Can dirty fluid cause an automatic transmission to thump when in gear?

Answer 1

Usually Transmission Fluid is not changed til 100,000, so not a likely reason for rough shifting. I just had to change the "turbine shaft speed sensor" (Ford name for it) in my 1998 Contour. When checking on line, there are hundreds of people, all makes of vehicles, with the same problem. It is also called "Speed Shaft Sensor" and probably a few others. My engine is 4 cyl & in sideways in this Ford. It has a "transaxle" transmission system & the "turbine shaft speed sensor" is on the driver's side behind the front tire. I can see it if I turn the steering wheel as far to the right as possible. Jt attaches to the transaxle (which is round shaped on the end I am viewing thru the wheel well) & is located about the 3 o'clock position. Attaches w/ a single 8mm bolt which is torqued on pretty tight. Then you must pry it out. This part has a rubber oring around the stem that goes into the transaxle so it is a matter of pushing it into the hole evenly until flush with the base of the sensor. Flat screw driver & patience to wedge the old one out.

Sorry for the lengthy explanation, but no instructions come with this nasty little (very necessary for shifting) part. Mine was damaged when my tire blew out. It caused some nasty,rough shifting from 1st to 2nd. Felt like tranny was going to jump out. Let off gas just b4 car is shifting to 2nd, it helps until you fix it.