AMP Buggy- One rear wheel not spinning

brownhousechris

New Member
Messages
4
HI all, new to this forum (and RC in general). My son has an ECX AMP dune buggy. Lately, he has had an issue where one rear wheel will spin when the throttle is pressed, but the other wheel spins slowly or not at all. When I turn one wheel backwards by hand (no throttle) the opposite wheel spins in the opposite direction, which I gather is what is supposed to happen. I don't know much about these, but I can take stuff apart and get replacement parts. Could it be the differential? Or some sort of seized bearing on the non-spinning wheel? Any advice greatly appreciated.
 

X

Conspiracy of One
Staff member
Supporting Member
Messages
1,038
Remove the wheel on the side that doesn't move with throttle. Take a look at the hex on the back side of the wheel as well as the hex hub on the axle. Are they stripped? Make sure the pin is inside the hex hub as well.
 

brownhousechris

New Member
Messages
4
Remove the wheel on the side that doesn't move with throttle. Take a look at the hex on the back side of the wheel as well as the hex hub on the axle. Are they stripped? Make sure the pin is inside the hex hub as well.
Thanks, I will try that tonight! However, when I was messing around with it last night I noticed that the axle, on the side with the non-spinning wheel, was also not really turning. This leads me to think it's an issue with the gearing or differential, but I don't know very much. I will let you know what I find.
 

X

Conspiracy of One
Staff member
Supporting Member
Messages
1,038
Thanks, I will try that tonight! However, when I was messing around with it last night I noticed that the axle, on the side with the non-spinning wheel, was also not really turning. This leads me to think it's an issue with the gearing or differential, but I don't know very much. I will let you know what I find.
That being the case, it could certainly be the diff or perhaps the bearing on the outdrive of the diff on that side. Another thing to look at is the set pin for the driveshaft, perhaps it fell out? Number 48 below.

1544130607775.png
 

brownhousechris

New Member
Messages
4
OK, I finally checked this out tonight. Both set pins were in just fine. What I found is that when I spin what would be the passenger-side wheel, the driver-side wheel spins in the opposite direction. BUT, when I spin just the driver-side wheel, the opposite wheel only spins a little, or not at all. This seems to be mostly when I spin the driver-side wheel in one direction (sorry, can't remember if it was forwards or backwards). When I spin it the other way it seems like something grabs, and then the opposite wheel turns. I feel like I can also hear something like a gear not catching when the opposite wheel does not spin. Does this make any sense? My instincts tell me to get a new gear set, but I'm open to ideas too. Thanks very much!
 

Jddemelfi

Member
Messages
12
If your vehicle moves forward and reverse properly and this only occurs when you have the vehicle in the air and you spin the wheels it's most likely normal differential action good sir. Before I hung up the wrenchhes. On a full size car if you put it on a rack and spin a rear wheel by hand the diff will sometimes make the otherside spin backwards.
. Other than that it's the spider gears in the diff moving at different rates. These diffs are really easy to rebuild in these cars.
 
Last edited:

Jddemelfi

Member
Messages
12
Thanks for the input. Unfortunately the vehicle is not moving OK, it barely moves forward or backward
Okay than you deffinately want to open up the case halfs and take a look at what gear went. I had similar symptoms when I first went brushless I shredded my idler gear
 

HeavyBag

Well-Known Member
Messages
49
Well, at least you, brownhousechris, will get the opportunity to get some wrenching time in. That's the great part of owning a hobby grade RC. Assuming it's the first time opening up the gearbox, will get to see what spares to keep on hand if no hobby shop inventory is around. Also, it's a great time to clean and relube them bearings, especially the bearings on both sides of the diff.
 

Joeblow513

New Member
Messages
1
I had the same issue with my amp! My problem was the stock driveshaft broke internally right where the plastic meets the metal. U couldn't see any on the outside whatsoever. I didn't realize this until I removed the wheel held the metal axle part by hand an gave it throttle only to see the driveshaft spinning but the axle. Google hot racing metal driveshaft for ecx amp and it will pop right up. I'm pretty sure they make 3 different types I went with the cheapest which were around 35 or 40 and they had the best reviews out of the bunch. And durable. Money well spent never had they problem again. Hope this helped don't forget to check ur bearings4689stock. Broke internally where my finger is4690
 
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