Center diff spur gear rubbing on the chassis

[-Dusty-]

I shimmed and filled my center diff yesterday and everything seemed ok but then I noticed that the spur gear is too far forward and slightly rubbing on the chassis. Has anyone had this problem before?

Would a shim or two help on the plastic diff holder thing? I don't really want to run it like this if it can cause more problems later

 

[-Dusty-]

I took it apart, noticed some gunk in the motor mount behind bearing. Thought that was it.

Put it back together and snugged everything up. The spur was centered. Took it out for a little run and it slowly went forward.

So there is some movement somewhere. Could it be that plastic diff holder?

Also thinking it could be from the motor mount screw hole. I had to drill out a screw when I stripped it. When I drilled it I shaved a tiny bit off the chassis hole. Not sure how to describe it. Maybe the cause.

 

[-Dusty-]

Im 85% sure its the plastic diff mount. Think the screw holes are stripped because I tighten those screws and everything centers up. After a quick run it moved forward.

After the run I tighten a little bit and it moved back.

Can I use krazy glue for a temp fix to keep the screws tight?


On a unrelated note, I have my first breakage today. Snapped the screws that held in the front stock bumper.

 

[ThatDrewGuy]

I have used a little bit of blue Threadlock on some plastic parts. Seems to hold pretty darn well.

 

[-Dusty-]

I'll try that out. Thanks!

 

[olds97_lss]

CA Glue works better on plastic. But it's a very temporary fix.

 

[bicketybam]

https://www.amainhobbies.com/hot-ra...A0SGXMITeY607Y3RdKlFV0RBV_DJQw1kaAiNjEALw_wcB

Problem solved.

 

[olds97_lss]

https://www.amainhobbies.com/hot-ra...A0SGXMITeY607Y3RdKlFV0RBV_DJQw1kaAiNjEALw_wcB

Problem solved.

Just an FYI, don't try going cheap and buying a new OEM motor mount off ebay, then cutting off the motor part to use the rest for the front side of the diff. I tried that... the back side of the brace is milled to a different depth than the front side, so when you install a second back side on the front side of the diff, it's not wide enough.

I stripped my front X piece like you did. So, I ordered an entire mount/x piece on ebay for $11. Then when I got it, I had the bright idea of cutting off the motor mount piece and using the remaining piece on the front side of the diff. It didn't work, so I basically destroyed a motor mount. I did end up using the new plastic piece that came with it, so it wasn't at total loss.

That was on my outcast.

 

[chevys10zr2003]

https://www.amainhobbies.com/hot-ra...A0SGXMITeY607Y3RdKlFV0RBV_DJQw1kaAiNjEALw_wcB

Problem solved.

Another common mod is to get a motor mount and cut off the motor mount side. Cut off everything circled in blue in the picture below.

https://jennysrc.com/collections/ar...m-red-mount-motor-center-diff-kraton-ar106021

Edit:
I guess it didn't work out so well for @olds97_lss lol. As he was typing at the same time that I was.

 

[olds97_lss]

Another common mod is to get a motor mount and cut off the motor mount side. Cut off everything circled in blue in the picture below.

https://jennysrc.com/collections/ar...m-red-mount-motor-center-diff-kraton-ar106021

View attachment 21489

Edit:
I guess it didn't work out so well for @olds97_lss lol. As he was typing at the same time that I was.

That didn't work on my outcast. It made the gap too small and I couldn't put my diff in without causing serious binding on my center diff bearings.

It's off like 1mm or so. Just enough to crunch down on the bearings. When I installed it and gently tightened the screws on both pieces, the front/rear mounts looked like \ /

 

[ThatDrewGuy]

My problem with those diff mounts is that more than once, with only a little bit of thread lock, I have gotten 2 screws stuck in them. Had to drill it off the chassis, and they were a loss. Totally irritated me...

 

[olds97_lss]

My problem with those diff mounts is that more than once, with only a little bit of thread lock, I have gotten 2 screws stuck in them. Had to drill it off the chassis, and they were a loss. Totally irritated me...

With something like that, I cut a notch in the screw and use a flat blade screwdriver. Sure, it will notch the chassis a little bit, but with a new disk on my dremel, you can mostly just notch the screw with a deep enough notch to get it out.

