Big Rock EXB Diff Help

[trexdd]

After my last outing with the truck, I made a boo-boo so now I’m fixing it and hopefully “upgrading” at the same time. I like the metal housings, that both ends are removable, easier to remove the crown gear and pin etc.

I’m hoping someone can help me with setting my mesh for the internal gears. Here’s a video I took hopefully it helps give a clearer picture

 

[ShankAaron]

Nice. Forgive the ignorance, but do they make a 3s/4s version? I can hear the BRCC and Senton yelling for a set from the garage......

 

[Sandracer_NL]

Sounds good, but it looks like at one certain point there is more sound and resistance. If so have another look at the internal gears if they are all smooth and undamaged. You could also put a small amount of diff oil on the gears or in the diff and check again for any the small amount of resistance is the same throughout a full turn.
Normally you should only shim on the ring gear side to get the correct mesh with the input gear and have no lateral play of the diff inside the diff housing.

 

[MrTitanium]

Nice. Forgive the ignorance, but do they make a 3s/4s version? I can hear the BRCC and Senton yelling for a set from the garage......

Yes. HR makes an alloy diff cup for both the 3s and 4s. Same part number.

@trexdd

When you say the internals, you’re referring to the four sun gears, right? The ARA311061 29mm units include instructions that dictate that shims are required behind each gear to prevent wear inside the aluminum case. Refer to illustration below.

I installed quite a few of these in my trucks and they all vary when it comes to shimming. There is a sweet-spot when doing a dry assembly. The trick is knowing how to find it.

 

[trexdd]

@MrTitanium yes, shims are in place according to that diagram you provided. Strange that the EXB one doesn’t have a diagram…

On a dry assembly, I can “feel” the detente caused by the gears. If I shouldn’t be able to “feel” them when rotating against one another on a dry assembly I will need to remove a shim. But no damage and no binding are present. I may just run it and if it breaks, it breaks and I learn

 

[MrTitanium]

@MrTitanium yes, shims are in place according to that diagram you provided. Strange that the EXB one doesn’t have a diagram…

On a dry assembly, I can “feel” the detente caused by the gears. If I shouldn’t be able to “feel” them when rotating against one another on a dry assembly I will need to remove a shim. But no damage and no binding are present. I may just run it and if it breaks, it breaks and I learn

As I wrote earlier, a steel shim is required behind each gear or gear will eventually wear into the case. Mugen sells shims for this too. I posted info about this a while back… maybe do a search on this forum.

 

[Shadows]

Make sure you have the gaskets in place. That little bit of space they create makes a difference in the gear lash inside the cups. Other than that, I'd have to see what you got going on in there.