Fasteners. Chevrolet Chevy P12 Chassis 1998

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1998 🢒 Chevy P12 Chassis 🢒 General Information 🢒 General Information 🢒 Fasteners

Table 1:	Prevailing Torque Specifications (Metric-Size Fasteners)
Table 2:	Prevailing Torque Specifications (English-Size Fasteners)

Metric Fasteners

This vehicle is dimensioned in the metric system. Most metric fasteners are very close in diameter to well known fasteners in the English (inch) system. Replace fasteners with those of the same nominal diameter, thread pitch, and strength.

A number marking identifies the OE metric fasteners (except cross-recess head screws). The number also indicates the strength of the fastener material. A Posidriv® or Type 1A cross-recess identifies a metric cross-recess screw. For best results, use a Type 1A cross-recess screwdriver, or equivalent, in Posidriv® recess head screws.

GM Engineering Standards and North American Industries have adopted a portion of the ISO-defined standard metric fastener sizes. The purpose was to reduce the number of fastener sizes used while retaining the best thread qualities in each thread size. For example, the metric M6.0 X 1 screw, with nearly the same diameter and 25.4 threads per inch replaced the English 1/4-20 and 1/4-28 screws. The thread pitch is midway between the English coarse and fine thread pitches.

Fastener Strength Identification


(1)	English Bolt, Grade 2 (Strength Class)
(2)	English Bolt, Grade 5 (Strength Class)
(3)	English Bolt, Grade 7 (Strength Class)
(4)	English Bolt, Grade 8 (Strength Class)
(5)	Metric Nut, Strength Class 9
(6)	Metric Bolts, Strength Class Increases as Numbers Increase

The most commonly used metric fastener strength property classes are 9.8 and 10.9. The class identification is embossed on the head of each bolt. The English (inch) strength classes range from grade 2 to grade 8. Radial lines are embossed on the head of each bolt to identify the strength class. The number of lines on the head of the bolt is two lines less than the actual grade. For example, a grade 8 bolt will have 6 radial lines on the bolt head. Some metric nuts are marked with a single digit strength identification number on the nut face.

The correct fasteners are available through GM SPO. Many metric fasteners available in the aftermarket parts channels were designed to metric standards of countries other than the United States, and may exhibit the following defects:

•	Lower strength

•	No numbered head marking system

•	Wrong thread pitch

The metric fasteners on GM products are designed to new, international standards. Following are the common sizes and pitches, except for special applications:

•

M6.0 X 1

•

M8 X 1.25

•

M10 X 1.5

•	M12 X 1.75

Prevailing Torque Fasteners


(1)	Prevailing Torque Nut, Center Lock Type
(2)	Prevailing Torque Nut, Top Lock Type
(3)	Prevailing Torque Nut, Nylon Patch Type
(4)	Prevailing Torque Nut, Nylon Washer Insert Type
(5)	Prevailing Torque Nut, Nylon Insert Type
(6)	Prevailing Torque Bolt, Dry Adhesive Coating Type
(7)	Prevailing Torque Bolt, Thread Profile Deformed Type
(8)	Prevailing Torque Bolt, Nylon Strip Type
(9)	Prevailing Torque Bolt, Out-of-Round Thread Area Type

A prevailing torque nut is designed to develop an interface between the nut and bolt threads. Distortion of the top of a metal nut or using a nylon patch on the threads in the middle of the hex flat causes that interface.

A prevailing torque bolt/nut that is clean and free of rust can be reused as follows. If there is any doubt, replace the fastener:

Clean away all dirt or foreign material.
Inspect the fastener for signs of overtightening.
Handstart the fastener at the original location.
Inspect the fastener for torque development, referring to the table below.
Tighten the fastener within specifications.

Prevailing Torque Specifications (Metric-Size Fasteners)

Component	Size (in mm)	N·m	Lb in
Nuts and All Metal Bolts/Screws	6	0.4	4
	6.3	0.4	4
	8	0.6	7
	10	1.4	12
	12	2.2	18
	14	3.0	27
	16	4.2	37
	20	7.0	82
Adhesive or Nylon Coated Bolts/Screws	6	0.4	4
	6.3	0.4	4
	8	0.6	5
	10	1.2	11
	12	1.6	14
	14	2.4	21
	16	3.4	30
	20	5.6	50

Prevailing Torque Specifications (English-Size Fasteners)

Component	Size (in inches)	N·m	Lb in
Nuts and All Metal Bolts/Screws	0.250	0.4	4
	0.312	0.6	5
	0.375	1.4	12
	0.437	1.6	16
	0.500	2.4	21
	0.562	3.2	28
	0.625	4.2	37
	0.750	7.0	62
Adhesive or Nylon Coated Bolts/Screws	0.250	0.4	4
	0.312	0.6	5
	0.375	1.0	9
	0.437	1.4	12
	0.500	1.8	16
	0.562	2.6	23
	0.625	3.4	30
	0.750	5.2	49