There should be codes.

 

There werent any, none that were stored and none that were current. Today the problem hasn't happened again. I wonder if the VSS might be going out. This truck sat for 3 years, only went 38 miles in that three years ago, and I have only put around 300 miles on it. It only has 97K miles on it.

 

Well still has not happened again... makes me curious...

 

get under your truck and check the plug on top of the differential, that is connected to the speed sensor. if it gets loose (happens easily, happened to me) it will cause the o/d light to flash and the truck will shift insanely hard and wrong. (if it goes haywire again-->) try shifting it manually from first to second and second to drive, if in doing so it shifts alot smoother and softer than it does automatically then it very well could be that loose speed sensor plug or a bad sensor itself...or a couple other things. this happened to me too though. a 2X2 had gotten down in the gooseneck hitch, grabbed the wire and pulled it loose.

is your speedo working?

 

Speedo works fine, my last truck has a boucning Speedometer when the VSS went bad, but I will see what it looks like underthere tommorow and make sure nothing is loose.

 

I've got the same prob going on with my super duty but only after 20-30 mins of driving on a hot day in texas. Hummmm guess I'm getting under the truck next day off to check it out on the rear diff. Whats the VSS ??? Is it the solnoid on the trans?

 

On our 351 auto we had it would shift hard, then spedo maxed out and the milage went blank.. Then the OD light flashed.. Turned out to be the speed thing in rearend

 

well i went and drove the truck tonight to see if I could get it to do it again... Only did it once. And as soon as it did it I was do 45 or so and had just romped on it hard to get around a car on an on ramp. So instead of doing a manual shift into 2nd, i hit the overdrive button and it went away... Im thinking its the VSS at this point.

 

Is there a way to actually test the vss. Like checking it with an ohm reader

 

You could, but you have to read the signal while in motion, which is a little difficult I think.

 

Well I saw a video about measuring the ac current using a drill. I just didnt know if measuring the ohms would tell if it was bad or not

 

You would need an oscilloscope to check it. It uses a flying magnet pickup and sends a signal, not a resistance or current.

I've had my OD light flash and no codes. Turned out to be a bad harness connection where it comes into the engine bay and goes up into the cab. At 180, you may have hit the temp warning.

 

You would need an oscilloscope to check it. It uses a flying magnet pickup and sends a signal, not a resistance or current.

I've had my OD light flash and no codes. Turned out to be a bad harness connection where it comes into the engine bay and goes up into the cab. At 180, you may have hit the temp warning.

It's not just the flashing overdrive I'm having hard and erratic shifts. But I still have all the gears

 

Mine did that as well when my harness was out of wack. I disconnected, cleaned, and put in some dielectric grease. That fixed that issue. Then for the overheat, I would shift a bit odd, but had all gears. I have not had an issue since I put in a 6.0 trans cooler, but temps have lowered too, so I'm not certain it is totally fixed.

You could swap out the VSS. Not a fan of swaptronics, but for magnetic pickups, there is not much else to do. You can data log and review the data to see if the VSS signal jumps or skips, but not much else. The E4ODs do have some issues such as the solenoid packs going out. I think intermittent issues with the trans are typically electrical.

 

Mine did that as well when my harness was out of wack. I disconnected, cleaned, and put in some dielectric grease. That fixed that issue. Then for the overheat, I would shift a bit odd, but had all gears. I have not had an issue since I put in a 6.0 trans cooler, but temps have lowered too, so I'm not certain it is totally fixed.

You could swap out the VSS. Not a fan of swaptronics, but for magnetic pickups, there is not much else to do. You can data log and review the data to see if the VSS signal jumps or skips, but not much else. The E4ODs do have some issues such as the solenoid packs going out. I think intermittent issues with the trans are typically electrical.

Thank you this has been really helpful. My speedometer does bounce just a little while driving. Also my shifter is just to the right of the gear letters would that affect anything

 

The pointer at the dash can be adjusted in the steering column. It's just a little screw adjuster. Normal for them to be a bit off over time from the indicator cable stretching over time. What matters is the position switch on the trans. It needs to be adjusted correctly using a special tool. I don't think that would cause an intermittent issue if it was out of adjustment though. They don't need to be adjusted unless removed though.

