Notorious Pinion Grub Screw

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knpc

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Arrma RC's
  1. Notorious
The grub screw on the pinion gear loosened during a run. It is a new truck, so it has never been removed.
The screw got mangled by spinning against the spur gear...any ideas on how to extract this?
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@knpc get yourself a decent screw extractor set and you should be able to get it out pretty easily.

Else you could very carefully drill it out.

Going forward, I would suggest anyone who buys any RC (new or used) to give it a very good look over and checking all the screws, nuts, gear mesh, etc.
 
The grub screw on the pinion gear loosened during a run. It is a new truck, so it has never been removed.
The screw got mangled by spinning against the spur gear...any ideas on how to extract this?
View attachment 49529View attachment 49530
Buy a Robinsons racing 16T and drill your grub screw out. Pay particular attention to your drill depth though...don't want to hit the motor shaft.
 
I can finally be of help here!
This exact same thing happened to me: new V4K out of the box, 4 packs into it and this happened after a grass run.
  1. Use a butane torch to heat that sucker up for 15+ seconds as there is a good amount of red loctite on there from factory. If you don't have that, a soldering iron on to the grub for a minute+ may work. Try not to heat the shaft and motor too much.
  2. Then use a screw extractor tool attachment on your power drill.
Note on costs: In my country it would have been quite a bit cheaper to go to my LHS and get them to do some surgical sawing to remove and replace the pinion.... (eg Pinion is NZD20 vs NZD50 for the extractor kit). Here the cost of that and replacing the pinion and grub is less than the cost of the screw-extractor set, butane torch and new grubs. But, hey, now I've got a set of screw extractors that I'll make good use of in future??

Also, there's a lip at the end of the motor shaft to make things a little trickier for you.... But it's logical why it's designed like that.

When replacing the grub, tighten it to the point you think your driver will twist/snap and make sure u use some Threadlocker. I failed to do it tight enough and I had to repeat the above.

Good luck.... and shout out to Cory Paterson on Fbook for guidance on this matter.
 

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I can finally be of help here!
This exact same thing happened to me: new V4K out of the box, 4 packs into it and this happened after a grass run.
  1. Use a butane torch to heat that sucker up for 15+ seconds as there is a good amount of red loctite on there from factory. If you don't have that, a soldering iron on to the grub for a minute+ may work. Try not to heat the shaft and motor too much.
  2. Then use a screw extractor tool attachment on your power drill.
Note on costs: In my country it would have been marginally cheaper to go to my LHS and get them to do some surgical sawing to remove and replace the pinion. Here the cost of that and replacing the pinion and grub is less than the cost of the screw-extractor set, butane torch and new grubs. But, hey, now I've got a set of screw extractors that I'll make good use of in future??
You make a great point about cost. For me it was cheaper to drill it out and replace it with the 16t from Robinsons Racing.

It all depends on what your current budget is for the repair.


Edit...in all honesty the best advice is to get the screw extractor kit...the grub screw looks like it backed out a lot.
 
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You make a great point about cost. For me it was cheaper to drill it out and replace it with the 16t from Robinsons Racing.

It all depends on what your current budget is for the repair.


Edit...in all honesty the best advice is to get the screw extractor kit...the grub screw looks like it backed out a lot.

Yah, looking back I would have been better off in the pocket to replace the pinion: Pinion is NZD20 vs NZD50+ for the extractor kit and more for the butane torch. Unfortunately, the expensive option was faster as a stock pinion would need to be ordered.
 
I was able to get the set screw out. Once I got the motor out, the screw was actually backed out so much that I was able to remove it with a small flathead.
I went through the truck out of the box, I checked a lot of screws...but missed that one.

I did notice there are two threaded holes on the pinion and a flat spot on both sides of the motor shaft. Any reason not to put two set screws in?

It was probably good that this happened. I noticed once the motor was out that the rear bearing on the center diff was shot. Only have 8 packs through it.
I'll pull the diff, replace bearings, and service it. I wanted to up the oil in the center diff anyway....I have 200k, 300k, and 500k. Leaning toward trying the 200k first.
 
Yah, looking back I would have been better off in the pocket to replace the pinion: Pinion is NZD20 vs NZD50+ for the extractor kit and more for the butane torch. Unfortunately, the expensive option was faster as a stock pinion would need to be ordered.
If there's red loctite on it from factory it shouldn't have come loose. Check it out well. Screw extracters wook well and definitely use a torch first but be careful not to damage anything from the heat... No more than 10 seconds or so for something that size. I actually have 3 extractor sets.. One from harbor freight... One from snap on tools and another from a company called eazy out I believe.
 
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