(Toyota prius) Troubleshooting a BMW Transmission that Will Not Go Into Reverse
No commentsBy Astonish Articles
An automatic transmission is just that- automatic, consequently most people tend to pay very little attention to it until a major problem rears its ugly head.
Picture the scenario- you are driving along in the lap of luxury, the satellite radio blaring and the heated seats on. You have become accustomed to the comfort level and great driving experience brought to you by BMW.
You decide to stop at the local convenience store on your way home to grab some ice cream for the kids and a bottle of water for yourself. Upon returning to your car, you start it up, check your rear view mirror, put the shifter in reverse and then the unthinkable happens- the engine just revs as if it is in neutral and the car goes nowhere!
This article deals with the reasons behind an unexpected loss of reverse in certain BMW automatic transmission equipped vehicles, specifically 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 some others built in the 1999 to present model years.
To eliminate confusion, this does not apply to vehicles equipped with the GM 5L40 E transmission, just the ones with the sometimes problematic ZF5HP19. The 5L40 E has some issues of its own that are beyond the scope of this article but are certainly going to be the subject of another.
The failure rate for these transmissions seems to be very high and is expected to become much more of a problem as time goes by.
Typically, the vehicle is working perfectly while driving forward but when it is put in reverse there is a complete and permanent loss of movement to back up.
Reverse is typically a major feat for any transmission to accomplish- imagine the demands that are placed on a gearbox as it is asked to reverse the torque of your engine so that you can back up your nearly 4000 pound vehicle.
By far, the most common cause of the reverse problem in BMW’s is the failure of the D-G clutch drum. Specifically, the snap ring that retains the D or reverse clutch breaks out of the clutch drum resulting in an inability for the clutch pack to apply.
The good news is that there is hope in regards to a proper repair. The factory has released an updated part that so far appears to be a permanent fix for this problem.
In our testing and in conjunction with several hundred successful repairs at our facilities, the new part seems to be metallurgically superior in several ways.
We have found that there is an improved radius area as well as slightly thicker casting. In addition to this, the grove that retains the snap ring is also relocated further away from the edge of the drum.
With this issue addressed and attention to detail in several other areas of the ZF5HP19 unit, the transmission can be repaired to “better than new” condition by a competent transmission rebuilder / remanufacturer. In fact, when properly repaired, the ZF gearbox becomes quite robust and can provide an almost indefinite service life.
For more information on Car Transmissions or to find a Used Transmission visit SWTransmissions.com
Grinding Valves in Antique Cars
By Peter Salmonford
Owing to the fact that the inlet valve is not subjected to the temperatures which the exhaust valve reaches, it is very rarely necessary to grind it in. The period at which valve grinding becomes necessary varies with different engines and the care of driving, etc. Roughly, with a water-cooled engine, the exhaust valve should be ground in after 3,000 miles and the inlet after 6,000. No harm can be done by grinding in a valve, so that if an engine loses power before it has run this distance it is well to examine the valves and give them a slight grinding. After the valve is replaced the cotter should be readjusted, and locked by means of the nut.
If a valve is badly burnt examination will show whether it is better to fit a new valve rather than grind in the old one. Very often a badly burnt valve can be recut and trued, and to replace the whole process of valve grinding, a process of valve truing and an apparatus for carrying it out has been evolved by the Southern Automobiles, Ltd. The apparatus consists of a pair of cutters, one of which recuts the valve face after it has been removed, whilst the other has the same effect on the valve seating. Into the respective merits of the two processes it is not proposed to enter, but valve grinding is the more common practice, and it can be applied not only to the main engine valves, but to other valves when the need arises. Thus a petrol or water tap sometimes leaks slightly, when it should be removed and the removable part ground in with some fine emery powder.
It will have been gathered that grinding-in of valves is done to restore loss of compression, but this weakness is sometimes due to other causes. For instance, any one of the cylinder joints may be leaking. The sparking plug washer and that upon the valve cap which screws into the opening sometimes leak, and to ascertain if this is the case some paraffin should be squirted round these washers and the engine turned round just to come on to the compression stroke. When pulled slowly over the compression stroke the presence of bubbles will indicate if there is any leakage at these points. If there is leakage new washers must be used. On no account should any adhesive mixture, such as boiled oil or gold size, be put on the screw threads. This is sometimes done to obtain good compression, but it is inadvisable, on account of the extreme difficulty in separating the parts later.
Peter Salmonford is a keen fan of cars, and likes to write about antique and modern vehcles. Take a look at his other articles on hydrogen conversion, the benefits of an electric car kit and using browns gas in your own car.
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Friday, November 14th, 2008 at 11:45 pm and is filed under automotive. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
