Kraton Darn Dif pins

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, and others.

FatCatRC

FatCat Team Racing
Build Thread Contributor
Messages
2,354
Reaction score
3,182
Arrma RC's
  1. Kraton 6s
  2. Notorious
So 2nd time in 3 runs I have broke a front dif pin and maybe a sun gear again(haven't looked yet). My front right on both times. Lmao she spins free right now and it shouldn't do that. I have one spare left until my stonger set comes in. What would cause it to snap the pin twice in such a short time. I was just ripping on the street and a cpl small 2 -4 high jumps. I got stock copper heads and put the stock arms on. I have 500k in centre, 50k rear and 70k front for dif lube. I am running a 4985 1650 on 19t with a stock spur 6s battery. Punch is at lowest on a max6. is it just weak armma stock gears or am I driving like an idiot, or is it the big can with it's monster tourque chewing my dif?
 
Lower the diff fluid weight.. less shock will be put into the pin and gear on whichever side touches down first.. ?
 
This is driver error. On landing you need to be off the throttle/brake.
You could try better pins. These will fit but you would have to cut to length. I'm running 50/500/50 and haven't had issues with breaking pins.

Stock is 2.25mm

 
Last edited:
This is driver error. On landing you need to be off the throttle/brake.
You could try better pins. These will fit but you would have to cut to length. I'm running 50/500/50 and haven't had issues with breaking pins.

Stock is 2.25mm
McMaster Carr
2900A241Hardened Undersized High-Speed M2 Tool Steel Rod, 2.300 mm Diameter, 2-1/4" Long
Okay sorry, I'll be more clear. I was NOT jumping the car the first time it snapped the pin and gear. The second time (today) I was jumping the car maybe 4 feet high in the air, I was not on the throttle when it landed at all. I was just saying i have done it by mistake before but NOT today. I was recommended the weight dif fluid I use by a few other people and I have read a lot of people run that setup without issues.
 
The 50k in the front will soften the load.. you are popping them quite quickly, how are the bores in the cups? Can you slide the cup out freely? or does it bind on the way out? If you feel a bind on the way out the cup bores are shot.. this will contribute a bunch to broken pins as well..
 
Well got the motor and center dif out....I'm I guessing a rock got jammed up in there cuz well the picture says it all.
 

Attachments

  • 1594609909568377022158.jpg
    1594609909568377022158.jpg
    271.9 KB · Views: 60
The one side was hard to get out yes.i have all new gears and metal cases coming. The gearbox is aluminum too. The sun gear seamed a bit sloppy too.


Ya the bore is wollered out.. it peens the edge of the bore making the o.d of the cup shaft larger than the cup/ring gear bores.. this just introduces extra slop/snap.. I would replace the cups if you can..

Sucks about the center diff.. I've seen people post similar pictures of the centers ground up.. I've yet to have that happen to me.. (knock on wood)..??
 
Ya the bore is wollered out.. it peens the edge of the bore making the o.d of the cup shaft larger than the cup/ring gear bores.. this just introduces extra slop/snap.. I would replace the cups if you can..

Sucks about the center diff.. I've seen people post similar pictures of the centers ground up.. I've yet to have that happen to me.. (knock on wood)..??
The cups are brand new though? I got them last week. And the dif itself isn't that old either maybe 10 5 minute runs with it. I break too much stuff to run it for long lol.
 
Dishing out the abuse over there.. ??..
Man I break something every run, lately it's my servo taking a crap. Two gear sets now and this ones on it's way out. I can't wait for my new servo in the mail. I have to wiat for my order to come in the mail with all my new dif gears and spare cups, I'm gunna try them and see if it makes a difference.
 
I heard 2.6 fit as well. And to get titanium rod or blanks. I'll have to look better on eBay. In my hick town we don't have cool things like that. I have to order everything.
 
@LibertyMKiii Those are not the diff pins. They go in the hub and have a different diameter.
Diff pins are 2.25mm but 2.5mm will not. The 2.3mm ones will fit.
Thanks for pointing that out for the others.
Never done it myself, as mentioned I pulled that from another users build thread
The key takeaway is quality drill bits are a low cost method of getting better metal to replace the pins.
 
Correct, drillbits will work. You can get 1 pin out of 1 bit, keep that in mind when ordering drill bits.
2.6 will not fit anywhere, at far as I know. You could potentially drill it out but that would weaken the rest of the assembly and will serve no purpose.
2.3 (max) for diff
2.5 for the hubs and 4mm for hinge pins. Thats all there is on an Aarma.
 
Well ladys and germs, it turns out I broke a drive cup. The pin and sun gear were intact but the drive cup split at the hole. I am going to lower dif fluid weight and see if that helps when new gears get here. Also I ask again does anyone know what the damn set screw is for in the top gearbox cover for a hot racing gearbox/cover. That set screw ended up in the gearbox the last time the pin broke and chewed my stock bearing and left a nice gouge in the dif case.
 
Well ladys and germs, it turns out I broke a drive cup. The pin and sun gear were intact but the drive cup split at the hole. I am going to lower dif fluid weight and see if that helps when new gears get here. Also I ask again does anyone know what the damn set screw is for in the top gearbox cover for a hot racing gearbox/cover. That set screw ended up in the gearbox the last time the pin broke and chewed my stock bearing and left a nice gouge in the dif case.


It's for the typhon.. the piece of body screws to it.. we run the plastic cases with no screw in it.. if your content with the screw idea I would use a button head so it can only fall out not in.. otherwise ditch the screw...?
 
Old Thread: Hello . There have been no replies in this thread for 90 days.
Content in this thread may no longer be relevant.
Perhaps it would be better to start a new thread instead.
Back
Top