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Discussion Starter · #1 ·
I have been trying several things lately to try and isolate a problem I'm having with my 99 Taurus shifting occasionally. Every once in a while the car will be driving just fine and as I go to accelerate it will feel like it slipped into neutral and goes from neutral to drive and back repeatedly. Or at least thats what it feels like. When this happens I have a hard time getting the car to go over 1800-2000 rpm without slipping. Once the car is shut off and restarted it usually goes away for awhile. Happened the other day on the expressway with the cruise set at 75mph, humming along then felt like it went to neutral and just coasted in front of a semi, and took me 20 seconds or so to get it to catch and slowly pull away from his front bumper.

I have had the trans fluid and filter changed and since then have been trying different ways of driving to see if I can duplicate the problem. If I drive like old man Muntz, all good, a little more gas still good. Go anywhere near WOT, revs right up and won't shift at all till I back off a bit.

Last night I was messing around on my way home and got to an area where its downhill towards home for miles, so I put it in Neutral to coast. The car lost its damn mind. It immediately jumped to 3500 rpm in Neutral. When I put it back in Drive, it fell to 500 rpm before bouncing back to 2000. When I tried giving it some gas, it revved right back to 3000, then suddenly went back into gear and dropped to 2000 again, and seemed fine from there. Same thing happens anytime I put the car in N while moving.

Any ideas where to start?
 

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Sounds like classic VSS failure symptoms. It's on the passenger side of the trans, above the exhaust and near the firewall under a heat shield. Can be a major PITA to remove from a Rust/Salt Belt car, but it can be done. The risk is in trying to pry/pull it out if it's stuck, if the plastic gear part breaks off in the trans., then the trans. has to be removed to get the broken piece out.
 

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Good to know, mine does the same and I had not suspected the VSS due to the fact that there was nothing wrong with cruise control and no fluctuations or false readings in the speedo. I was actually leaning more to the transmission range switch.
 

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You can access the vss on a 99 tec with ax4n by reaching blindly down directly between the evr (egr solenoid on pass. side of uim) and firewall. Pull up foil open-ended heat shield, unplug vss, remove 10mm retaining bolt with a 1/4 in. dr. ratchet, 2 long exts. and 10mm socket. Pull vss from tranny. Install is reverse of removal. All work performed blindly and by feel. You can purchase borg-warner vss from advance auto or oreilly for $20-25. Almost a maintenance item on a 99 tec. Ive had to change 5-6. Only one had speedo issues. Others illustrated slipping 1-2 shifts and other erratic shift point problems. None threw a code. 84FordMan, on your 03, vss is called an oss (output shaft speed sensor). Ford changed the name in 2000. Still the tranny output sensor. Tss (turbine speed sensor) is the tranny input sensor.
 

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^^^ Sheila, you have obviously never had a seized up one? I have never had one that "just pulled out", even when I have followed the Factory method of dropping the exhaust front Y pipe. You must be lucky!
 

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Discussion Starter · #11 ·
Is there a reasonable way, like with a VIN or something to figure out which VSS I need? There seems to be a ton of them, depending on speedo mechanical or electronic, and AX4S or AX4N
 

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You need the bwd#S8318 from oreilly ($24.99) or advance auto ($33.69). Both lifetime warr. Or the duralast (wells) #SU1067 from autozone ($19.99). 2 yr. warr.
 
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