Big Rock Rear End Noise

[Cdnguy]

Just got back into the hobby and purchased a Big Rock and a lot has changed since my old Blackfoot.

I find it rather disappointing that on the third battery pack I am getting a grinding noise from the truck. Pulled the driveshaft, and it's still there. I'm figuring that something is piling up in the rear differential.

Couple of questions that I hope to get answered.
1. If the ring gear is eating itself up can just the ring and pinion be replaced, and would the " warranty" cover the cost of parts?
2. Would it be worth it to go to a steel set of gears instead?
3. Any other ideas what would be causing this noise?

 

[SrC]

Steel is better obviously. And Quite costly at that! And they still wear out anyway. $$, Considering the whole price point of your 4x4. You will see.
If your BR 4x4 is that new, Call HH, they should warranty it for you, with a valid receipt. For 2 years. Could have been sloppy diff assembly, poor shimming....Ask HH for the Ring and Pinion set. Both.
Using JennysRC.com for parts is one great option. Keep that in mind down the road.
Obviously open up the diffs to confirm first.
Start wrenching.
Go over both front and rear diffs. I bet the diff oils are low also. Have the oils on hand. You always need oils on hand anyway. Part of the hobby.. These are not truy RTR's as you can see. They should not crap out like this on its 3rd pack. But its a thing. Just poor Factory QC. You are not alone. And won't be the first or last.
Make sure to Grease the ring and pinion gears with any Automotive Grade Grease. A Synthetic type even better. (Mobil 1 or Superlube) I use both of these.
I also use Lucas Marine Blue grease with my Crawlers, because I run them in streams, water and snow. (Extremely water resistant properties.) Depending on the rig in hand. I don't run any of my fast bashers in or near water.

Welcome to AF.

 

[Doom!]

I'm sorry but you can't just give your thread a title like this, we are a bunch of grown up sized children!

 

[SrC]

Yeah sometimes that rear end makes a slap slap noise.

 

[MrTitanium]

Just got back into the hobby and purchased a Big Rock and a lot has changed since my old Blackfoot.

I find it rather disappointing that on the third battery pack I am getting a grinding noise from the truck. Pulled the driveshaft, and it's still there. I'm figuring that something is piling up in the rear differential.

Couple of questions that I hope to get answered.
1. If the ring gear is eating itself up can just the ring and pinion be replaced, and would the " warranty" cover the cost of parts?
2. Would it be worth it to go to a steel set of gears instead?
3. Any other ideas what would be causing this noise?

Another Canadian??? Dang! Pulling your leg. Welcome aboard.

Are you sure it’s coming from the diff(s)? Could be debris between the motor pinion and spur gear. Check that before going to the diffs.

I’ve owned 3s Arrmas. Although the diff gears are plastic, they hold up quite nicely. Mind you, I never ran them out of the box as I strip down my rides before I run them. Some TLC is required… and highly recommended.

There’s a strong chance that you stripped tooth, and/or, bearing(s) shot out and cause a misalignment between the pinion and crown gear.

Take apart one diff at a time. Clean/wash all internal components and inspect. There’s also a chance that those little planetary gears stripped out. Those are cheap cast aluminum and have a bad rap of spitting out teeth.

Last step should be doing a dry assembly. Do not add grease/oil. Install all the parts as you normally would and see how the backlash is. Any high spots as you rotate the gears? Yes? Inspect where and why.

Need shims? Buy accordingly.

Do not switch to metal (spiral) diff gears until you find the issue as they are very expensive. Plus, spiral gears are more sensitive to adjusting.

Lucas Red & Tacky is all I use in the diffs. Tried many other lubes, but she works best IMO.

Hope this helps.

 

[Cdnguy]

Thanks for the advice, I'll probably take the rear end apart this evening and see what condition it's in.

What types of chemicals would you say is needed for routine maintenance and rebuilds? Already have red and tacky, any others considered to be necessary?

 

[MrTitanium]

Thanks for the advice, I'll probably take the rear end apart this evening and see what condition it's in.

What types of chemicals would you say is needed for routine maintenance and rebuilds? Already have red and tacky, any others considered to be necessary?

