I’ve just read some sage advice from the most savvy BMW tech I know to exist, on the Web; a gentleman who goes by Shogun. And yes, he does live in Japan. Someone was having issues with his automatic transmission, and Shogun opined:
“Maybe a valve body problem. Have you removed the valve body and cleaned it and checked all the small balls and orifices. And especially the solenoid valves inside valve body!!!!”
That got me thinking. So I poked around on the Web some more, and found a nice article on the website for Transmission Repair Cost guide, titled “Transmission Solenoid: Symptoms & Replacement Cost.”
As I understand the article, the owner serviced the valve body and the automatic transmission is now noticeably happier albeit still not perfect.
The author also makes the point that old, dirty fluid can cause the valves to stick, and since many Audi A6 cars have NEVER had an automatic transmission service, that might well explains the problems on my Audi A6 project cars.
Officially, according to Audi, that transmission doesn’t need service. According to the transmission manufacturer, it does. To me, the latter opinion carries more weight.
Another article on MyAutomaticTransmission.com ties slippage to the same problem:
“SLIPS OUT OF GEAR WHEN WARM
SYMPTOMS: Transmission slips out of gear intermittently when engine warms up
CAUSE(S): Internal seals or valves allowing fluid to pass causing pressure loss
REPAIR: Transmission Rebuild or Replace”
That same website also has an article that explains how the same symptoms might be caused by issues that require a rebuild, as well as issues that don’t require a rebuild. The article lists nine things to investigate before giving up hope, and deciding to do a rebuild. These items make a lot of sense to me.
Several of these tie back to the transmission fluid not having been changed, so I have ordered some more transmission fluid, and I plan to do a project car service soon: fluid and filter change.