Big Rock Diff case gear and input gear stripped. Why?

[Ragga]

Big tires and normal wear. For a point of reference, I probably ran 25 packs through my BRCC before it gave up a diff running Granite wheels and loads of jumps.

Ok good to know thanks!

 

[parcou]

Ok good to know thanks!

I keep a spreadsheet on my runs for my Big Rock. I have never touched my slipper just did not want to scary to me. 35 packs later I did open it and it looked good there was no issue and no need to open it. The only reason I opened it I wanted to make a change I will not discuss here to stay on topic.

I agree with the user that posted on the HR yokes. Not agreed with other users but those metal yokes around the diff stopped the flexing for me and eating the input gear (which can save your spur).

Regardless of what you do in your repair, personally, I am in favor of HR yoke for the rear only because the plastic yoke allows movement under stress and can lead to issues you are seeing. My $0.02

https://www.amazon.com/gp/product/B07MPZCTK2/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

 

[Ragga]

I keep a spreadsheet on my runs for my Big Rock. I have never touched my slipper just did not want to scary to me. 35 packs later I did open it and it looked good there was no issue and no need to open it. The only reason I opened it I wanted to make a change I will not discuss here to stay on topic.

I agree with the user that posted on the HR yokes. Not agreed with other users but those metal yokes around the diff stopped the flexing for me and eating the input gear (which can save your spur).

Regardless of what you do in your repair, personally, I am in favor of HR yoke for the rear only because the plastic yoke allows movement under stress and can lead to issues you are seeing. My $0.02

https://www.amazon.com/gp/product/B07MPZCTK2/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

Ok great. Thank you!!

 

[JPWSRC]

For reference. This will help keep alignment proper for sure. Never a thought on my 3s BRCC and Typhon, but definitely necessary on the rear diff on my 4s Kraton and Outcast. I'm using 12x16x0.1 shim on the crown side. Mesh is nice.

 

[AverageWhiteGuy]

For reference. This will help keep alignment proper for sure. Never a thought on my 3s BRCC and Typhon, but definitely necessary on the rear diff on my 4s Kraton and Outcast. I'm using 12x16x0.1 shim on the crown side. Mesh is nice.

View attachment 212988

Yep.

 

[Ragga]

For reference. This will help keep alignment proper for sure. Never a thought on my 3s BRCC and Typhon, but definitely necessary on the rear diff on my 4s Kraton and Outcast. I'm using 12x16x0.1 shim on the crown side. Mesh is nice.

View attachment 212988

View attachment 212989

That looks nice. Ok good to know. Anybody have video of a good alignment? I’m sure there is one on YouTube somewhere. I can check. But if you have a vid let me know. Thank!

View attachment 213110 Yep.

 

[L3phturn]

Today I learned that TRB RC also has shims! Awesome. I haven't needed the HR yoke yet, but it's good to know there is a strong solution if needed.

 

[JPWSRC]

Today I learned that TRB RC also has shims! Awesome. I haven't needed the HR yoke yet, but it's good to know there is a strong solution if needed.

Glad to be of service.

 

[parcou]

Spot on JPW... as well as a shim on the crown side for that good mesh.

 

[JPWSRC]

Spot on JPW... as well as a shim on the crown side for that good mesh.

You may call me JP.
Realizing my forum name is a PIA.

 

[f_noggle]

That's the Arrma life.

 

[Ragga]

I put together the new rear input and diff case. Now it’s binding when I tighten the yoke. Does it need to break in a bit to get smoother?

 

[Hector_Fisher]

I put together the new rear input and diff case. Now it’s binding when I tighten the yoke. Does it need to break in a bit to get smoother?

In my experience no, that doesn't work. It needs to be meshed right from the beginning. If there are interferences in the gears when they run it's just going to stress the teeth and eventually break them (if the binding is bad). Did you shim?

Couple of other thoughts
https://www.arrmaforum.com/threads/rebuilt-diff-issues.33207/

 

[Velodromed]

I put together the new rear input and diff case. Now it’s binding when I tighten the yoke. Does it need to break in a bit to get smoother?

I sand/carve any bad uneven spots and shim the diff. Also make sure the bearings are seated well on the diff. I use a socket and rubber mallet. Also, if the diff is new I’ll put the shim opposite the ring gear. If it’s broken in Ill remove the shim or put it on the ringside as necessary.

 

[Ragga]

In my experience no, that doesn't work. It needs to be meshed right from the beginning. If there are interferences in the gears when they run it's just going to stress the teeth and eventually break them (if the binding is bad). Did you shim?

Couple of other thoughts
https://www.arrmaforum.com/threads/rebuilt-diff-issues.33207/

Ok. Thanks for the info. I just read the thread you sent. Seems people are mentioning it might have to wear in a bit. Not sure. Also about shims. I really can’t find anything on where to shim. People say it on threads but I’m not understanding how to do it with out seeing it.

I sand/carve any bad uneven spots and shim the diff. Also make sure the bearings are seated well on the diff. I use a socket and rubber mallet. Also, if the diff is new I’ll put the shim opposite the ring gear. If it’s broken in Ill remove the shim or put it on the ringside as necessary.

I’m not understanding where to shim. I’m not sure if it really needs it though. Bearings seem fit fine. I put it together and took a part many times. I guess I just have to not tighten the yoke fully. When I back off it looses and spins better.

