An automatic transmission is just that – automatic, as a result most people normally pay very little focus to it until a big issue rears its ugly head.
Imagine the scenario – you are driving along the road, the satellite radio blaring and the heated seats on. You’ve become accustomed to the comfort level and excellent driving experience offered you by BMW.
You decide to stop over at the local convenience store on your way home to get some ice cream for the kids and a bottle of h2o for yourself. Upon coming back to your vehicle, you start it up, inspect your rear view mirror, put the shifter backward and afterwards the unspeakable happens – the engine just revs as if it remains in neutral and the car goes nowhere!
Reasons For Transmission Problem
This short article takes care of the reasons behind an unanticipated loss of reverse in certain BMW transmission equipped cars, especially the 3 series and 5 series vehicles that use the ZF5HP19 or “steptronic” transmission. This includes the popular 323i, 323ci, 325i, 328i, 330i, 525i, 528i, 530i, X3 and X5 models well as other integrated in the 1999 to present model years.
To deal with confusion, this doesn’t apply to vehicles equipped with the GM 5L40 E transmission, just the ones with the sometimes problematic ZF5HP19. The 5L40 E has some challenges of it’s own that are beyond the scope of this short article but are certainly intending to be the subject of another.
The failure rate for these auto transmission seems to be very high and is expected to be much more of a problem as time goes by.
Normally, the car is working perfectly while steering forward but when it is put in reverse there is a complete and permanent loss of movement to retreat.
Reverse is generally a major feat for any transmission to accomplish- think of the demands that are put on a gearbox as it is asked to reverse the torque of your engine so that you can reverse your nearly 4000 pound automobile.
Failure of D-G Clutch Drum in Transmission
Without a doubt, one of the most common root cause of the reverse trouble in BMW’s is the failure of the “D-G” clutch drum. Particularly, the snap ring that retains the D or reverse clutch breaks out of the clutch drum resulting in a failure for the clutch pack to apply.
The good news is that there is hope in relation to a proper repair service. The factory has released an updated part that thus far seems to give a permanent fix for this problem.
In our testing and in conjunction with several hundred successful car repairs at our facilities, the brand new part seems to be metallurgically superior in several ways.
We have discovered that there is an improved radius area as well as slightly thicker casting. Along with this, the grove that retains the snap ring is also relocated further away from the edge of the drum.
Having this issue addressed and focus on detail in several other areas of the ZF5HP19 unit, the transmission can be fixed to “better than new” condition by a competent transmission rebuilder/ remanufacturer. Actually, when properly repaired, the ZF gearbox becomes quite robust and can provide an almost indefinite shelf life.