I have got rid of the squeaks on my GT.
The upper bushes were quite easy to change and I did take advice from here and used powerflex bushes and followed a step bt step guide with photos (sorry don't have the link). Taking the old bushes out was hard going and I needed a large vice and brute force. I therefore think that as they were so tight that it would not be possible to get grease in there with a grease nipple, there is no void for this inside the arm.
I would recommend the Powerflex and they are still quiet after 12 months.
Billy, thank you.
Which bushes were hard to remove; the steel insert or the rubber?
I am not sure how the top swivel is supposed to work and haven't yet stripped one apart but I have seen the assembly pictures so what you have said raises a question:-
Are the steel bushes supposed to remain still in the rubber or powerflex bush and the pivot action take place between the steel bush and long bolt?
I suspect that the swivel action is supposed to be between the two steel components and when cleaned up (rust and crud removed) there will be a suitable clearance for grease to be forced into.
If that is what is supposed to happen I suspect that the steel bolt starts to seize in the steel bush forcing the pivot action to take place between the steel bush and rubber thus generating the squeak noise.
My guess is where powerflex bushes are fitted even when the pin seizes to the steel bush and the steel then turns in the poly bush it doesn't squeak because they are poly and not rubber - possible? Without having had one apart I may be missing all this by a mile.
So, is my solution possible but now needing the drilling to go through the rubber and steel insert thus lubricating the steel bush to steel pin interface?
Looks like I need to get my sons squeaking suspension apart and have a good look for myself. Do I need to fully remove the top wishbone to separate the bushes and lubricate the necessary components?