Have you had the trans filter replaced? The filter, if very dirty, can cause problems.
Also, there are seals / O-rings in the trans / valve body that get old and dry out. When that happens, it allows fluid to bypass and requires a longer period of time to actually work.
Let me know what you find. Also, are there any codes in the computer?
Wednesday, October 8th, 2008 AT 1:39 PM