Big Rock Arrma 3s differential super tight after replacing the 2 big outside gears

[iLikeRCs]

So my diff is super tight (can barely spin it by hand) after my sun and pinion gear broke and I replaced them with new ones. There is this shim that i have no idea where it goes, maybe that's the issue?

Video here:

 

[Johnny b]

It does seem tight. A little grease smeared on the ring gear will help. I have two 3s rigs and they both had to wear in a little. Not sure if that's the case with yours though. Ensure you did not crank down the yoke halves to tight also.

 

[Moonstonemike]

Is the shim a larger one. Like the size of the bearings. You prob need to add it opposite the crown gear side to shift it over. Also check that the bearings on the pinion are fully seated (they are pretty tight) or else the pinion sits too far into the crown.

 

[iLikeRCs]

Is the shim a larger one. Like the size of the bearings. You prob need to add it opposite the crown gear side to shift it over. Also check that the bearings on the pinion are fully seated (they are pretty tight) or else the pinion sits too far into the crown.

That could be it, the bearings on the pinion were really freaking hard to get on there. There's still a little gap at the front one, but it just won't go on further. I even tried hammering it

 

[Moonstonemike]

That could be it, the bearings on the pinion were really freaking hard to get on there. There's still a little gap at the front one, but it just won't go on further. I even tried hammering it

There is a small step the size of the inner bearing race so it won't sit flush up against the back side of the pinion. On my last 3s car I filed that step down a bit until the mesh felt smooth. Try adding that shim in first and go from there.

 

[iLikeRCs]

There is a small step the size of the inner bearing race so it won't sit flush up against the back side of the pinion. On my last 3s car I filed that step down a bit until the mesh felt smooth. Try adding that shim in first and go from there.

I added the shim now, a little better but still way too tight. Guess I'll try filing down the pinion, only Issue is now I gotta get the bearings off of it

 

[Moonstonemike]

Yeah it's a pita. What I did is put it in a drill and filed the lip down and the shaft a bit so the bearings went off and on easier.

 

[iLikeRCs]

Yeah it's a pita. What I did is put it in a drill and filed the lip down and the shaft a bit so the bearings went off and on easier.

That's smart, thanks for the tip

 

[chilly81]

I just went through this very recently but wasn't as bad as yours. Don't expect them to be buttery smooth like a racing buggy, but that seems awful tight to me.

Make sure all the bearing seats are super super clean. Any debris in the bearing seat, when you put the new bearings in, will act light a tightening shim and screw things up. Take pick and make sure the corners are clean and everything.

People have mentioned the only other things I can think of looking at.