Join Date: Sep 2008
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Some of you have probably read my previous thread describing a 3rd gear failure in my 5R55S automatic transmission with only 9,500 miles. After doing considerable research using my Ford Service Manual DVD and pestering several transmission builders here is what I have determined. The root cause of the 3rd gear failures is the seal on the intermediate servo piston. By not continuing to drive the vehicle with this failure, the band is most likely not damaged. I spoke with a couple of transmission techs at 2 different Ford dealers and both said they replace 2 to 3 of these intermediate servo pistons a month for this exact reason.
So, I pulled the pan down on my 5R55S. No metal or clutch material and the fluid was not burnt. That indicated the failure may be as simple as a repair and not an overhaul. I investigated the possibility of replacing the intermediate servo piston with the transmission in the vehicle. This is not possible as the transmission is too close to the body. So I removed the transmission. Now here is where transmission shops offer differing opinions. Some shops say this CAN NOT be done without completely disassembling the transmission because when the servo piston is removed, the intermediate band anchor will fall down in the case. Yet others say they replace these components frequently without ever disassembling the transmission. I figured I had nothing to loose. I pulled the intermediate servo piston snap ring, cover, piston/seal assembly and spring. If you will look at the attached picture (the one that is very bright), you will see in the servo piston bore the anchor is still visible. This is good news as it would indicate that the band is not broken and the anchor did NOT drop down when the servo piston was removed. There is also a picture of a new servo piston, with the cover, assembled ready for installation in the case. Lastly, take a look at the piston I removed. Notice on the Small OD a 1.5" section of the sealing lip is completely gone. I now have the intermediate servo piston assembly reinstalled back in the transmission case.
While the transmission was out, I am replacing the TSS sensor as a while back I had a P0715 DTC for that sensor. I cleared the code and it never came back. But to replace the Input turbine speed sensor the transmission must be removed, now was the time to replace the sensor. Tomorrow I will adjust the intermediate and overdrive bands.
How much has this venture cost me - other than a whole lot of my labor:
(1) Intermediate servo piston (1L2Z-7D021-CA) $16.73
(1) Seal - intermediate servo piston cover W702969-S300 $2.60
(2) Band adjustment locknut (XW4Z-71000-AA) $3.60 ea.
Total parts investment $26.53
Now while the transmission is out, I am going to take advantage of this opportunity to install a 2,800 RPM stall converter. Keep in mind this is a daily driver and not a track vehicle.
In conclusion, will this fix my 3rd gear problem? Won't know for sure, but for less than $30 in parts I couldn't justify a complete overhaul yet.
Moral to this story: If your transmission looses 3rd gear don't continue to drive the vehicle.
LinkBack to this Thread: http://www.moddedmustangs.com/forums/2005-2010/90977-any-one-having-shift-problems-5r55s.html
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