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Faulty Neutral Safety Switch?

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Old 05-04-2012, 07:49 PM
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Faulty Neutral Safety Switch?

Just had my '91 7.3 IDI F250 inspected and they gave me a laundry list of problems. No idea how it passed last year for the previous owner, but whatever...

On top of the list appears to be a faulty neutral safety switch (the truck starts in any gear).

I've been reading threads for a few hours now and I am mightily confused.
1. Is the Neutral Safety Switch on my truck the same thing as the MLPS?
2. Will I find it on the driver's side of the tranny? (Until today, I was 99% sure the truck had the E04D tranny, but a new one was put in before I bought it and I suppose it could be the C6? How would I know?)
3. Does it look like this?



4. Would this also explain not having tag lights or back up lights? Or are those separate problems.

Thanks!
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Old 05-04-2012, 07:58 PM
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yes that is the mlps/transmission range sensor/NSS.

yes it will be on the driver side of the tranny. can't miss it.

how many shifts do you feel?
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Old 05-04-2012, 08:07 PM
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Good question. You mean when I get up to speed, yes? I think three, but I would have to drive it tomorrow to be sure.

What would that indicate?

Thanks.
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Old 05-04-2012, 08:15 PM
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Forgot to mention the truck is automatic, if that changes anything.
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Old 05-04-2012, 08:25 PM
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so you put the truck in drive. you are now in 1st gear, you start rolling, it shifts, that is 2nd, then some more speed and rev increase, another shift, that was the shift into 3rd gear. so if you have a c-6 then you will only feel/see two shifts.

now if you have the E4OD, 1st gear & 2nd gear will be the same as above. then you will hit 3rd, then you will feel a kind of half shift. that is the torque converter locking. then you will get another shift. that is overdrive. then another half shift=torque converter lock.

i hope i got that right lol
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Old 05-04-2012, 08:49 PM
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Quote:
Originally Posted by '94IDITurbo7.3 View Post
now if you have the E4OD, 1st gear & 2nd gear will be the same as above. then you will hit 3rd, then you will feel a kind of half shift. that is the torque converter locking. then you will get another shift. that is overdrive. then another half shift=torque converter lock.

i hope i got that right lol
close.
just there isn't another lockup shift felt after OD.

sensibull,
if you have the 3 speed C6,she'll sound like she screaming all the time over 45mph.if you have an auto with an OD,then she'll be low rpms even at 55-75mph.
pretty hard to confuse the two trans.they're drastically different.
if you just see no OD light/switch.0whatever they did in late 80's -'91 then just count the trans pan bolts,or look at the trans code on the drivers side door jam sticker.
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Old 05-04-2012, 08:51 PM
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Quote:
Originally Posted by FORDF250HDXLT View Post
close.
just there isn't another lockup shift felt after OD.
so the converter stays locked during the shift into O/D?
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Old 05-04-2012, 08:57 PM
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Quote:
Originally Posted by '94IDITurbo7.3 View Post
so the converter stays locked during the shift into O/D?
no it doesn't.but the driver never knows.it's far,far,far to fast to feel.
downshifting from OD into 3rd however......that brief unlock state is felt,before locking back up.thats there to help provide a little extra grunt to tow the load uphill.it also helps spike that boost gauge!
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Old 05-05-2012, 07:34 AM
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Thanks for the replies guys. I can drive 60 without screaming or high RPM so I guess I have the E04D.

Any reason I shouldn't go with an aftermarket replacement from some place like Advance Auto on this part?
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Old 05-05-2012, 09:08 AM
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OK, I'm a little more confident in what I am doing know. Here's the pertinent info & diagram for this part, just in case it might help someone in the future.



Part numbers (as best I can determine)
Again, this is for a '91 7.3 IDI F250 with E04D

Ford: 7A247 (They're calling it "Auto Trans Gear Position Sensor")
Autozone: F433 ("Neutral Safety Switch" made by Duralast)
Advance Auto: S9192 ("Neutral Safety Switch" made by BWD)
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Old 05-05-2012, 09:32 AM
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ok now that,that is established.

1. Is the Neutral Safety Switch on my truck the same thing as the MLPS?
2. Will I find it on the driver's side of the tranny? (Until today, I was 99% sure the truck had the E04D tranny, but a new one was put in before I bought it and I suppose it could be the C6? How would I know?)
3. Does it look like this?
4. Would this also explain not having tag lights or back up lights? Or are those separate problems.

1.yes it is.
2.yes about midway.
3.yes it does.
4.yes it could explain not having backup lights.running lights/brakes lights im pretty sure will be a separate issue though.

in '95 they updated the plug for this.the replacement MLPS will need to be re-pinned if it hasn't already been upgraded.
thats why you see the pic with different plugs on the end in the pic at autozone for example is a good one.
you'll know if it's been updated because the replacement part will simply plug right in.if it doesn't,your in for some tedious fun lol.
info to help you re-pin it if needed to latter style plug to keep out moisture is here;
http://www.fullsizebronco.com/forum/...d.php?t=191742

Last edited by FORDF250HDXLT; 05-05-2012 at 09:43 AM. Reason: direct link
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Old 05-05-2012, 10:24 AM
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Wow, thank you, that link is hugely helpful, especially if I have to re-do the pins.

[Edit: I also stumbled upon this link, which is essentially the official Ford document explaining this updated pin/connector and how to update the old one]

At the risk of exposing myself as a complete newb, my F250 doesn't have a removable tunnel cover, right? I have to do this repair from under the truck?
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Old 05-05-2012, 10:29 AM
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hmmm.good question.it's been a while since iv been in there to sound proof my floor board,and iv always driven manual shift trucks in the past,but i think there is a bolt on cover just the same under the carpet/mat for the auto trucks.im sure it's cheaper to make the cabs all the same,and plate the hole solid or with an opening for the stick.
if im right,and im pretty sure thats how it works,it would be well worth the effort to do it from up top that's for sure.
i re-pinned mine (low mile truck.i replaced/updated it before it failed) from the bottom,and if i had to do it over again............

if your truck has some miles on it,it's likely it's all been updated years ago and new sensor will just plug right in.so don't worry too much until ya find out.
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Old 05-05-2012, 10:46 AM
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Looks like my tunnel cover is removable (just lifted the carpet), but to pull it back far enough I'd probably have to remove the whole front bench seat. Seems to me swapping out the neutral safety switch from the top or beneath would be just about the same hassle... but if I have to re-do the pins that's where the ease from the top comes in?
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Old 05-05-2012, 10:55 AM
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yeah that's right.and depending on if you have heat or not to warm up some potentially seized up seat belt or seat mount bolts,it may be easier to stick with the bottom lol.
right,to swap it is nothing.you do nothing but unplug,and plug in the new all from the bottom and done.
if you need to re pin it........i suppose the easiest thing to do overall,would be to unplug the solenoid pack plug
(the wire plug on the other side of the trans) unclip the harness in the back,and bring that whole harness down around the trans,to bring the wires right down nice to work on.without doing that,the wires are just too dang short and make the job needlessly miserable.
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