Advice on how to tighten the Nyloc nut on a new, standard, Front strut insert please

[Rod1883]

Looking for advice again....

I've recently had new insert fitted in the nearside front strut.
At the top where the threaded part of the insert piston is visible by removing the large rubber grommet/cover on the top of the suspension tower - I'm struggling to get the large nyloc nut (24mm socket or AF spanner) tightened sufficiently to stop the washer below the nut being free to move. The threaded part of the insert piston that 'pokes up' through onto which that nyloc nut fits has a short non threaded section that has flat sides - 11mm across.

I've tried to hold that end still with an 11mm spanner whilst using a box spanner or ring spanner to try to tighten the nyloc. I can't get this to work though.

Has anyone any thoughts on how to get this nyloc tightened without the piston just turning. Is there a tool that can hold the piston still whilst tightening that Nyloc?

Thanks in anticipation

[sujitroy]

I've only managed to do it with an impact wrench. I installed Spax recently and the instructions say don't use an impact wrench. but I had to. I'm sure there is a special tool for this type of job.
Sujit

[jbuckl]

Offset ring spanner. Use a 7/16” open end to hold the piston.
otherwise, clamp the piston rod using rag & a large pair of grips on a portion of the damper piston that isn’t functional with the damper seal.
otherwise drill the piston per original for a castellated nut & split pin.

[mole42]

It can also help if the Nyloc is warm, not hot but not garage cold…..