Also, if it feels like it's going to strip, you can use a pencil torch or soldering iron to cook the screw which melts the threadlock, then you can usually back them out. Granted, I rarely figure that out before it's stripped... so I end up with notches in my chassis. What's a few more cuts in the bottom of a chassis anyway? After driving my truck for 10 minutes, the bottom gets all scratched up anyway.

 

[joostin420]

@bicketybam is right. its an investment but I can tell you firsthand it is bulletproof.

 

[JMS RC]

Just an FYI, don't try going cheap and buying a new OEM motor mount off ebay, then cutting off the motor part to use the rest for the front side of the diff. I tried that... the back side of the brace is milled to a different depth than the front side, so when you install a second back side on the front side of the diff, it's not wide enough.

I stripped my front X piece like you did. So, I ordered an entire mount/x piece on ebay for $11. Then when I got it, I had the bright idea of cutting off the motor mount piece and using the remaining piece on the front side of the diff. It didn't work, so I basically destroyed a motor mount. I did end up using the new plastic piece that came with it, so it wasn't at total loss.

That was on my outcast.

Another common mod is to get a motor mount and cut off the motor mount side. Cut off everything circled in blue in the picture below.

https://jennysrc.com/collections/ar...m-red-mount-motor-center-diff-kraton-ar106021

View attachment 21489

Edit:
I guess it didn't work out so well for @olds97_lss lol. As he was typing at the same time that I was.

That didn't work on my outcast. It made the gap too small and I couldn't put my diff in without causing serious binding on my center diff bearings.

It's off like 1mm or so. Just enough to crunch down on the bearings. When I installed it and gently tightened the screws on both pieces, the front/rear mounts looked like \ /

I bought into that mod as well, really thought it was a piece of cake until i tried to install it.
I don't really have access to a mill so i decided to do it by hand, took off about 1.5mm on the side towards the diff and bored out the inside bearing edge about the same. Fits nicely now but the amount of time spent it would be better to just order an aftermarket one, even if this would mean to wait a week before it arrived. I have noticed that even the stock setup have some play front to back, used a 13x16 shim to minimize that play.

A setup I bought for my Talion, the sturdiest one I own yet. Had to shim this one as well. The only downside with having the front mount in alu is the amount of noise it transfers to the chassi, might be why Arrma decided to use a plastic one.

 

[olds97_lss]

Yeah, I don't have the tools or ability to do that kind of a mod well enough to not cost me bearings. What brand is that top cap you used? Looks beefy.

They probably just use plastic to keep cost down. Metal on metal gears are pretty noisy regardless of the mount.

 

[JMS RC]

Sure, it might be to keep the cost down, but mine is much noiser now. The top cap and front diff mount is made by Michael Meyer at MMM-Germany Custom Rc Parts And More, reachable through Facebook. He makes various parts, all top notch.

Here's a little better view

 

[-Dusty-]

https://www.amainhobbies.com/hot-ra...A0SGXMITeY607Y3RdKlFV0RBV_DJQw1kaAiNjEALw_wcB

Problem solved.

Ordered!

 

[-Dusty-]

Woke up early so I figured I would install it. Got the top brace as well because why not.

One thing I did notice is that there is zero play. Its almost too tight. I got fast eddy bearings in there so not sure if that makes a difference. Not sure if they are a bit wider than the stock bearings. Its been real wet here so not sure if I can test it out today, but I think this is going to fix my problem with the movement. I just hope it doesn't add a problem with the bearings

 

[JMS RC]

Woke up early so I figured I would install it. Got the top brace as well because why not.

One thing I did notice is that there is zero play. Its almost too tight. I got fast eddy bearings in there so not sure if that makes a difference. Not sure if they are a bit wider than the stock bearings. Its been real wet here so not sure if I can test it out today, but I think this is going to fix my problem with the movement. I just hope it doesn't add a problem with the bearings

View attachment 21689

Nice. Just do a 10 minute run on a 4S and check for play again. The play on mine increased a tiny bit after doing that.

 

[-Dusty-]

Did a small run, no play. Which imo is good right now because my spur is still sitting forward quite a bit. Its not grinding the chassis anymore but if there was play, it probably would.

I really hope its not because of the chassis. That time I had to drill out a screw and chipped a lil off that hole on the chassis. But the screw is not really off balance or anything like that so I don't think it would have this much play.

I don't know. Might take it apart again and see.