The various driveshaft bolts were listed by Triumph as special
numbers, not standard hardware (p/n 132023 for driveshaft, 144961
for propshaft). There is no dimensional difference between these
bolts.
I chose to replace them with high strength aircraft bolts and heat
resistant nylocs. The bolts are dead ringers for an AN6-7A bolt,
3/8-24 thread, 5/16 grip, 61/64 length under the head.
The only visible difference is the marking on the head; the 132023
has none, just a large circular depression, while the 144961 is
marked "ARB S". Perhaps someone in the UK is familiar with that
marking, but I can't find it listed anywhere.
I was never completely comfortable with the stock bolts - even
though they are a "special part number", they appear to be grade 5
and have a threaded portion bearing on the flange. In addition, the
standard nyloc nuts tend to come loose with time, something I
attribute to the relatively high heat in this area from the exhaust
system. The 5/16 grip of the stock bolt leaves one or two threads
inside the flanges - this is probably the highest stress area on
the bolt, and seemed like a bad idea. I replaced them with the next
size up, AN6-10A, which has a 7/16" grip. Running clearance is fine,
though installation is a bit fiddly. This leaves a small amount of
unthreaded shank showing, so it takes a single AN960-616 washer
under the AN365-624A nyloc nut. I considered using the thin AN960-616L
washer and the half-height AN364-624A nut, but the nut is rated for
shear loads only. Even though the torque is transmitted in shear,
there's a fair bit of clamping going on as well.
Since changing to the AN365 nuts, I have never found the driveshaft
nylocs loose when checking them - they used to *always* be loose
before.
You can get these parts at Coast Fabrication or Aircraft Spruce.
Contact information in the Monster List: www.dimebank.com/monster
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