshaft screw pins at the axle may be missing/damaged.

[surgetek]

Yeah when I do the slipper test (put my radio on one wheel and hold the other) it has the grinding sound. I also had it on a stand grabbed one wheel and same thing.

Slipper is tightened. I took it part last night to make sure I didn't miss something. The mesh I thought was fine, held the pinion and rocked the spur a fraction. May not be able to get any paper in the I am not sure, I usually go by feel. The whole thing is brand new. When I built it, I just test drove it in in my garage the same I did with this with no issues. The only thing that changed was the axles so that's why I thought of those.

It only happens when under a load. Everything is perfect while driving of flat ground.

[Eric0424]

A grinding noise usually means a stripped gear or gears slipping past each other, but loose set screws and/or broken screw pins and drive pins (like the topshaft gear pin) can sound the same. If you're tearing it down just triple check everything.

[surgetek]

I swapped out the motor and the pinion last night and same thing.

I actually looked right at the pinion and spur and watched the pinion move and spur stay. I'll grab another just for shiggles.

[sdmf]

Have you opened your transmission?

[surgetek]

That's next, I am trying to work my way into that. I didn't start there because I drove it around for 3-4 minutes with no issue before I attempted anything else. I went right to the slipper.

[Eric0424]

Are you sure the pinion is actually spinning and not just vibrating?? I've seen that happen twice. First time was a loose pinion set screw. Under load the motor shaft would spin inside the pinion gear vibrating the pinion, it appeared to be spinning but wasn't. The pinion was snug on the shaft so it appeared to be tight. The second time was a motor or sensor cable issue, also vibrating the pinion gear making it look like it was spinning.

It's physically impossible for the pinion to spin without spinning the spur gear unless there's a mesh problem or stripped/broken teeth on one or both gears. Your mesh sounds fine and you would notice stripped or broken teeth. That's why I'm thinking the motor/pinion may just be vibrating back & forth instead of spinning.

[surgetek]

I'll check. It's a different motor (both Tekin 35t and HH 45t) and different pinions in all combinations. I'd have to get the screw tight at least once. I'll look closer tonight.

[Eric0424]

Originally Posted by surgetek

I'll check. It's a different motor (both Tekin 35t and HH 45t) and different pinions in all combinations. I'd have to get the screw tight at least once. I'll look closer tonight.

That's what makes this odd, you would have noticed and tightened a loose pinion and two bad motors is unlikely (although not impossible). After the motor swap I would swap in a new sensor cable, if for no other reason than to eliminate it from the pool of suspects.

There is the possibility it's electrical. As in the battery and/or motor power wire connections. I've had cold or weak solder joints and a couple of bad connectors run fine under light load then shut down or brown out under a heavy load. If the ESC is not shutting down or browning out and then resetting itself, then there may be a problem the motor wires.

[surgetek]

Both are brushed motors and the ESC is a Sidewinder, all brand new. Sidewinder is programmed for brushed.

I'll get there.

[surgetek]

So I went back into my stock parts and grabbed the 20 tooth pinion that came in the kit and tried it. Low and behold, it works perfect. Not sure what is up and I am not going to try and figure it out. The pinions I was using are the same pitch, at least I thought the were.

Thanks for all the help and suggestions.