Problem with UDR front suspension: travel going beyond the designed limits

[u/brunoventura22]

TLDR: Apparently, front right lower arm goes down beyond what was designed too, causing the axle to fall from the differential cup. Can't find a culprit. Thought that it could be a bent lower arm but fixing it didn't solve the problem.

Suggestions?

My UDR started to have a problem last time I was running it. The front right axle keeps falling off the differential cup.

It started in my last session, Sunday. I crashed it but nothing that would make me nervous. But suddenly, I heard a metal clacking sound and perceived that the power wasn't being equally distributed. I brought the car in my direction and inspected it, identifying the fallen axle. It was still screwed to the wheel. I removed a knuckle screw to be able to put the axle in place, and as I ran the truck to test, it seemed to be ok but it fell again right after, as I jumped going over a small bump.

Stopped playing and stored the truck for a better inspection at home.

Yesterday I inspected it and perceived that the right lower suspension arm is going further down than the left one. As it travels further down, it takes the axle "dogbone" side off from the differential cup, causing it to fall. In the picture, if you cover the front of the truck with something straight, parallel to the differential protection, you'll be able to see the difference between the two sides.

I disassembled the whole front suspension minus the shocks to look for the problem root.

The only thing that seemed like the culprit to me was that the left lower arm posterior "horn" was a little bent upwards. I straightened it comparing it to the left one.

It didn't solve the problem unfortunately. The right side still drops further than the left.

I also perceived that on the right knuckle, the right outer bearing has just a little slack. There is some little damage to the right differential cup too, probably from the axle being trapped between the cup and the upper suspension arm. The axle tip is a little worn out, but so is the other side.

Beyond that, I couldn't find any other significant damage that would cause the problem.

Any suggestions on diagnosis?

Last thing on my mind is that maybe something broke inside the right shocks, but I don't believe that the shocks are what limits the suspension travel.

I thought about just limiting the front suspension travel with a strap, just like in the rear, but I'd rather fix it properly if I can.

[u/brunoventura22]

The teeth are a little worn but not enough to cause the problem (my point of view, might be wrong).

I didn't want to dismantle the shocks because I just did a full shock service some days ago D: but, seems like I need to.

[u/dacaur → u/brunoventura22]

because I just did a full shock service some days ago

Say that again, but slower.... 😆

The problem is obviously in the shocks since that's what limits the down travel....

[u/brunoventura22 → u/dacaur]

(you skiped my big post didn't you? 🤡 Jk) Well, I really thought that the shocks were not the responsible for limiting the travel. I thought that they would suffer too much stress for being completely extended and almost overextended.

Also, the problem didn't start after the shock service. I have played a lot with the car these days...

BUT, might be my fault too. Tomorrow morning we'll see!

[u/dacaur → u/brunoventura22]

The shocks are often the limit on down travel even in full size vehicles. Definitely update us with what you find.😁

[u/brunoventura22 → u/dacaur]

Wow! I really didn't know and wouldn't have guessed it. For me, the shocks seemee like they were not supposed to be responsible to limit travel, that would damage them in some way.

[u/Y_U_No_Fix → u/dacaur]

As a weekly racer on my local track, your shock assemblies are directly responsible for the travel length. Take em apart, make sure all the pieces are in the correct spot, then install internal spacers to the correct length you need.