Big Rock Making a stronger rear diff...broken again. What am I missing here?

[parcou]

Help

You all have been great to get me along with my BR BLX rear diff post. I do run the CVDs for the belted MX28 Badlands 2.8" and this install was a new crown gear and new input gear the OEM version for the latest BR v3. I also have the HR yoke on it installed at the same time with crown/input and the crown/input gear look good on wear. I have about 5 battery packs on all these when this happened.

The internal rear diffs are at a total life of about 40ish packs... Bashing I heard the rear diff spinning internally. Took it apart and found this. My question what would have caused the diff outdrives to eat up just one side? Is this a shimming issue INTERNALLY or just age and wear/tear?

Just for reference there is no shim on the crown side but again all was meshed well...

@Edough13 @jondilly1974 @SrC

 

[Surchaufeur]

In 2 years i still have the original internal gears
I would say the rubber sealed bearing inside the diff is the problem i never changed mine

 

[jondilly1974]

I have never broken internal 3S/4S gears

 

[parcou]

In 2 years i still have the original internal gears
I would say the rubber sealed bearing inside the diff is the problem i never changed mine

Thx for the reply...

When I put the new crown gear in, input, and HR yoke in I did change the diff which I use better aftermarket... interesting on this one for the rookie here

I have never broken internal 3S/4S gears

Thx Man....damn not the way I would like to have one up on ya...LOL
Upon further looking at the other gears....I have been doing something....

 

[Edough13]

I'm wondering if it's when you put it back together it wasn't all aligned right. I just did mine last night as I just went to the CNC crown gears and inputs which require a new cups also. Anyways I had one give me a lot of trouble I'd get it together and would spin like it was supposed to then all of a sudden would only spin about 180°. I had to take it apart and put it back together a few times before the pins and gears lined up right and it finally stopped doing it. So wondering if yours did the same and when you first checked was fine but then like mine would lock halfway after a few spins. Just very odd it would spin half way in either direction and then stop and lock up at one spot after spinning fine first few times. Just a possibility or just from age they finally gave or you had a rock get stuck between the driveshaft and A arm and the other side spun hard and snapped the gears on the side that couldn't spin?

 

[Camaroboy383]

I think the pins were not seated in the top cap bores properly.. clean out the cup and cap, and post pictures of the cup and cap empty.. you can clearly see one pin bore on the cap is blown out..

That bore is likely the one that was not seated, you should be able to see that in the lower cup bore once clean if in fact the pin was not seated in the cap..

 

[parcou]

I think the pins were not seated in the top cap bores properly.. clean out the cup and cap, and post pictures of the cup and cap empty.. you can clearly see one pin bore on the cap is blown out..

That bore is likely the one that was not seated, you should be able to see that in the lower cup bore once clean if in fact the pin was not seated in the cap..

Wow....look at this....you are on it....if I put the cap on and screwed it down how would this come up....top cap the pin holes are cut out like pulled to a side

 

[SrC]

I think the pins were not seated in the top cap bores properly.. clean out the cup and cap, and post pictures of the cup and cap empty.. you can clearly see one pin bore on the cap is blown out..

That bore is likely the one that was not seated, you should be able to see that in the lower cup bore once clean if in fact the pin was not seated in the cap..

^^^ This.

 

[Camaroboy383]

Wow....look at this....you are on it....if I put the cap on and screwed it down how would this come up....top cap the pin holes are cut out like pulled to a side

View attachment 170064View attachment 170065

Yeah, I can confidently say that the pins were not seated properly in the bores..

 

[parcou]

Yeah, I can confidently say that the pins were not seated properly in the bores..

@Camaroboy383 @SrC

Thx...seems the pic posted or not posted.... but I am lost if I screwed the top those how the pins could move....I agree this happened just now a loss of confidence now when I close the diff back up again, LOL

 

[Keithaseelye]

Help

You all have been great to get me along with my BR BLX rear diff post. I do run the CVDs for the belted MX28 Badlands 2.8" and this install was a new crown gear and new input gear the OEM version for the latest BR v3. I also have the HR yoke on it installed at the same time with crown/input and the crown/input gear look good on wear. I have about 5 battery packs on all these when this happened.

