Mojave New Mojave EXB does not roll smoothly - normal?

[atomos319]

I just got a new Mojave EXB. As I was starting to install my electronics, I noticed that the truck has a LOT of resistance to rolling. I am also noticing a "spot" where it nearly locks up if you push it along. With this, I have a visible wobble on the rear input cup. Bear in mind, NO motor has been installed yet.

This is my first EXB...is this normal? My regular Arrmas usually roll pretty freely when not connected to a motor. Is Arrma still having diff issues on the EXBs? Would you deal with this through Horizon or just take it back to the LHS for another one?

 

[Yas]

Remove the centre diff and centre driveshafts. Then when you roll it, you'll be able to tell which of the diffs (front or rear) has a mesh that is too tight, or both. Shim them accordingly at the diff bearings with the shims included in the manual packet

 

[Prowler666]

I

I just got a new Mojave EXB. As I was starting to install my electronics, I noticed that the truck has a LOT of resistance to rolling. I am also noticing a "spot" where it nearly locks up if you push it along. With this, I have a visible wobble on the rear input cup. Bear in mind, NO motor has been installed yet.

This is my first EXB...is this normal? My regular Arrmas usually roll pretty freely when not connected to a motor. Is Arrma still having diff issues on the EXBs? Would you deal with this through Horizon or just take it back to the LHS for another one?

Had a similar problem with kraton exb. Found out the plastic cover that fits over the cup was catching on the outside when it spins. I filed it a little and works fine now. Not saying it's the same issue though. Remove the shafts and spin the diff to find high spot.

 

[Woodley99]

I also has a similar problem on my kranton exb, the center diff housing was a bit tweaked, had to loosing up motor mount and diff mount and re tighten and all was well

 

[atomos319]

I

Had a similar problem with kraton exb. Found out the plastic cover that fits over the cup was catching on the outside when it spins. I filed it a little and works fine now. Not saying it's the same issue though. Remove the shafts and spin the diff to find high spot.

I suspect this might be my issue as well after thinking about that wobble on the cup- I wonder if just needs adjusted because it is rubbing.

I hate messing with diffs because I cannot tell what is a good mesh and what is a bad mesh, and I don't fully understand where I should be playing with the shims to improve any problems. I hope I don't have to tear open diffs on a brand new, never run truck.

 

[Prowler666]

That plastic bit is just a cover iirc. You don't need remove the diff.

 

[atomos319]

That plastic bit is just a cover iirc. You don't need remove the diff.

I know. I was saying I hope you are right because I would not be happy pulling the diffs (as suggested by Yas)

 

[atomos319]

Remove the centre diff and centre driveshafts. Then when you roll it, you'll be able to tell which of the diffs (front or rear) has a mesh that is too tight, or both. Shim them accordingly at the diff bearings with the shims included in the manual packet

Well, I removed the center diff and driveshafts. The rear spins freely, but the front appears to be snagging on the inside. I can feel the teeth of the pinion and planetary gear when it snags like this. It only happens when I spin the front two wheels together so that's how I know it's not internal to the diff. Nonetheless, I'm not sure how to fix this as again I am not very comfortable messing with shims. Maybe I am overthinking it; Any thoughts?

 

[Yas]

Well, I removed the center diff and driveshafts. The rear spins freely, but the front appears to be snagging on the inside. I can feel the teeth of the pinion and planetary gear when it snags like this. It only happens when I spin the front two wheels together so that's how I know it's not internal to the diff. Nonetheless, I'm not sure how to fix this as again I am not very comfortable messing with shims. Maybe I am overthinking it; Any thoughts?

The gears might just need bedding in, but QC on factory builds is often questionable, and I really would take this as an opportunity to tear down the build and check it all. I do this whenever I buy any RC anyway - down to the last screw. You probably won't want to go that far, but I would at least pull both the diff and the pinion

The best way to check your mesh is to have the bulkhead in your hands. There's plenty of YT vids explaining what to do. The shims you might need are included anyway. Don't worry about getting getting stuck in - it's all part of the game

 

[Prowler666]

check youtube for exb diff videos loads out there tbh, imo you are over thinking it, they are not that hard to work on once you seen a vid or two.

