The recent trouble with the Fiat 500e is a good reminder that proper assembling and repair procedures are critically important when working on a car. That is why it is necessary to have access to a factory repair manual for whatever vehicle you are working on. In the case of the Fiat 500e, it appears that incorrect handling of the fasteners attaching the half shafts to the drive flange compromised the chemical locking material applied to the bolt (Lock Patch) resulting in the possibility the bolts may loosen during operation. A supplier applied a different type of Lock Patch to these fasteners than was expected by Fiat and may have contributed to the issue.
All car manufacturers have specific procedures that need to be followed when installing inner CV Joint fasteners and it is crucial that they are followed for safety reasons. Below are the proper installation procedures recommended by Fiat for handling these special fasteners and are posted in the interest of safety for those working on the new Fiat 500e.*
The six bolts and washers that are used to secure the halfshaft to the electric drive unit output flange MUST be replaced. DO NOT REUSE THE BOLTS OR WASHERS.
NOTE: No torque verification is allowed after 10 minutes of the bolts being torqued. ANY MANIPULATION of the bolts after 10 minutes of being torqued will require the bolt(s) and washer(s) to be changed.
NOTE: The inner tripod joints are designed with a retention feature that prevents the tripod rollers from coming out of the inner joint housing up to a specific load. If this feature is overcome and any of the rollers are pulled past the retention feature the joint will “lock-up” and no longer function properly. The entire halfshaft assembly must be replaced if this occurs.
Number 1 is the Fiat 500e Halfshaft assembly. Number 2 is the inner CV Joint Fasteners that attach the halfshaft to the drive flange. There are two halfshafts on the car, left and right, and they connect the front wheels to the transmission on the car. These halfshafts transmit the power of the motor to the wheels.
1.Clean dirt and moisture from the bearing hub before
installing the halfshaft into the hub bearing and
2.Remove any grease from the CV joint threaded holes.
Clean and dry the threaded holes to allow the thread
patch to adhere properly.
3.Place the halfshaft in position on electric drive unit
4.Install the NEW bolts and washers to hold the inner
CV joint to the electric drive unit output flange. While
holding the joint flush to the flange, tighten the bolts
in a star pattern to 30 N·m (22 ft. lbs.).** Make sure the
joint is tightened down evenly to keep the joint flush
to the flange.
NOTE: Make sure the double washer is flush to the CV joint housing prior to torquing the bolt to avoid damage to the washer.
NOTE: Residual torque check allowed only within 10 minutes of being torqued the first time, any manipulation after this time will require a bolt and washer change.
5. Install the outer CV joint into the bearing hub.
Install the 2 lower strut bolts and other components removed.
Refer to the Fiat 500 repair manual for the rest of the procedure.
Note: Using a 36mm thin-wall socket, tighten the hub nut to
310 N·m (229 ft. lbs.).
*These procedures are posted for informational purposes. Always check with the manufacturer for the latest procedures.
**Update 10/14/14: New torque specs updated by Fiat 10/1/14. Previously 26 N·m (19 ft. lbs.).