If you don't have an ultra sonic cleaner, soaking all components in acetone overnight gets them clean. Might want to get in there with some q-tips and an old (don't use your wife/girlfriend's) toothbrush afterwards.

 

[parcou]

Thanks for the advice, I'll probably take the rear end apart this evening and see what condition it's in.

What types of chemicals would you say is needed for routine maintenance and rebuilds? Already have red and tacky, any others considered to be necessary?

Great advice above, and the stock diffs can last with some pre TLC and some TLC between runs.

After doing the above to check the diff, gears, and bearings, nothing is binding... On my 3S after runs

Each runs or after 2x runs depending on the conditions you run it in:
Check the bearings, listen, and if you find a loud crunchy noise from the hubs wheel hubs, clean the bearings and or replace

Even with well lubed wheel bearings, I still like to stay SC1 around the suspension area to help as added protection.

On all 3S models, the power module can collect a lot of trash between it and the rear diff. This bearing can and will lock faster than others, so I clean and change it often. I did cut a hole in the chassis to help, and some put tape over the power module gear.

I will say all this is no help if they do not check the diff, gear mesh.

 

[RCbuzz]

Welcome aboard!

To echo what others are saying, start tearing into the truck to see what's going on. One great thing about the 3S line (and others) is how easy it is to work on.

Once you have narrowed down the problem you can go from there. Horizon support is great (especially for new customers). If you feel the problem was a defect I wouldn't hesitate to reach out to them.

You can also check this out (sealing the 3S power module). I do it to every 3S RC we have. Most of my plastic spurs still look great after several packs. https://www.arrmaforum.com/threads/help-me-upgrade-my-senton-3s-for-sand.20322/post-297587

Keep in mind that the diffs and chassis are all plastic. Best bet is to use a plastic safe grease. Some greases WILL soften the plastic causing it to fail shortly after. We have seen some brands of white lithium grease turn the gears to mush. Oddly, Red and Tacky has never seemed to mess with the plastic.

Some of the best grease I have found is Super Lube Silicone Grease. (https://www.amazon.com/Super-Lube-92016-Silicone-Translucent/dp/B0081JE1PM)

This stuff is great too, it does not stick as long but I have found it works nicely for packing bearings. (https://www.amazon.com/Super-Lube-41160-Synthetic-Translucent/dp/B0083R1FME)

Oh, buy yourself a quality set of Hex Drivers too . MIP makes a good set but know that their 2mm hex is too short for the differential inside axles .

 

[SrC]

Thanks for the advice, I'll probably take the rear end apart this evening and see what condition it's in.

What types of chemicals would you say is needed for routine maintenance and rebuilds? Already have red and tacky, any others considered to be necessary?

I use automotive Brake cleaner spray . Fairly cheap, cleans silicone oil and grease well quickly, then evaporates. I place parts in a container and spray them down. An old tooth brush helps greatly. Then lay out all the cleaned parts on a clean surface or paper towels to work/ rebuild. A parts try or similar to organize them, works out great.
Look over the cleaned parts well for any broken/worn ones.
You can't rush building diffs. After a while, you will do them blindfolded. It's all just muscle memory.
Well built and "filled diffs" will last quite a while when shimmed properly. Your mileage will vary based on how hard you drive. I think 15-20 runs is about average, per the manual between maintenance intervals.
If shimming is needed, always be prepared with shims on hand.

 

[Cdnguy]

All great help and advice, I pulled out the diff last night and both the pinion and spur gears where fine.
I also opened up the rear end and both the crown and rings gears were okay as well, added grease and hopefully I can take it out tomorrow for a rip to see if the problem has been resolved. If not then I'm assuming that the diff is pooched.

 

[RCbuzz]

Feel free to post up a video, a lot of us have 3s rigs (including myself) maybe we can help identify it.

Also check the rear hexes, sometimes they strip.

 

[Cdnguy]

Update, I believe that mysterious noise has been resolved. I took rear apart no broken teeth fortunately , added red & tacky reassembled everything.

Just took it for a quick rip and no more noise.