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Discussion Starter #1
SO I just bought my first diesel and i'm so excited. But I have an issue with hard shifts. I always end up in limp mode and the shifts kick like a mule. At times the tranny just shifts right on through the gears other times the tranny hunts for gear. shifting up and down and it's driving me crazy. I need to figure this out before I damage something likely more expensive than whats causing the problem. Can anyone throw me a bone?
 

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Barometric Pressure Sensor can cause these issues. Located under the dash, easy fix. Mine did the same thing when I bought it. Better to have hard shifts than slow sloppy ones so you're not doing too much damage.

Is your speedometer reading correctly? Needle jumping around?
 

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Discussion Starter #3
Thank you for the response and sorry for the delay. I was tracing down a mystery leak that turned out to be an oil rail endcap. Anyway, I did not know that these trucks had a barometric sensor. I will be looking for that gem immediately. I've heard that the "kick in the pants" shifts are better than the softies, but holy moly. It feels like im getting hit in the back with a baseball bat. My speedo does jump around, sometimes, usually around 65mph or so. and sometimes the mileage display stops working and requires a few fim slaps to work again. I'm thinking that I'll need a POSM repair soon too. Can you direct me a bit to where under the dash that is located.
 

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Discussion Starter #4
Thank you for the response and sorry for the delay. I was tracing down a mystery leak that turned out to be an oil rail endcap. Anyway, I did not know that these trucks had a barometric sensor. I will be looking for that gem immediately. I've heard that the "kick in the pants" shifts are better than the softies, but holy moly. It feels like im getting hit in the back with a baseball bat. My speedo does jump around, sometimes, usually around 65mph or so. and sometimes the mileage display stops working and requires a few fim slaps to work again. I'm thinking that I'll need a POSM repair soon too. Can you direct me a bit to where under the dash that is located.
I replaced the VSS a couple of months ago thinking that it might be the issue. It shifts hard less often, but still too often. But I have a question, I've also heard that "only" the motorcraft VSS qualifies as a good replacement, at the time I bought the less expensive {cheapest} option.
 

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I've got a cheap replacement in mine for now so it should be ok, just limited life span.

BPS is under the dash, look one up and once you know what it looks like it will be easy to spot.

PSOM is on the back of the speedometer. A bad ground can also interrupt this signal and cause weird shifting.

Do you have any tail lights burnt out too?
 

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Discussion Starter #6
I dont believe so. I'll check again tonight. When i first started troubleshooting this, I checked the rear lights and was told to check the 3rd light on the back of the cab. I haven't checked recently. I just know that it seems to be a sensor/connector. I can reset it by shutting down the engine and restarting, but lately i've gotten fancy and use OBDLink app to reset the PCM code 500 (VSS) sensor circuit fault. Man I love this beast. Neighbors, not so much at 1230AM when i get home.
 

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Discussion Starter #7
OK, I figured it out. By accident. When I replaced the VSS, I broke the retention clip on the connector. So, I guess it makes sense that I was having shifting issues as the wire was BARELY plugged into the VSS. I just now remembered that and went out and checked during my break at work. Well, I'll see how she shifts on the way home.
 
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