V 2500 P/U 4WD V8-350 5.7L (1987)
Tires: All Technical Service Bulletins
Driveline - Tire and Propshaft Speed Reference Chart
GMC NUMBER:
88-T-29
GROUP:
OA - General Information
DATE:
August, 1987
CORPORATE
NUMBER:
860103
SUBJECT:
TIRE AND PROPSHAFT SPEED REFERENCE CHART
MODELS:
ALL LIGHT DUTY TRUCKS
Reed Tachometer usage requires calculating the speed of rotating components on a vehicle and relating it to the frequency of a vibration (reference GMC
Truck Service Bulletin 87-T- 9/Chevrolet Dealer Service Bulletin 87-139 and film #87-404 for Reed Tachometer usage instructions). The chart below
was developed to simplify calculating driveline and wheel and tire RPM.
The procedure for using this chart is as follows:
^
Determine the vehicle tire size and rear axle ratio.
^
Drive vehicle and note the speed range that the vibration occurs at and the vibration frequency (using a Reed Tachometer).
^
Locate the tire size in the first column that corresponds to the vehicle tire size. Select the speed range that the vibration occurs in and note the tire
RPM.. For example, a P215/60R14 tire turns 792 RPM at 55 mph.
^
Calculate the propshaft RPM by multiplying the tire RPM by the rear axle ratio. For example, 792 (tire RPM) X 3.08 (axle ratio) = 2439 propshaft
revolutions per minute.
^
Relate the vibration frequency to the speed of the propshaft or wheels and tires. For example: A first order tire vibration in the above example
would excite the 800 CPM reed on the Reed Tachometer.