The internal rear diffs are at a total life of about 40ish packs... Bashing I heard the rear diff spinning internally. Took it apart and found this. My question what would have caused the diff outdrives to eat up just one side? Is this a shimming issue INTERNALLY or just age and wear/tear?

Just for reference there is no shim on the crown side but again all was meshed well...

View attachment 170037View attachment 170038View attachment 170039
@Edough13 @jondilly1974 @SrC

I put the HR aluminum dif cup in my 3s senton ran it on 6s with a 150 esc 0 issues except stupid fast so now just running 3s and lost track of how many packs ran through still strong runner and waiting for front HR cup and steel gear

 

[Camaroboy383]

@Camaroboy383 @SrC

Thx...seems the pic posted or not posted.... but I am lost if I screwed the top those how the pins could move....I agree this happened just now a loss of confidence now when I close the diff back up again, LOL

Yes the pic posted.... The pins that enter the shallow bores in the cap are the culprit, that 100% explains why that cap side of the diff failed..

When installing the cap you have to pay close attention.. it should seat against the edge of the cup easily.. If you have to squeeze it to get it to seat the pins are not in the shallow bores.. A little wiggling on the cap may be needed..

Another important thing to note.. and maybe this was the cause.. The cup side should be assembled first completely dry before adding any fluid... If you had any fluid in the deeper pin bores of the cup the pins will not seat with out some major manipulation due to hydraulics...

Fluid in those deep bores will hydraulic the pins back out after being pushed in, giving you an even greater chance of pin misalignment...

 

[parcou]

Yes the pic posted.... The pins that enter the shallow bores in the cap are the culprit, that 100% explains why that cap side of the diff failed..

When installing the cap you have to pay close attention.. it should seat against the edge of the cup easily.. If you have to squeeze it to get it to seat the pins are not in the shallow bores.. A little wiggling on the cap may be needed..

Another important thing to note.. and maybe this was the cause.. The cup side should be assembled first completely dry before adding any fluid... If you had any fluid in the deeper pin bores of the cup the pins will not seat with out some major manipulation due to hydraulics...

Fluid in those deep bores will hydraulic the pins back out after being pushed in, giving you an even greater chance of pin misalignment...

Sir...you hit it in the last statement! Thx

Last time I installed it back as I was not paying good enough attention when putting the top on. I had it turned the wrong way and pins were not going to the right slots....needed to turn it...but it did grab a pin or two. I did lift the pinnout and put it back in but I did have fluid in the cup...it went back in with a push but as I see now with fluid all in the bores pressure must have caused them to lift and move. Makes sense now....

Glad I keep a spare backup diff I got from Jenny's so I will put that one in tomorrow....

 

[Surchaufeur]

To me it looks like the pins go savegely spread apart to tear

 

[parcou]

I'm wondering if it's when you put it back together it wasn't all aligned right. I just did mine last night as I just went to the CNC crown gears and inputs which require a new cups also. Anyways I had one give me a lot of trouble I'd get it together and would spin like it was supposed to then all of a sudden would only spin about 180°. I had to take it apart and put it back together a few times before the pins and gears lined up right and it finally stopped doing it. So wondering if yours did the same and when you first checked was fine but then like mine would lock halfway after a few spins. Just very odd it would spin half way in either direction and then stop and lock up at one spot after spinning fine first few times. Just a possibility or just from age they finally gave or you had a rock get stuck between the driveshaft and A arm and the other side spun hard and snapped the gears on the side that couldn't spin?

I know your gear setup is different from my setup wondering how your shimming worked out?

I now have the Arrma CNC metal diff (crown/input) gears for the rear but the cup is plastic. It came with the plastic yoke but I already had the HR yoke. The Arrma full metal diff setup with plastic yoke comes with 2 shims on the crown side and one on the cup side. Way more than I would have stock or with the HR yoke and stock diff. HR yoke and stock diff only had one shim on the crown side only.

