I just had my transmission replaced in my 00 323i and the transmission shop did open it up to find the fault of my failed reverse gear.
A couple a noteworthy comments upon opening the 49k ZF tranny. The oil did not look discolored or smell burnt at all. The sponge on the tranny filter was pretty hard and it did have some small metal shavings on it. Don't know if its supposed to be hard by design.
The drum in my transmission that holds the reverse gears is made of aluminum and was broken which lead to my reverse failure. Changing the tranny oil would not have prevented this.
It was my mechanics opinion that abuse on the car would lead to this type of failure but he also admitted that the aluminum drum is weak compared to the steel units in other transmissions he has serviced. He showed me a couple from trannies that he was in the process of rebuilding. He does quite a bit a work on Lincoln's and yellow cabs.
I ended up going with a rebuilt tranny that was purchased from BMW (2yr/unlimited miles) instead of fixing the reverse gear. The slip ring that holds the reverse gears in place was eventually found in a foward compartment and I didn't want to take the chance of having another failure with other gears by fixing the reverse gear.
Now being the third owner of my car, I thought that the previous two drivers could have beaten the car a bit. Beaten, I mean like not waiting for the car to completely stop to shift gears between forward & reverse while parking. I thought to myself that had I purchased the car new, this would have never happened (although the jury could still be out on this). I do drive spirited but careful in not abusing my cars (like all of you).
My conclusion:
I noticed that shifting into gear (D or R) takes a second or two to engage in my X and I am now more aware of this and willing to be a little bit more patient in changing gears. This is not to say that this will avoid a problem but maybe delay it. I will still have my dealer look at it but the key point was to be a little more frugal with the gears in parking my X since my e46 tranny is delicate from experience and costs.
I also think that changing the fliud is still a good idea at a reasonable mileage interval. My X just turned 40K yesterday and I figure now would be a good time since I will keep her for 3 to 4 more years. It may cost me $250 for the oil change but I am buying some piece of mind in extending my trannies life span.
If anything comes out of this, the next owner of my X will also benefit from this and be happy with this fine machine as I was too.
