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Vintage Frog Rear End Grinding Noise

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Hi Everyone,

 

I am new to this site, new to RC but having a blast with it.  It is extremely addictive.  Anyways, I bought a beat up used frog. Hooked my transmitter up to it and it ran fine.  Of course, this was not good enough.  I purchased many hop ups.  I got all new parts for the gearbox, new gears, ball bearings, etc.  I built the gearbox.  I also got the 2005 Universal Shafts for it.  I followed the directions (in fact several times).  Without wheels on it, the gears are nice and tight, sounds smooth.  Once I put wheels on, I hear a grind.  This last time I put it back together, I left the boots off to try to see what is happening.  It appears that the Gearbox joints on both sides slide out of the gearbox, just slightly.  This is enough to make the swing shaft hit the slot in the gearbox joint everytime it rotates, making a grind noise.  Has anyone else run into this?

 

What makes this worse is I got so frustrated with it, I put the original hex shafts back on and now they do this as well.  Just so you know, The entire rear end is brand new, including the rear arms.  HELP!!!  Thanks.

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Hi again. Just pulled it apart again.  It does not appear to be doing what I thought.  It seems to be happening one I put the hub on.  It sounds/works great until this point.  I tried putting another set of bearings, but same thing.  Not sure why the hubs are making this terrible noise.  Going to se about putting the old hubs back on, see what happens.

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need photos and/or vids to understand, and be able to help out :)

 

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are you overtightening the rear wheel nuts as that can press the hubs into the  arm and bearing . try that first , then if it still does it try raising the rear arms up and turning the axles , if the noise stops it means you need to shorten the stroke of the damper by putting a spacer inside the damper to shorten the pistons travel at full extent , this is common in a few of the old Tamiya models - FAV , Wild One , Fox etc

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Hi Darat76, 

 

Thanks for looking at this.  Here is a video I just took, not sure how much it helps.  I took it at different stages of putting the left rear back together.  This time, when putting the hub on, I pressed on the shaft on the inside of the arm outwards which made the hub go on better/further.  After that, I noticed that it did not make the sound and thought I was done.  Then I put the wheel on and it did it again.  When I put both wheels on, and they both are going, it sounds pretty loud.  This was just the left sie.

 

https://drive.google.com/open?id=0B_HwsZkiGPthV1VJVWxtZEtzQTQ

 

Also, last night I tried to put the old hubs back on.  The diameter of the hole was too small to fit on these shafts so I could not try it.  Upon inspection, the hubs look identical.

 

Again, thanks for looking.

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that noise sounds like it's in the gearbox right at the start of that vid, it gets slightly more pronounced as you hook up the rest of the drive train, and really stands out once the wheel is on.

getting a tranny brace from @mheald might help with that, if he has any available for the hopper gearbox

 

so that you can understand, the wheel is acting like an amplifier for the sound by the weight and the shape of it, the cups and drive shaft are acting as transmitters of the sound out to the wheel by being metal, I often do something similar by using a large screwdriver, by pressing it against a 1:1 motor and sitting the handle just behind the earlobe, you can hear and track down the source of a noise in the motor, that works best with a big and long. hard plastic handled flat head screw driver.

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On 10/1/2016 at 2:55 AM, KEV THE REV said:

are you overtightening the rear wheel nuts as that can press the hubs into the  arm and bearing . try that first , then if it still does it try raising the rear arms up and turning the axles , if the noise stops it means you need to shorten the stroke of the damper by putting a spacer inside the damper to shorten the pistons travel at full extent , this is common in a few of the old Tamiya models - FAV , Wild One , Fox etc

Sorry, I did not see this.  I think you might be on to something here.  I have been busy with work so not a lot of time to wok on this.  I purchased the Brat gear that eliminates the two bevel gears and locks the axles.  I also purchased a piece that eliminates the rod where the upper gear goes through with a tube and screw to keep those metal outside plates together and not budge.  Also, sine I had to open it again, I cleaned it all and regreased as I was also thinking my greasing technique was lacking.  So after all of this, the gears sound good until the wheels are on.  After seeing your post, I backed the nuts off and the noise decreased, was still there but not as loud.  So I am not sure how to correct this as when I loosened the wheel nut then the wheel spins off the hub.  Any ideas?  Still not 100% sure this is it though but it is quieter.

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Try raising the arms as I suggested and tighten the wheels nuts so they don't spin off . You might have to fit new hubs if you have overtightened themas the pin may have pressed into the plastic on the back of the hub too much so not giving the correct spacing of hub from bearing in arm 

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Hi,

Did this issue ever get resolved?  I have exactly the same issue on an XB Frog I've just stripped down and rebuilt.

Everything sounds smooth until the hubs and wheels are back on.

Thanks in advance,

 

Jeff

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Sounds like the wheels were overtightened at some point, which deepened the recess for the drive pin in the back of the wheel hub adapter. Try switching the position of the pin in the X part of the adapter, put the wheel back on and try it. If that doesn't solve it, you can file the back of the adapter down some to keep it from hitting the trailing arm. If that doesn't work, try a known good set of adapters. I like to use the style with a separate metal hex drive so I can tighten the rear wheels as tight as I want to. Also make sure there's some heavy grease in the hex drives to keep the axles from bouncing around. And if all that doesn't work, the noise is probably coming from your gearbox.

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