Sorry to post on as two year old thread as my first contribution. I found the threads as I have the same issue, won't tilt up or down, stripped out the housing and then found a small bushing under an allen Key stopper, mine has worn pretty well away.
Come online expecting to see this is the common problem and confronted with more about motor and steering column replacement :(
Anyway the bush was available from the local Lexus dealer (by special order from Belgium) and has part number 47583-60010 Steering Stopper Number 1 it can be seen on this diagram, Part was £2.00 plus VAT so would be the first thing I decided to try. Part will be delivered next week will update if it sorts it.
If this is common knowledge and I have just not found it on my searches of the forum my apologies