https://www.ebay.com.au/itm/Magneti...d-e7fe-4b7a-81a5-9ac6012e88f9&redirect=mobile
You need one of these or an older mechanical type will do.... read up on the subject! It's far to much to write out and really, I shouldn't do It anyway!
YOU ARE PLAYING IN A SPECIALIST FIELD MY MAN, brakes, steering and diffs/tailshafts should never be worked on if you have little idea of what you are doing! Ever seen what happens when you drop a tail shaft or have your diff locked up at 80klms! Naaasty shite indeed...
Me personally, I'd change out ALL the Universal joints, check diff pinion angle whilst out, re fit and check tailshaft angels... if needed, fit leaf/diff shims to roll and adjust diff pinion angels...
Oh, also check for damage to the tail shafts, make sure there are no balance weights missing! And another thing, those bolts from tailshaft to diff pinion should be replaced also... You can only tension bolts down so many times! And im betting LIKE MOST, have been tensioner down over 2 times by now!
Think replacing 4 bolts is over kill! Think again! $10 $20 for peace of mind I say! And remeber, it's not just your family on the road eh...
All the best and make sure you keep on asking questions and research research research... remeber, drive trains,steering and brakes are a specialist field for a reason!
Never stop asking questions here and with mechanics you can talk with in person, this is not a measure twice cut once trade- you measure 3 times and again in these fields
Be safe....