Big Rock Diff rebuild

[Cjones85]

I’m getting ready to do a full bearing replacement and since I’ll have the truck tore down and diffs out I would like to replace the fluid/grease that came in them stock. Any recommendations on fluid weight and such? Thanks in advance

 

[jondilly1974]

10k sct is stock. Some people like 30k up front to reduce ballooning. The truck will understeer if you go too heavy up front. If you race on a track, which I doubt you do with a BRCC, you would want light fluid, like 5k or 7k to get more diff action.

 

[Cjones85]

10k sct is stock. Some people like 30k up front to reduce ballooning. The truck will understeer if you go too heavy up front. If you race on a track, which I doubt you do with a BRCC, you would want light fluid, like 5k or 7k to get more diff action.

I do some racing with some friends on a track I made in my backyard which usually ends in bashing lol but I like a good balance. I don’t mind the ballooning with the stock fluid so maybe I’ll go back with that

 

[jondilly1974]

I do some racing with some friends on a track I made in my backyard which usually ends in bashing lol but I like a good balance. I don’t mind the ballooning with the stock fluid so maybe I’ll go back with that

Yeah anything heavier and it’s gonna push in corners like it’s on skids. If you want the tires to bite in the corner, keep it 10k. Another trick is toe out in the front helps corner better too.

 

[AimlessRC]

Having just gone back to 15k front, 10k rear from 30k front 15k rear I attest that heavier isn't always better.

I like my truck to turn on the gas, even for a basher. I wouldn't exceed 20k in the front, or 15k in the rear. As jondilly said, toe-out and a bit of negative camber can help reel the steering in a bit more, but keeping the rear-end light is key. I notice hardly any ballooning unless I'm in the air with 15k in either end, but then again my tires are vented and wheels are plugged.

 

[Lazy Bushman]

Depends on the type of terrain you run and if you race. I run 100k front and rear and 500k centre and hasn't let me down.

 

[Outcastblxnut]

60 100 30 here and I love it

 

[Mathieu]

There is a good video on 3s/4s diff rebuild I though I would post a link here: ARRMA HOW-TO: 3S AND 4S DIFF REBUILD | GEARS, BEARING, GREASE AND DIFF FLUID.
I thought I would post it here for others. Let me know if its okay.

I have a question at 4:31, what is the tool he uses (a flat screw driver that is bended).
Sorry I just got a Vorteks for my son, I back in RC myself (but new to surface), and I trying to catchup on the tools.
I need to do a first maintenance (one battery so far) from factory to top the fluids and adjust the mesh (I sound like I know what I am doing but it is not the case, I have been reading this awesome forum and watching youtube video).

Thanks everyone for your contribution to this forum. It is very valuable for newbie like me.

 

[Velodromed]

There is a good video on 3s/4s diff rebuild I though I would post a link here: ARRMA HOW-TO: 3S AND 4S DIFF REBUILD | GEARS, BEARING, GREASE AND DIFF FLUID.
I thought I would post it here for others. Let me know if its okay.

I have a question at 4:31, what is the tool he uses (a flat screw driver that is bended).
Sorry I just got a Vorteks for my son, I back in RC myself (but new to surface), and I trying to catchup on the tools.
I need to do a first maintenance (one battery so far) from factory to top the fluids and adjust the mesh (I sound like I know what I am doing but it is not the case, I have been reading this awesome forum and watching youtube video).

Thanks everyone for your contribution to this forum. It is very valuable for newbie like me.

That is probably a small prybar. I can’t watch the video right now but I’m sure he’s using it to remove the bearings off the differential, right? Same thing can be accomplished with a medium size flat head screwdriver. Sliding it under the bearing and then twisting it gently all the way around until it pops off.

Basically, you need a decent set of hex drivers. Ideally ones that are long enough to reach up the driveshaft to unscrew the retaining screw. I’ve been using this set for over a year and they are solid as well as affordable. You will hear about MIPs a lot but unfortunately they’re 2 mm is too short to fit up the driveshaft. They are also extremely expensive and due to the hardened nature of the steel, a bit brittle. I have broken one simply by dropping it accidentally.

You also need differential fluid. Stock is 10k cst. I have found that 15 to 20K in the rear and 25 to 30K upfront works better. Also, you’ll want to top off the shocks. Shock fluid goes by weight, stock is, I believe, 45 to 50wt and works good enough. Make sure you don’t get CST and weight mixed up because they’re drastically different. There’s many different brands and I just tend to get whatever is the best price. Typically they come in 2 ounce and 4 ounce bottles, I try to find the 4 ounce bottles as it’s usually a better deal. Watch a YouTube video on disassembling and bleeding the shocks. It’ll save you some grief.

Get a pack of bearings as well. Stock bearings are not great and typically will not last long. Jim’s, Fast Eddie, TBR, Avid among others will work. I put an example below.

The spur/pinion mesh can be difficult and frustrating at first. But once you get the feel and understand the sound that a good mesh makes, it’ll be simple. There are any ways of doing it as you’ll find on YouTube.

Be extremely careful when adjusting a slipper in the beginning. If you tighten it just a little bit too much It’ll strip the threads or pop the brass ring inside, then you’ll need a new hub assembly. I tend to tighten it until I feel the least bit of resistance, then tighten a little more and test it out in the car. It’s easy to adjust while in the car by removing the driveshaft and sliding a 2mm up the spur hub. I will tighten a little bit at a time until it’s just right. I go by sound. If the slipper screams, it’s too loose. If it makes no sound before engaging, it’s too tight. If it chirps a little bit then engages, it’s about right. I tend to keep the slipper a little bit loose as it’s easier on the drive shafts and differentials. Slipper pads are cheaper than driveshafts and differentials after all.

When you pull out the differentials and remove the bearing you should find a shim underneath the bearing that is opposite the ring gear (big gear on the differential itself, the small gear is the input gear). Make sure to put that back on when you reassemble. After 10 to 15 packs you may need to remove that shim in order to keep the mesh between the ring gear and input gear tight. After another 15 packs or so you may have to add that shim to the ring gear side of the diff. So don’t lose it lol.

Below is a link to the exploded view for the vorteks. This can be extremely useful when trying to figure out names of parts, and how they are assembled. They have them for all the armored cars on their main website. Arrma-rc.com.

Lastly, you responded to a 3+ year old post. It’s not a big deal, but some people will hack on you about it. So look at the dates when you respond to posts. If you want to revive an old post, I’ve found it useful to simply say something like ‘I am revising this old post’, at the beginning. It keeps the hecklers at bay. Good luck, man and enjoy the Hobby!

https://www.arrma-rc.com/on/demandw...284/Manuals/ARA4305V3-Exploded View-MULTI.pdf

Neewer - Set of 4 Hexagonal Screwdrivers Made of Titanium Nitride with Coloured Handles.Compatible with 1.5, 2, 2.5 and 3mm Screws. https://a.co/d/hwB7gFE

TRB RC Arrma Granite Senton Big Rock 3s BLX Bearing Kit (27) https://a.co/d/9PFHFL5

 

[Mathieu]

Thank you so much Velodrome for your tips and advices and for taking the time to reply.

I will take a look at the links!

Thanks again you also covered some other questions I had!

I apologize for reviving this old post.

 

[Velodromed]

Thank you so much Velodrome for your tips and advices and for taking the time to reply.

I will take a look at the links!

Thanks again you also covered some other questions I had!

I apologize for reviving this old post.

You are welcome and all good. Old posts are good for research purposes. If you have any other questions just post about it underneath your cars category. More people will see it that way. I only saw this by accident. If you want to call someone to attention to your post, put the @ in front of their name…@Velodromed