Need help with 4r70w Output Speed Sensor (OSS) | Ford Explorer Forums - Serious Explorations

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Need help with 4r70w Output Speed Sensor (OSS)


High Voltage.
Elite Explorer
February 2, 2002
Reaction score
Year, Model & Trim Level
1998 Mountaineer AWD
Does anyone know what the actual function of this sensor is? It's not the same as the vehicle Speed Sensor (VSS), and my speedo works like it should. Does the OSS tell the tranny what gear it should be in? I used a scan tool, but don't recall the code it gave, and now the scanner is on the fritz. I know for a fact it said OSS-output speed sensor, and not vehicle speed sensor. My Mountaineer has the CEL on and it shifts like it is in Limp mode, but there is no Flashing OD light, just the CEl, and the single Output Speed Sensor code. I called 2 different Ford dealers and they didn't have a clue, and told me I needed to bring it to them an d let them look at it :rolleyes: Not going to happen. The only time my vehicles see the dealer is when they are new, and when they get traded in. If I have to there is a transmission shop I have some faith in, but I'd rather figure this out with some help of the wise members here :) :shamelessattemptatsuckingup: Anyone have any ideas?

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Alright, so I've done some digging and learned that the OSS is in the tailshaft of the transmission. How hard is this to get to? Does the trans stay in the truck?

look at the "My 4R70W Rebuild Diary"... as we speak the last pix are of it. An 8mm smallish bolt removed and it pops right out..... go look....... easy replacement. (There is a pic of the parking pawl that shows the OSS inside the case too. Ford Part #F4AZ-7H103-A. It is NOT in the tailshaft housing but near the rear of the case on the driver's side... I have a "used" one for sale <joking>.

You know, I forgot all about the 4r70w diary, although I did recommend your a4ld diary to a member in the chat today :) I've been busy and put off reading the 4r70w thread, and I'm sure all of the info I will need will be in there. Thanks a bunch. If I get stuck on something I'll have to bug you again :confused:

Well here's some pics in case they help.... Here is my new one, still in the package.... cost me $16, not including tax...


Here it is, virginal - never been hot yet... (can I say that on EF?)


Here is the connector. Word of advice, get some dialectric grease and keep it in your on lots of electrical connectors.... and this a good place for it before you assemble the connector, Helps prevent corrosion... (lube the two O-rings with ATF before your assemble it too (or with vaseline if you are kinky)).


You kick ass. I read through the 4r70w diary, and actualy learned a bunch. Now if only I can retain it :) I'm surprised it was so cheap. I called 2 different dealers and they couldn't figure out what sensor I was talking about :rolleyes: Maybe with the part, the part number, and a sacrificial lamb I will have some better luck. I will try and get one after work today. Thanks a whole bunch :)