My first Onslaught's legs didn't really hold together very well (the gray changes wouldn't stay put). I got another to see if it was a design or QC issue. Surprise, surprise, it's a bit of a QC issue. Between the two Onslaughts, I was able to put together one solid one. However, during the surgery, I noticed something pretty neat...

Firstly, I'm finding a lot of the recent leg ratcheting to be a bit annoying. Because thighs and knees can only move specific distances and not in between, finding a delicate pose can prove to be tricky. Some recent offenders include:

Universe Powerglide
Universe Silverbolt
Leader Megatron
Leader Bulkhead

So, back to Onslaught, while swapping his leg, I found by flipping a ratcheted washer over, I was able to get rid of the knee ratcheting, but still maintain a very tight joint making posing much easier.

Remove these two screws first:



You'll see the exposed ratchet-washer, gear side up:



Flip it over:



Put him back together and that's it!

I'm going to have a peak into some of the other figures I mentioned to see if it's as accessible.