BLX Diff - Not Seated in Yoke Correctly?

[ridgehead44]

Hey all,

I've been working on a BRRC slider that I'm piecing together. I oiled and assembled the rear diff this afternoon. I noticed there's only one way it will sit in the differential yoke. I put it in correctly, because the gears wouldn't move at all with the yoke on backwards. However, it still seems a bit tight/possibly not seated well? When I reassembled the back of the vehicle, I noticed that when I turn the rear drive shafts, the input gear does not turn. Is this normal, or is something wonky? I have 10K oil in the diff. Any help is much appreciated. Thank you!

 

[RCbuzz]

Grab the other axle and turn them in the same direction together. Does it turn okay?

If very tight or binding you need to check that one, the plastic yokes are seated all the way on to the bearings (tight fit) and two, you may need to add a shim to the diff on the non ring gear side.

Stock these are a little tight for my liking but I noticed after a couple runs they smooth out . I mean they are plastic.

 

[MrTitanium]

Normal, yes. You are not running a locker or ultra-heavy diff fluid.

 

[ridgehead44]

Grab the other axle and turn them in the same direction together. Does it turn okay?

Nope. Something is definitely binding. I'll take another shot at it tomorrow. If I can't figure it out, I'll take pictures of the yoke and share them to see if I'm missing something.

I did notice it was really difficult to fully screw the diff case together. I had just enough to cover that center bearing, which seems to be correct, based off the videos I saw on Youtube. Is it possible I have too much fluid in there? Could that cause an issue, or is it more likely the diff yoke?

 

[MrTitanium]

Nope. Something is definitely binding. I'll take another shot at it tomorrow. If I can't figure it out, I'll take pictures of the yoke and share them to see if I'm missing something.

I did notice it was really difficult to fully screw the diff case together. I had just enough to cover that center bearing, which seems to be correct, based off the videos I saw on Youtube. Is it possible I have too much fluid in there? Could that cause an issue, or is it more likely the diff yoke?

Yes. It’s possible to have too much oil. Shouldn’t be filled more than 80% and the other 20-ish percent will be occupied by the outdrive gear.

 

[Exc3l]

You tightened the 2 screws on the yolkes way too much!

Loosen up the screws even till you feel the the input getting easier and easier to spin. You need to set the mesh correctly.

You cant have too much oil, specially with 10k. If you do, when you are peicing the diffs together the rest of the oil will fall out.

 

[RCbuzz]

Nope. Something is definitely binding. I'll take another shot at it tomorrow. If I can't figure it out, I'll take pictures of the yoke and share them to see if I'm missing something.

I did notice it was really difficult to fully screw the diff case together. I had just enough to cover that center bearing, which seems to be correct, based off the videos I saw on Youtube. Is it possible I have too much fluid in there? Could that cause an issue, or is it more likely the diff yoke?

Something is up then, on all my 3S rigs I have both yoke screws fully tight, I do not leave them loose. That is what shims should take care of.

In this case, diff oil will have nothing to do with the binding you are experiencing because when grabbing both axles and moving it in the same direction there is no diff "action" so to speak, the entire diff should be spinning together.

In your video when turning the one axle and the other is spinning in reverse that is causing the internal diff gears to move through your diff oil. That is the action I am talking about .

Feel free to post up a couple pics of your diff when you get it pulled out and like I mentioned make sure the side of the yoke are seated all the way into the bearings. You likely need a couple shims though.

 

[ridgehead44]

I pulled out the yoke and looked at it. Here is what happens when I try to move the gears with the yoke fully tightened:

As you can see and hear, there's a bit of binding.

If I back the screws out about a half turn, they move much more smoothly, but it leaves a tiny gap between the two halves of the yoke, and it doesn't seem quite right. Suggestions? Shim, or something else? Thanks again in advance.

 

[RCbuzz]

Yep time to test with shims.

Thread 'Arrma 3S and 4S diff shims' https://www.arrmaforum.com/threads/arrma-3s-and-4s-diff-shims.23870/

Check out this thread

You will see these diffs can be all over the place and due to plastic wear, if you check them after a few packs they will likely need the shims adjusted.

 

[ridgehead44]

Hmmm, well the input gear and the diff case are both brand new, never been run before. Should I just get a new yoke? It's a $4.00 part. Or is there a way to shim the diff to create more space inside the yoke?

 

[MrTitanium]

I’m willing to wager that it’s an assembly issue.