 

[PeighDay]

For reference. This will help keep alignment proper for sure. Never a thought on my 3s BRCC and Typhon, but definitely necessary on the rear diff on my 4s Kraton and Outcast. I'm using 12x16x0.1 shim on the crown side. Mesh is nice.

I also have the HR yokes. I had to put two shims on the gear side of the diff.100x better than those plastic diffs.

 

[Hector_Fisher]

Ok. Thanks for the info. I just read the thread you sent. Seems people are mentioning it might have to wear in a bit. Not sure. Also about shims. I really can’t find anything on where to shim. People say it on threads but I’m not understanding how to do it with out seeing it.

I’m not understanding where to shim. I’m not sure if it really needs it though. Bearings seem fit fine. I put it together and took a part many times. I guess I just have to not tighten the yoke fully. When I back off it looses and spins better.

Shimming is a process of trial and error. It's used to account for differences between the same part that comes off the manufacturing line slightly different than the one before and the one after. That's how you get proper gear mesh.

If your diff is binding, meaning the gears are hard to spin all the way around, no amount of self clearancing (wearing in) will make it right. If the gears roll well but sometimes hit a snap, check for bad teeth or debris, but usually those are the types of "binding" that I would let self-clearance (wear in).

Shimming is just finding the right combination/ placement of spacers to make it so the gears move closer or farther to each other and set the proper mesh.

This is a good video for the physics of meshing gears and how to "feel" for mesh

 

[GRC]

I put together the new rear input and diff case. Now it’s binding when I tighten the yoke. Does it need to break in a bit to get smoother?

Try these steps, in this order:
1) The differential comes with one shim (washer) underneath one of the differential bearings. From the factory it is underneath the bearing on the gear side of the differential. When you put the shim on the gear side, it makes the mesh tighter (it pushes the differential gear and input gear closer together). If you put it on the opposite side, it makes the mesh looser (it pushes the differential gear and input gear further apart). Try loosening the mesh if you're binding. I've never had to use more than the one shim.
2) Make sure the bearings on the sides of the differential are pushed all the way on. They are a tight fit. I usually have to hammer them a bit to get them all the way on. I use an adjustable wrench. Open it up enough to touch only the bearing. Then hammer on the wrench to push the bearing down.
3) The two sides of the yoke are not identical. One side has a small tab on the inside. Put this on the opposite from the differential gear. Otherwise, it will rub the back of the gear.
4) Dirt, debris, excessive grease can cause binding. Clean off the gears. Use a thin coat of grease.
5) The differential yoke can get warped. A warped differential yoke can cause binding. If none of the above work. Try a new differential yoke. (I've even had a differential case/gear get warped, but yours is new, so that's probably not the problem)

 

[Ragga]

Try these steps, in this order:
1) The differential comes with one shim (washer) underneath one of the differential bearings. From the factory it is underneath the bearing on the gear side of the differential. When you put the shim on the gear side, it makes the mesh tighter (it pushes the differential gear and input gear closer together). If you put it on the opposite side, it makes the mesh looser (it pushes the differential gear and input gear further apart). Try loosening the mesh if you're binding. I've never had to use more than the one shim.
2) Make sure the bearings on the sides of the differential are pushed all the way on. They are a tight fit. I usually have to hammer them a bit to get them all the way on. I use an adjustable wrench. Open it up enough to touch only the bearing. Then hammer on the wrench to push the bearing down.
3) The two sides of the yoke are not identical. One side has a small tab on the inside. Put this on the opposite from the differential gear. Otherwise, it will rub the back of the gear.
4) Dirt, debris, excessive grease can cause binding. Clean off the gears. Use a thin coat of grease.
5) The differential yoke can get warped. A warped differential yoke can cause binding. If none of the above work. Try a new differential yoke. (I've even had a differential case/gear get warped, but yours is new, so that's probably not the problem)

View attachment 213815

Oh wow thank you! I will go over all of this.

Shimming is a process of trial and error. It's used to account for differences between the same part that comes off the manufacturing line slightly different than the one before and the one after. That's how you get proper gear mesh.

If your diff is binding, meaning the gears are hard to spin all the way around, no amount of self clearancing (wearing in) will make it right. If the gears roll well but sometimes hit a snap, check for bad teeth or debris, but usually those are the types of "binding" that I would let self-clearance (wear in).

Shimming is just finding the right combination/ placement of spacers to make it so the gears move closer or farther to each other and set the proper mesh.

This is a good video for the physics of meshing gears and how to "feel" for mesh

Awesome. Thank you I will check it.

I haven’t had issues since getting the hot racing diff yokes and good bearings. I use red n tacky grease. We run 4s

Did you have to shim with the HR yokes?

 

[JPWSRC]

Ok. Thanks for the info. I just read the thread you sent. Seems people are mentioning it might have to wear in a bit. Not sure. Also about shims. I really can’t find anything on where to shim. People say it on threads but I’m not understanding how to do it with out seeing it.

I’m not understanding where to shim. I’m not sure if it really needs it though. Bearings seem fit fine. I put it together and took a part many times. I guess I just have to not tighten the yoke fully. When I back off it looses and spins better.

What yoke are you using? The composite yoke should not need to be cranked down, just snug. The shim we're talking about on a new stock diff is installed between the outer output bearing and the diff case,

Oh wow thank you! I will go over all of this.

Awesome. Thank you I will check it.

Did you have to shim with the HR yokes?

Yes to the last question, in my case it was opposite the crown gear. Lately the pre-assembled Arrma diffs have been coming with the shim on the opposite side of the crown gear. Did you use a composite yoke or metal one?