Big Rock My attempt to keep crud out of the 3s diff housing area.

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Velodromed

Snatching defeat from the jaws of victory!
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I’m in South Central, Texas, San Antonio area and we have extremely fine Colicchie dust. The particles are microns big and get into everything. I got into these 3S cars over two years ago and something I’ve noticed is that the diff housing will typically become contaminated with fine dust in a matter of two or three runs, turning it into paste. Then it compacts in between the teeth, helping lead to uneven tooth wear and differentials stripping.

I’ve tried different methods to slow the ingress of crap, from sealing it with extra grease to using a lot of grease inside to absorb the crud versus using very little grease to hopefully not absorb much crud… haven’t had much luck so I decided to try liquid gasket to try to seal the differential housing area better. I did six differentials between three cars around 5-6 weeks back and opened up two cars recently to check

The first car I opened up over a week ago results were mixed and I couldn’t tell much of a difference, so I figured it was probably worthless to try further. But i jumped the gun because on the two cars I took apart over the last several days, three the differentials were impressively clean. Junk still got inside, but it didn’t turn into gritty paste.

So I’m doing the process again to two cars and I’m being far more careful applying the liquid gasket. I am also using very little superlube grease as opposed to a lot, just smeared it into the gear teeth and no more. I will open up the cars in six-eight weeks and report back. Another cool thing about the three differentials that stayed relatively clean is they were a lot easier to clean up.

The first differential below is how they typically look when I open it up. The longer it’s been running the worse it is. The second picture is a differential that was sealed with gasket maker and run for six weeks in very dusty conditions. The third is another differential that had a sealed case.

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Compared to the "control" differential, the last two, especially the last one, are surprisingly unphased. You might be on to something!
I found that it was worth the time to do the gasket just because of how easy it was to clean lol. I think there will be a good result using just a very light amount of grease on the gears.
 
Nice write up. I've been using silicone grease around the edge of the diff case and the results have been better than not having grease. Like you said, the dirt mixes in with the grease and created a gasket. So if you've sealed every crack (and don't blast it with water or compressed air) it does okay at keeping everything else out.

So I'll continue atleast doing that.

Fwiw, I think alot of the discoloration in the grease over time comes from the gears slowly shaving themselves down and the particles of the gear teeth mixing in with the grease.
 
Nice write up. I've been using silicone grease around the edge of the diff case and the results have been better than not having grease. Like you said, the dirt mixes in with the grease and created a gasket. So if you've sealed every crack (and don't blast it with water or compressed air) it does okay at keeping everything else out.

So I'll continue atleast doing that.

Fwiw, I think alot of the discoloration in the grease over time comes from the gears slowly shaving themselves down and the particles of the gear teeth mixing in with the grease.
Thanks man! I agree with you on the plastic diff gears. Those will definitely shed dust. But the metal ones gunk up just as bad, so has to be the amount of grime getting in more then anything else. If I can just slow the infiltration down a good bit I’ll be happy.
 
Apparently arrma did something right at the factory for once. Opened up the rear diff on my son's granite, never been done before. It's almost spotless 👀
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After pulling apart several diffs that I’d used liquid gasket on I think it does help quite a bit. The one change I made is now I’m putting minimal grease just on the ring and input gear. I was using copious amounts before and think switching to minimal grease while using the gasket will give the best all around result. I’ve done this two cars and will run them for 2-3 months before checking. On another car I’m using minimal grease but no gasket so I have it to compare to the other cars.

One thing I noticed is on the diffs with gaskets the clean up was much less difficult because the grease didn’t turn into hardened paste and jamb down in between the gear teeth. That’s a very good thing and justifies the time spent applying the gasket.
 
Curious, are there any ARRMA RC models or other brands that use effective seals on all geared connections? New to the hobby, but coming from a background of doing mods on my Tacoma, including a full suspension swap, I am surprised by what appears to be the lack of attention in RC car engineering to keeping parts of vehicles that need to be clean and lubed, clean and lubed. While it is understood that using effective seals on differentials/gearboxes/CVs/etc. would raise the cost, you would think that on high end models, this would be implemented. Maybe it is, and it's my ignorance talking here.

I also have built bicycles as a hobby in the past, and am familiar with high quality sealed bearings that are essentially bulletproof and require no maintenance or lubrication for years of use. For example, the seal bearings in my crank bottom bracket and front wheel hub (both Phil Wood) are fully exposed to the elements, have seen plenty of water, dust and grime over the last 10 years, have not been touched or maintained in any way over that time, and are smoother now than when I first built the bike.

I suppose scale plays a large role hear as well, a reduced-scale zirk fitting might not be feasible to create, but you would think effective rubber gaskets wouldn't be too big of a deal to implement. Also, I don't understand why dust cover/shrouds are not standard. Yes, heat becomes an issue with a cover, but that can be effectively managed with fans and proper design of air flow through the internals (just like it is on real world vehicles, computer/server cases, etc.).
 
I was a cyclist 40 of my 52 years before I broke my neck and a bunch of other stuff. Can’t really compare equipment meant to carry people and often perform at a high level to what are basically toys. My mountain bikes, track bike and road bikes cost well over 20k plus the gear, maintaining etc. I have just a few grand invested in RC. If you want high end rc vehicles the cost is ridiculous and then you’ll have all the quality bearings, electrics and so forth.

Can sum it up basically like this. I can get a huffy for 200 bucks or less. A decent stump jumper for a couple grand. A high end bike such as Litespeed runs 8k or more. RC is the similar. Can spend as little or as much as you want. I like bashers. 3, 4 and 6s. I enjoy running them fairly hard and even more, I enjoy working on them. RC is fun, and a minor obsession for me. Cycling was a complete and utter life style that consumed much of my time and life for several decades.

Run a dust cover in 95-105 summer heat and you’ll kill your car. Even 80f heat can cause your car to hit high temps under a dust cover. I tried it on numerous cars for a year in south central Texas. I do not like my motors and esc to exceed 160° F and that’s impossible with a dust cover once it hits the mid 80s. But I do like to run one in winter when it’s really dry and dusty out.

I know a dust cover is appealing because it helps keep things clean, but it just doesn’t take the place of cleaning and maintaining the cars, which are a very important part of the hobby. I blow mine out with a blower and wipe down after every run. I tend to do full rebuilds every 3-4 months and partially rebuilds in between and regular maintenance on a constant basis. The better you maintain the cars the better they will perform as well as last longer. These things can take an extraordinary amount of abuse, much more than a bicycle or a 1:1 car. So can’t really compare them on equal terms. It’s OK to overthink things. Just don’t let overthinking get in the way of having fun.
 
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Yeah, people put WAY too much grease on their diffs, whenever I see someone smear red & tacky all over the place... o_O
 
Yeah, people put WAY too much grease on their diffs, whenever I see someone smear red & tacky all over the place... o_O
I figure there’s a reason aside from being cheap and poor quality control that Arrma only puts a dab of grease on the gears. That dab is often not even on the gears, but you know what I mean. I still had to try a bunch of different ways just to show myself.

The only thing I haven’t tried yet is no grease whatsoever. I think you might’ve mentioned well over a year ago something to that effect, and it always stuck with me. but every time decide to do that while working on a differential, I hesitate with ‘what the hell am I thinking’ running through my mind. But I will eventually. It would have to be a long-running test to see the effect on the gears themselves over several months.
 
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