Bronco L6-300 4.9L VIN Y 1-bbl (1983)
Drive/Propeller Shaft: Customer Interest
Driveshaft - Moan at 35 To 45 MPH
Article No. ^
NOISE - POWERTRAIN "MOAN" AT 35 TO 45
87-15-11
MPH/56 TO 72 KM/H - DRIVESHAFT WITH
DOUBLE CARDAN U-JOINT
^
DRIVESHAFT - DOUBLE CARDAN U-JOINT - POWERTRAIN "MOAN" AT 35 TO 45 MPH/ 56 TO 72 KM/H
LIGHT TRUCK:
1983-87 BRONCO
ISSUE:
A powertrain "moan" at about 35 to 45 mph (56 to 72 km/h) may be caused by high break-away torque efforts of the double cardan U-joint
"moan" is more noticeable in vehicles with AOD transmission while operating in third gear or in vehicles with manual transmissions while
operating in fourth gear.
ACTION:
To correct this, use the following service diagnostic procedure. To determine if driveshaft replacement is required.
1.
Remove rear driveshaft.
Figure 12
2.
Check the double cardan rotation break-away torque by attaching a fish scale, or similar measuring device, to the U-joint
attachment bolt hole located on the half round driveshaft yoke, see Figure 12.
3.
Pull on the fish scale, or similar measuring device, until the U-joint begins to rotate. Notice the force required to revolve the
U-joint.
NOTE:
Rotational effort should be measured in two (2) directions. Both efforts must be within the 3-14.5 lbs. (1.4- 6.6 kg.) specification. The two (2)
directions are 90~ apart and both measurements are necessary when dealing with the two (2) different axis of the U-joints that make up the
double cardan joint.
4.
If the break-away torque exceeds 14.5 lbs. (6.6 kg.) in either direction, tap the ears of the double cardan U-joint weld yokes with a brass hammer.
This will cause the bearing cups to reseat themselves and should result in reduced U-joint rotational break-away torque efforts.
5.
Recheck rotational break-away torque by repeating Steps 2 and 3.
6.
If rotational break-away torque effort is within specification, reinstall driveshaft.
7.
If rotational break-away torque effort is not within specification, or if the powertrain "moan" continues, install a new service driveshaft.
Refer to the driveshaft application chart on page 39 of this TSB for the correct service part number.
