GMC 1989 Light Duty Truck, Repair Manual, Page: 10 / 998

OA-4 GENERAL INFORMATION
products are d esig ned to new, international stand ards that
m ay not yet be m anu factured by som e non-dom estic bolt
a n d n u t s u p p lie r s . In g e n e r a l, e x c e p t fo r s p e c ia l
applications, the com m on sizes and pitches are:
M 6.0 x 1 M 10 x 1.5
M 8 x 1.25 M 1 2 x 1 . 7 5
SIX LOBED SOCKET
HEAD FASTENERS
Six lobed socket head (Torx) fasten ers are used in som e
applications on vehicles covered in this m anual (figure
15). T h e door striker bolt is of this design.
PREVAILING TORQUE FASTENERS
A p revailin g to rq ue nut is d e s ig n e d to d eve lo p an
interferen ce b etw een th e nut and bolt threads. T his is
most often acco m p lished by distortion of th e top of an
all-m etal nut by using a nylon patch on th e th reads in the
m iddle of th e hex flat. A nylon insert m ay also be used as
a m ethod of interferen ce b etw een nut and bolt th reads
(figure 16).
A prevailing torque bolt is d esig n e d to develop an
interferen ce b etw een bolt and nut th reads, or th e th reads
of a tap p ed hole. T his is acco m p lished by distorting som e
of the th rea d s or by using a nylon patch or ad h esive
(figure 16).
RECOMMENDATIONS FOR REUSE:
1. C le a n , unrusted prevailing to rq ue nuts and bolts
m ay be reused as follows:
a. C le a n dirt and other foreign m aterial off the
nut or bolt.
b. Inspect the nut or bolt to insure th ere are no
cracks, elo ng atio n, or other signs of ab u se of
overtightening. (If th ere is an y doubt, replace
with a new prevailing torque fa s te n e r or eq u al
or g rea ter strength.)
c. A sse m b le the parts and hand start th e nut or
bolt.
d. O b s e r v e t h a t , b e f o r e f a s t e n e r s e a t s , it
develop s torque per th e ch art in figure 13 (if
th e r e is a n y d o u b t, r e p la c e w ith a n ew
prevailing torque fas ten er of eq u al or g rea ter
strength).
e. T ig h ten th e fas ten er to th e torque specified in
th e ap p ro priate section of this m anu al.
2. Bolts and nuts which are rusty or d a m a g e d should
be replaced with new parts or eq u al or g rea ter
strength.
Tools d e s ig n e d fo r th e s e fa s te n e r s a re a v a ila b le
com m ercially. However, in som e cases, if the correct tool
is not available, a hex socket head w rench m ay be used.