I placed Arrma CNC as is in the HR yoke so you have 2x shim on the crown side and the 1 shim on the cup side fully assembled. Spun just fine no binding at all but did not feel or sound like the metal 6S diff gears on my Infraction nor the videos I have seen with the 3S doing metal diffs via Arrma or HR. I removed all the shims from the metal yoke on the CNC diff with the HT yoke and then I had no binding. I had that feel and sound of the gears meshing closer but no binding. On that fully assembled diff this gave me also a slight tick, little free movement in the input gear. I went one step further and added only 1 shim on the crown side only. Fully assembled and that took away that little input tick & slight movement with no binding. Gear mesh is a little more pronounced in the sound/feel but no binding but like P&G they are together. At this point, I have no added any Red/tack

Wondering as I am trying to figure out the right mesh....how did you shim and your outcome? Each person has a different setup just curious.

Thx

Anyone else input is welcomed

 

[BulletRCs_NZ]

Wish I could help I just went with the plastic yokes on my CNC Steel diff and haven't had any issues. I've removed the diff a couple of times to service it and it's in perfect condition still.

TBH most of my diff issues have disappeared in my other rigs now I'm seating in my diff bearing correctly. I did issue an issue with my front Senton diff yesterday but that was a exploded diff bearing, the crown and input gear were still usable.

Sorry not much help but I like talking about diffs.

 

[Edough13]

I know your gear setup is different from my setup wondering how your shimming worked out?

I now have the Arrma CNC metal diff (crown/input) gears for the rear but the cup is plastic. It came with the plastic yoke but I already had the HR yoke. The Arrma full metal diff setup with plastic yoke comes with 2 shims on the crown side and one on the cup side. Way more than I would have stock or with the HR yoke and stock diff. HR yoke and stock diff only had one shim on the crown side only.

I placed Arrma CNC as is in the HR yoke so you have 2x shim on the crown side and the 1 shim on the cup side fully assembled. Spun just fine no binding at all but did not feel or sound like the metal 6S diff gears on my Infraction nor the videos I have seen with the 3S doing metal diffs via Arrma or HR. I removed all the shims from the metal yoke on the CNC diff with the HT yoke and then I had no binding. I had that feel and sound of the gears meshing closer but no binding. On that fully assembled diff this gave me also a slight tick, little free movement in the input gear. I went one step further and added only 1 shim on the crown side only. Fully assembled and that took away that little input tick & slight movement with no binding. Gear mesh is a little more pronounced in the sound/feel but no binding but like P&G they are together. At this point, I have no added any Red/tack

Wondering as I am trying to figure out the right mesh....how did you shim and your outcome? Each person has a different setup just curious.

Thx

Anyone else input is welcomed

I also just have the stock yokes for my new CNC gears. I only used the one shim opposite the ring gear and mesh was good nice and smooth I haven't ran them yet for a pack just tested in the garage but truck rolls and runs nice and smooth.

 

[parcou]

I also just have the stock yokes for my new CNC gears. I only used the one shim opposite the ring gear and mesh was good nice and smooth I haven't ran them yet for a pack just tested in the garage but truck rolls and runs nice and smooth.

Thx for the update... still good feedback! On your 3S BR or Granite what punch so you run at? Mine is 6 stock with 9 as max.

 

[Edough13]

MInes different as I run the 150A esc so think it's little over half like 5 maybe I don't remember lol.

 

[parcou]

@BulletRCs_NZ @Edough13

Thx post sharing about your metal diff. I still have more runs and testing to do but had a chance this evening to get 2 full 3S 6200mah runs. You know when you get something new try to feel it out and not get caught on the high of having something new.

I ran it in my same spot on loose dirt and in past I did not get the dragster takeoff wheelie (not a full walking wheelie) so it was nice to see the front end lift a little. Hate wheelies in general but the gearing felt really good in the rear. It had rained 24hrs prior so the dirt was not dusty or extremely loose but was not wet either, so I need to see what it will do when it is bone dry.

I look forward to more bashing to keep testing. My hope since I have strengthened the rear diff that this does not transfer that energy to my plastic spur as the next weak point. I'm hoping the M2C motor plate adds stability to that area for the spur.

Thx fellas