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Serious problem with truck......video included

Old 10-23-2015, 12:17 PM
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Unhappy Serious problem with truck......video included

I have a Team Associated Rival, which up to this point has done me very well. I ordered some new LiPo batteries to replace the NiMHs that it came with from the factory. As I was driving the truck on the factory power before the new junk came, I was driving my truck around the front yard, the truck drifted to a stop and when I hit the throttle all of a sudden it started making a horrific grinding noise, similar to what a stripped spur gear would sound like. The motor would just spin, as well as the center differential.

I took off the spur gear/pinion cover, inspecting the spur gear and pinion expecting it to be a chewed gear, but no dice. both gears were in perfect shape and meshing properly. I couldnt figure out what the problem was. Frustrated, I put the truck away for the day and decided to come back later to diagnose it. The next day, I turned the truck on to try and find the issue again and.......wth....it worked fine. No grinding, just normal behavior. I was confused, but figured it was probably some debris that had gotten into the gears then worked its way free later. Cool, problem solved, or so I thought.


Fast forward a couple days, I got my new LiPo batteries in the mail. I went to run the truck for the first time using them (2 2s 5000mah 40-50c packs) and for the first 5 minutes or so the truck was doing great; ran much faster, was pulling wheelies, etc. Then, all of a sudden as I was running it around the front yard, same $#&% all over again. It would still move forward this time, but obviously not how it should, and it was still making this god awful noise. I ripped the slipper, center diff and all apart, hoping to find the culprit.....nothing. Hoping somehow magically I had fixed the issue by making sure everything was adjusted right, I put it back together and hoped the issue would be resolved........NOPE. The slipper is fully tightened, the mesh is set correctly, and there aren't any sheared gears or missing teeth!

I'm seriously scratching my head on this one, as I really can't for the best of me figure out what is wrong with this damn thing. I linked a video of what im dealing with below, can somebody give me some insight on this, and if it's a common problem or not?

https://www.rcuniverse.com/forum/*****************oOOt Any help MUCH appreciated
Old 10-24-2015, 08:26 PM
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Well I'm afraid the video doesn't help much, just tells me something got eaten in the drivetrain. You're going to have to do your own troubleshooting to narrow down your search of just blow the truck apart until you find the problem. Put the truck on a box or something with all 4 wheels off the ground or flip it over. Pick a wheel and spin it, does the other wheel on the same axle spin in the opposite direction? If not the take apart that diff. If it does spin in the opposite direction then try spinning both wheels on the same axle in the same direction. Does the center driveshaft spin, hear any funny noise coming from that diff? Is the other center driveshaft spinning in the opposite (since you have a center diff) direction? Do the same tests with the other axle. Also pop the wheels off and check to make sure the wheel hex isn't stripped out. Kind of doubt it's this as that sounds more like metal than plastic chewing on itself.

Last edited by Maj_Overdrive; 10-24-2015 at 08:28 PM.
Old 10-26-2015, 09:08 AM
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Yes, that is a horrific sounding problem. Since the obvious spur/pinion are "good to go", I would do a complete transmission inspection. Working from the center diff outwards, and inspecting the bearings for one that is "blown". Not only does the Rival have the typical 4wd/3 diff tranny, you got the extra two gears in the center gear box to inspect for possible mesh hick-ups.
Old 09-08-2016, 10:52 AM
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Thanks for the help guys, I "solved" the problem before by replacing the motor, and that seemed to work for the longest time, but now It's back. I'm hoping the motor isn't causing this again. The issue seems to be the exact same issue as before. Sorry to go graverobbing and bumping an old post, but I really don't get this. It honestly seems to be the center diff....BUT THERE IS NO VISIBLE PROBLEM. I'm not normally one to get this frustrated or even post asking for help but I'm seriously yanking my hair on this one.....
Old 09-08-2016, 11:45 AM
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The motor was the cause of all that ruckus before?

Was there a bearing blown in the motor? I've had that happen to me before, and I was not getting the best mesh possible between the pinion and spur. Still, kinda weird your problems went away for a while by replacing the motor <scratch head> .

I think I would be taking a look at the diffs. That just sounds like something is not meshing right. Something's jumping teeth somewhere.The way these RCs have "shimming" issues every other day, I'd check the shims under the spider gears. Heck, just check the gear's teeth for signs of "foul play". I know it is sometimes a disliked/lengthy job, but working your way in is a must situation this case IMO.
Old 09-08-2016, 02:16 PM
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Like Rusty said, the motor shouldn't be the cause unless the bearings went bad or the wrap on the rotor was disintegrating. It's unlikely both motors had the wrap on the rotor come apart, both having bad bearings would be believable if running in really diary conditions or if they were cleaned with a solvent that dried the bearings up.

I agree that sounds like gears though, metal on metal gears skipping. Follow Maj_Overdrive's post above concerning diagnosing. If you ca't figure out where to start after that resign yourself to having to take apart the whole thing. Start with the rear diff, they usually go first and you might get lucky. But while you're in there it would be a good time to shim the differentials to make them last as long as possible.

A note about the differentials themselves. You said you took them apart before and they looked fine. Teeth don't have to be broken off to cause this, they can be rounded off and just ground down. The spider gears can be particularly hard to see how worn they are without a new one next to it. Speaking of the spider gears make sure you pop out both sun gears and check them and the drive pins underneath them. The one inside the diff cup can be stubborn to remove but it's worth checking absolutely everything out.
Old 09-08-2016, 06:11 PM
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Originally Posted by RustyUs
The motor was the cause of all that ruckus before?

Was there a bearing blown in the motor? I've had that happen to me before, and I was not getting the best mesh possible between the pinion and spur. Still, kinda weird your problems went away for a while by replacing the motor <scratch head> .

I think I would be taking a look at the diffs. That just sounds like something is not meshing right. Something's jumping teeth somewhere.The way these RCs have "shimming" issues every other day, I'd check the shims under the spider gears. Heck, just check the gear's teeth for signs of "foul play". I know it is sometimes a disliked/lengthy job, but working your way in is a must situation this case IMO.
Thanks for the help AGAIN, rusty. That's exactly what I would describe it as is sometging jumping teeth. I have no problem doing a full teardown, I just was hoping for some advice where to start lol. I owe you one bud. Let mee do another inspection

The problem is i talked with the AE tech and showrd him the same video and even said himself he thoight it was probably the motor. So i replaced it in accordnace with the "expert" opinion. Lol.
Old 09-08-2016, 06:15 PM
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Im going to look into a shim kit if I can find one. Seems the most logical at this point. Thanks for the help
Old 09-09-2016, 05:04 AM
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Not that my 1/8 scale buggy is the same as the Rival's diffs, I just wanted to point out, after years go by, the manufacturer decides two are better than one. I can't remember how I built my diffs in the 8.2e, but the manual says to use one shim behind the spider/planet gears in each diff. The B3e uses the exact same 8.2e diffs, and the B3e manual now shows the use of two shims behind each spider/planet gear. After reading just about every post in a very long thread, I've prepared myself with extra shims just as a precaution. There were people needing shims after "breaking in" the gears, and some people had binding after adding the extra shim. Associated #81343 shims have the "blackish" shims included which I believe (not 100% sure) are the thinner shims of the bunch. I also will note that I can't be sure the shims will fit in a Rival diff. But I would bet they're are a good match.
Old 09-09-2016, 05:25 AM
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Just for poops and laughs...The shims for my 8.2e spider/planet gears measure 3.64 x 12.02 x .25mm thick. The material used in the "blackish" Associated v2 (posted above) shims are more than likely .14mm thick.
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