 

[Woodley99]

Agree with what @prowlerand @Yas said above. Don't be afraid to take her apart, there's plenty of YouTube vids that break it down step by step, working on these rigs is half the fun in my opinion
Honestly you'll need to get familiar with it also, tearing down diffs and rebuilding with fluid shims etc. is a normal part of maintenance with this level of RCs. We all were afraid to tear it down at one point but as soon as you do it once you'll be comfortable and want to tackle more things. All part of the fun! Don't be afraid to ask questions just like your doing with this one, their are many people better than myself to help you along the way your already on the right track by questioning someone that doesn't seem right, alot of people (like my younger brother haha) run it till it won't run no more and you have WAY more issues than you started with.
Good luck and keep us posted

 

[atomos319]

Agree with what @prowlerand @Yas said above. Don't be afraid to take her apart, there's plenty of YouTube vids that break it down step by step, working on these rigs is half the fun in my opinion
Honestly you'll need to get familiar with it also, tearing down diffs and rebuilding with fluid shims etc. is a normal part of maintenance with this level of RCs. We all were afraid to tear it down at one point but as soon as you do it once you'll be comfortable and want to tackle more things. All part of the fun! Don't be afraid to ask questions just like your doing with this one, their are many people better than myself to help you along the way your already on the right track by questioning someone that doesn't seem right, alot of people (like my younger brother haha) run it till it won't run no more and you have WAY more issues than you started with.
Good luck and keep us posted

I am not new to RCs and I have replaced and taken apart diffs before. I have replaced spider gears. I just hate doing it, and I feel like I should not have to do it for a brand new, never run truck. I appreciate the kind words either way.

so I have narrowed it down to the front differential . The truck is smooth when it's out (other than the bent from the factory drive shafts... don't get me started) but grinds like a blender when I put it back in. There is zero play with it, no room for a shim. I opened it up and found it dry, so I added 10k fluid, still grinds badly. So now I am completely out of ideas. Is it possible they put the wrong pinion in it? I think the front and rear are different part numbers. But I don't know how I could tell visually as they look the same and are both 10 tooth I think. Do I need to replace the diff box...maybe this one is too tight? Any ideas?

This truck has got me so pissed off. Broke as poop straight from the factory.

 

[Yas]

I am not new to RCs and I have replaced and taken apart diffs before. I have replaced spider gears. I just hate doing it, and I feel like I should not have to do it for a brand new, never run truck. I appreciate the kind words either way.

so I have narrowed it down to the front differential . The truck is smooth when it's out (other than the bent from the factory drive shafts... don't get me started) but grinds like a blender when I put it back in. There is zero play with it, no room for a shim. I opened it up and found it dry, so I added 10k fluid, still grinds badly. So now I am completely out of ideas. Is it possible they put the wrong pinion in it? I think the front and rear are different part numbers. But I don't know how I could tell visually as they look the same and are both 10 tooth I think. Do I need to replace the diff box...maybe this one is too tight? Any ideas?

This truck has got me so pissed off. Broke as poop straight from the factory.

Did you loosen the diff input cup and remove the pinion? The front and rear should be the same 10t and read GP4 on the shaft. Maybe the bearings aren't fully seated? I would rebuild this bit too

I think the GP4 diffs have a tighter mesh by design. They seem to sit slightly wider at the bearings than the RTR diffs. I'll guess at around 0.2 to 0.4mm. It left me much less room for shims than it had done for my RTR diffs

Maybe it'll just need bedding in after a few runs. My EXB diffs were a bit tight - there was a small but noticeable amount of rolling resistance even after I rebuilt the bulkheads. They definitely loosen up over time. However it shouldn't be too notchy at certain degrees of the rotation to the point it becomes tight to turn the input cup lightly with a finger and a thumb

I guess if it can't be resolved you could get hold of your seller and exchange it