Failure phenomenon: a 2007 annual Passat 2.8 L sedan, mileage 80000 km. When the vehicle speed reaches the user reflect the 140 ~ 160 km / h, the steering wheel and the vehicle body can be clearly felt jitter, similar to tire balancing failure caused by jitter.
Check Analysis: When I take the car, first road test found that when the vehicle speed reaches 140 km / h, the above-described failure began to appear, the vehicle speed reaches 160 km / h, the most serious failure phenomenon. Firstly, the author of the whole car four tires were carefully checked and found no rim and tire damage occurred and subsequently for four tires posterior dynamic balance calibration test, fault still; check the front and rear axle and pouches, front axle stability bars and pouches, pouches only a stabilizer bar is damaged, but the damage has nothing to do with the failure of the sleeve (the sleeve when the overhaul has been replaced); check the front and rear wheel bearings, without damage to the phenomenon. I suspect part of the chassis were not found to the question of whether the fault associated with the engine? In order to determine the point of failure when a failure phenomenon of the road test, the shift lever to the neutral position, this time, the fault is not eliminated. Thus it concluded that, regardless of the engine failure, the fault point can be locked in the chassis section. Consider first shaft to the transmission and, when the transmission path is very smooth lifting gear test, and there is no abnormal sound, so there is a possibility of failure can be ruled out, check around the drive shaft and no damage and significant deformation.
After the examination, because the difference between the author suspected fault is caused by the vehicle running stability, then analyzed the data diagnosis based on the wheel alignment. Effect of wheel alignment parameters of the vehicle is a front wheel camber and toe-in, the author of the vehicle wheel alignment check, the following data (Table 1).
Table 1
The data in Table 1 show that although the data of each group are within the standard range, but the value is too large camber in order to verify whether the value associated with the fault, the author of the vehicle made the following modifications: the front of the front axle to remove the two fixing bolts, between the front axle and the vehicle body mounting portion at each of two bolts plus a thickness after approximately 2 mm spacer, the fixing bolts, and then re-adjust the wheel alignment, the adjusted values are shown below (table 2).
Table 2
As can be seen from Table 2, significantly reduced after the addition of inclination front gasket, substantially unchanged other data. In this case, the author re-road test, when the vehicle speed reaches 140 km / h, the fault is eliminated, when the vehicle speed reaches 160 km / h, can feel a slight jitter, the jitter does not feel the steering wheel, the fault is corrected.
Review Summary: The author later with a special road test a few more Passat, found in vehicle speed 140 km / h or more, there is a slight jitter, but did not shake the failure of the vehicle’s serious. Based on the review of the repair process analysis, I believe this may be due to the car before the vehicle suspension parts had been more serious external shocks, resulting in hard to change after the front wheel caster angle, resulting in failure of the above vehicles at high speeds.
(Lu Chuanping)