Kraton Rear diff bearing popping off after 15 minutes

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luisthehippy

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Arrma RC's
Hi everyone,

First of all, thanks to everyone in this forum, I've bought my first RC car after years of wanting one, and have had it since Christmas. My Kraton V3 has been incredibly fun to bash, and upgrading it has been really enjoyable. Since it's my first RC, the info here has been invaluable, so thank you!

Since it's my first RC, apologies if this is a simple question, but here's my issue: what is the rear diff bearing held in place by? I'm talking about the one that is around the in-gear from the driveshaft. By that I mean, is the dogbone diff cup the only thing holding the bearing in?

While I was driving the car, the grub screw came loose, and I didnt get any power to the wheels. After reinstalling the grub screw with loctite, the bearing came off again after 15 mins driving, and I found the grub screw loose again. I'm not sure if I didnt put enough loctite (since the grub screw came loose again, and I think letting the bearing pop out again), I didnt let the loctite sit for enough time (about an hour) or I have a bigger issue. Although, If I push the bearing back in by hand, it seems to work.

Thanks again for all your help, and apologies if I used some terminology incorrectly.
Luis

20190711_151241.jpg
 
You are correct that nothing really holds the bearing in other than the drive cup being there in the way.

Few things to consider/look at:

1. Pull the set screw completely and look at it. Is the surface of the set screw that does the "holding" still flat? (might need to be replaced)
2. Loctite typically takes a long time to set/dry, something like 12-24 hrs.
3. Use a high quality hex wrench like MIP and tighten it real good.
 
Hi Everyone,

Thanks so much for the replies. I took out the grub screw and a portion of the flat area was chipped off. I just put in an order for a set of new ones.

Also, when that comes in, I'll put a little more loctite and set it for a good 24 hours. I just bought some MIP drivers, which I'm loving! I might also do the bearing since it'll take a while for the grub screws to get here.

Thanks so much, everyone! I'll report back, and have a good one.
Luis
 
The MIPS are great. Have a look at the bearing before you replace it, If it is too gritty to clean up then Yes replace it otherwise. I lift my seals, hit it with RP7 or WD40 if not too gritty, then let them dry, pack with grease and reseal. Something about throwing a way good stuff regardless how cheap, that just doesn't work for me
 
The MIPS are great. Have a look at the bearing before you replace it, If it is too gritty to clean up then Yes replace it otherwise. I lift my seals, hit it with RP7 or WD40 if not too gritty, then let them dry, pack with grease and reseal. Something about throwing a way good stuff regardless how cheap, that just doesn't work for me
What kind of grease you use?
 
I will add that the photo above shows the drive cup not up against the bearing. that's kind of what holds it in place.
 
I just use a red grease that is suitable for bearings. I can't remember if it is from Nulon or Penrite but I can have a look when I get home if you want to know precisely?
No, that's ok. I think I should be able to find something that will work. I have tried bearing oil from the hobby store but it seems like it is just way too thin because most of it leaks out.
 
a note on the TL; a habit I've gotten in to is to clean the screw with brake cleaner or electronics cleaner to remove any manufactures oils so the TL will hold better. let that dry well and always a solid 24hrs cure time on the TL.

good luck on your grub screw
 
Tour problem is not on the bearing. I had the same problem on another vehicle. I replaced the grub, the input pinion, loctited the grub with ridiculous amount and let it cure properly, replaced the bearing... And the cup still got loose. The problem is the cup. In my case, the cup hole didn't offer any friction when I was screwing the grub, so I thought the threads should probably be deformed/expanded. Replaced the cup, loctite on the grub and solved my problem...
 
Hi everyone,

Thought I'd update since it's been a while. So, I ordered new grub screws, put a little more than a dab of blue loctite and let it set 24 hours. I haven't had a problem since. I'm guessing I didn't let it set long enough the first time (about 1 hour). I was surprised by how small the chip was on the edge of the screw, but that's all it took to prevent the cup from slipping out of the input gear.

Thanks again for everyone's help! Happy bashing.
Luis
 
Glad to know! That problem annoyed me so much... Be aware that the hole in the screw may also become loose. But usually the cups have two threaded hole...
By the way @luisthehippy are you Portuguese? ?
 
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