KiwiME
Well-Known Member
Well, from that very useful information I can see that the Hyundai/Kia gearbox is virtually identical in design to the Nissan Leaf. The only difference I can see is that ours is missing one locating diameter at the end of the motor shaft spline and there is an added static O-ring seal at the ~80mm dia flange where the dark red area/blue arrow is on the gearbox picture. Between this design and the Nissan, lube oil will more easily access the motor spline via the tail bearing and the hollow pinion shaft, and that can only be good.
Trying to predict potential areas of failure is very speculative without having precise dimensions to carry out a stress analysis, or better, viewing a damaged example. These observations are based on the noise being reported as motor-shaft frequency, that dirty oil has been reported, and what would concern me just from looking at the design if it were my own:
1. First stage pinion shaft (pink):
2. The first and second stage shafts all use ball bearings and will be shimmed at assembly for near zero endplay, just like many other EV gearbox designs. The second stage pinion shaft (in orange) will see minimal end thrust due to the helical gears pushing axially in opposite directions under torque. But the first stage shaft (pink) will see significant end loading under torque, but I can only assume that the bearings are sized to suit. But bearing damage here could deteriorate quickly due to the high RPMs involved.
Excess end play on any of the three shafts will make clicking noises or clunks but only when torque direction changes, or at least not regular in timing. To get a clicking once per motor rev means it has to be at the first stage shaft and from localised damage, either a bent shaft, damaged female spline or if the bearing near that area (arrow b) fails and leaves the motor shaft to support the radial load.
Trying to predict potential areas of failure is very speculative without having precise dimensions to carry out a stress analysis, or better, viewing a damaged example. These observations are based on the noise being reported as motor-shaft frequency, that dirty oil has been reported, and what would concern me just from looking at the design if it were my own:
1. First stage pinion shaft (pink):
a) The wall thickness along the entire shaft looks quite thin, especially as it has splines at the motor interface and parking pawl (green thing). Stress cracks could develop in the motor interface's female spline under torque, or be present at the start from production machining stresses on either spline.
b) Normal metal debris from the parking pawl could go straight into the adjacent ball bearing and damage it, if it has an open cage. Often bearings used in manual gearbox applications are equipped with a single shield at the gear side to avoid this problem. That allows oil to enter but not chunks of steel. No shield is shown but the CAD model may not show such a minor detail.
b) Normal metal debris from the parking pawl could go straight into the adjacent ball bearing and damage it, if it has an open cage. Often bearings used in manual gearbox applications are equipped with a single shield at the gear side to avoid this problem. That allows oil to enter but not chunks of steel. No shield is shown but the CAD model may not show such a minor detail.
2. The first and second stage shafts all use ball bearings and will be shimmed at assembly for near zero endplay, just like many other EV gearbox designs. The second stage pinion shaft (in orange) will see minimal end thrust due to the helical gears pushing axially in opposite directions under torque. But the first stage shaft (pink) will see significant end loading under torque, but I can only assume that the bearings are sized to suit. But bearing damage here could deteriorate quickly due to the high RPMs involved.
Excess end play on any of the three shafts will make clicking noises or clunks but only when torque direction changes, or at least not regular in timing. To get a clicking once per motor rev means it has to be at the first stage shaft and from localised damage, either a bent shaft, damaged female spline or if the bearing near that area (arrow b) fails and leaves the motor shaft to support the radial load.
