Changed Gen 2 front wheel bearing, cleaned up splines on driveshaft, tightened bolt correctly (45 Nm then 80 degrees)
Afterwards, a few days, noticed slight clonk on changing drive from forward to reverse.
Had this before so checked and bolt was loose so tightened it correctly again (this worked last time)
However the clonk is reduced but still present - I don't like it.

My difficulty is that I think it is a stretch bolt (no strength marking, 13mm head, 10mm threaded section) so I'm worried about tightening it again.
I want to take it out, clean up the splines by moving driveshaft in and out of bearing, once clean, add Loctite to fill up the gaps as far as possible, then tighten up to same torque as it took to remove it or the 80 degrees whichever is closest.
Will it stand another tightening, anyone had this?
Comments?
 

In my experience using Loctite on a stretch bolt that has been reused is a waste of time because it will loosen again even with the Loctite on it.

If this is a stretch bolt (and I don't know) then you need a new one.

For future reference:
Unsure if it is actually a stretch bolt (torque to yield) as it does have a 2 stage tightening regime but has no strength marking and is threaded all the way along i.e. doesn't have a waisted section that will stretch and there is variable advice on this:
https://en.wikipedia.org/wiki/Torque-to-yield_fastener

Random Internet information:
https://www.underhoodservice.com/gm-torque-yield-tty-fastener-use-reuse/

But the item is here:
https://www.ebay.co.uk/itm/393525343220
This one is marked 8.8 when I'd expect a 12.9 if it was TTY.
ETIS for driveshaft doesn't actually say "Always use new bolt" for work on driveshafts.
I'll just get one.

Thanks!

I've seen these both snap and loosen over time.  I would not be re-using one at all.

To complete this, I bought a new bolt:
https://www.ebay.co.uk/itm/393525343220
Removed wheel and old bolt, cleaned splines with brake cleaner and was able to move driveshaft in and out by about 2 cm to access inner and outer area.
Then added Loctite with a syringe to both inner and outer area of the driveshaft and again moved it to spread along the splines.
Fitted new bolt (extra Loctite) 45 Nm then 80 degrees.
Leave for 24 hrs to attain full strength.
Looks like it's fixed, no more clonk!