TRUCK SERVICE MANUAL
Loose engine and main transmission to frame
Main Transmission Companion Flange Vertical
mountings will not affect vertical or horizontal alignment
of the main transmission companion flange with respect
The main transmission companion flange machined
to the flange being 90 degrees to the engine crankshaft
surface must turn in a vertical plane, that is, 90 degrees
center line. However, any change from the originally
to the engine crankshaft center line.
mounted position caused by loose mountings or
otherwise, will result in the remaining drive line flanges
The rear face of the engine crankcase as well as the
working at a different angle, which is not permissible.
front and rear faces of the flywheel housing, bell housing
Therefore, before checking the drive line companion
and main transmission are precisely machined 90
flange angles, be certain that engine and transmission
degrees to the engine crankshaft or transmission
mountings are in good condition and are tight.
mainshaft, as the case may be.
Propeller shaft alignment checking procedures given
Most engines are mounted in the chassis at so many
herein will apply to front as well as rear axle drive lines.
The vertical alignment angle of all companion flanges,
lowered X number of degrees for among other reasons,
whether on the front axle or rear axle drive line, is 90
to minimize the drive line universal joint working angles.
degrees from a true horizontal minus the number of
It follows then, that the engine crankshaft center line and
the main transmission mainshaft center line do not lie in
a true horizontal plane. Since the transmission
Main Transmission Companion Flange Run-Out
companion flange machined surface is 90 degrees with
Because the angularity of the complete drive line
the mainshaft, the actual vertical angle will not be 90
must match with the main transmission companion
degrees but X number of degrees from a true vertical, or
flange, the flange itself must turn perfectly true, and its
in other words, the same number of degrees from a true
exact vertical angle must be known.
vertical that the engine crankshaft center line is from a
To check for run-out of the main transmission flange,
securely mount a dial indicator to the transmission rear
One can now realize the importance of determining
face. Position indicator stylus on the flange machined
the exact, angle of the engine crankshaft center line
surface and rotate flange one complete revolution, Fig.
when checking the main transmission companion flange
Flange run-out must not exceed .005". If run-out is
excessive, it may be eliminated by rotating the flange on
the spline. If excessive run-out still exists, flange is
distorted and must be replaced.
Fig. 11. Measuring Mounted Engine Angle
To determine the engine angle, park the vehicle on a
level surface and disconnect the propeller shaft from the
Fig. 10. Checking Companion Flange Run- Out
main transmission companion flange. Check the flange
for looseness and tighten if necessary.