A bouncing speedo is typically a VSS going out. It can sometimes be the PSOM though, they do fail sometimes.

 

The pointer at the dash can be adjusted in the steering column. It's just a little screw adjuster. Normal for them to be a bit off over time from the indicator cable stretching over time. What matters is the position switch on the trans. It needs to be adjusted correctly using a special tool. I don't think that would cause an intermittent issue if it was out of adjustment though. They don't need to be adjusted unless removed though.

A bouncing speedo is typically a VSS going out. It can sometimes be the PSOM though, they do fail sometimes.

Thank you. I've read alot of forums with mixed info you are really helpful. I think my psom is ok bc the speedometer and odometer do work. I just noticed the speedometer bounces a little more so a 60mph or more

 

You might need to just pull the VSS and clean it. I have read that the VSS is prone to picking up magnetic fines from the differential that degrade the ability of the pickup to sense the tone ring.

 

Thank you for your help I'm actually pulling it off to clean it now

 

Make sure the VSS seating surface and the corresponding Diff surface are clean, and that the sensor totally seats when reinstalling it. Cheers!

 

Thank you so much for the tips brother.

 

A special tool is not needed to adjust the MLPS - just align the marks on the switch with the trans in Neutral, as shown here & described in the caption:

(click this text)


That's step 1. Step 2 is to adjust the shifter cable as described in this caption:

(click this text)


Step 3 is to adjust the shift indicator, also in that caption. But make sure the shifter bushings on top of the column are not worn or loose.

(click this text)

 

A special tool is not needed to adjust the MLPS - just align the marks on the switch with the trans in Neutral, as shown here & described in the caption:

(click this text)


That's step 1. Step 2 is to adjust the shifter cable as described in this caption:

(click this text)


Step 3 is to adjust the shift indicator, also in that caption. But make sure the shifter bushings on top of the column are not worn or loose.

(click this text)

I will check this. But I really dont think this is the cause of my issue. But at this point I'll be checking everything. I'm a DIY kinda guy and this is my first diesel. I've had to learn ALOT in a shirt amount of time

 

Hey all just wanted to update. I believe the vss was the problem. When I pulled the old one it did have metal shavings on it so I believe that could mess with the signal. Since it was pretty cheap I just replaced it instead of cleaning it. I also disconnected the mlps and the solenoid pack connectors and cleaned and greased all the connectors. I had the batteries disconnected while I was messing with the connections so that cleared the od light. So far I've drove it around a bit and it shifts alot better and seems to be normal timing and the od light has not come back on

 

Replacement ABS sensors are spotty at best. I'd clean the original (it only takes a paper towel, or a few blasts of shop air) and keep it in the truck just in case.

But the root problem is the shavings... Were they fine black powder, or shiny sharp flakes?

The only grease that should be used on electrical terminals is XG12 Electrical Grease; never XG3 or any other dielectric grease, or any chassis grease, or antiseize, or...

Amazon.com: Genuine Ford Fluid XG-12 Electrical Grease - 3 oz.: Automotive

Amazon.com: Genuine Ford Fluid XG-12 Electrical Grease - 3 oz.: Automotive

www.amazon.com

Disconnecting the batteries ALSO clears all the adaptions from the EEC/PCM, so the engine behavior will change for at least the first 50 miles. It's better to just clear codes using a decent scantool.

 

You can help narrow down a VSS versus PSOM issue if you have an Edge CTS in your truck. I’ll explain with my situation a while back.

I was have hard shift issues with the O/D light flashing like you. Got to the point it was almost happening daily. I tried cleaning the VSS but it only worked for a day or two. My speedometer and odometer always kept working great but in the end my PSOM was shot. I used my Edge CTS to have one of my digital gauges show vehicle speed. This digital output directly displays the value the PSOM is reporting to the PCM. Using this method, I was able to see my digital speedometer drop to 0 mph and then the O/D light would start flashing and the hard shifts would start. While my digital gauge showed 0 mph, my physical speedometer would be showing normal speed readings. My limited understanding is the PSOM was sending a 0 mph readings to the PCM while the transmission was telling the PCM it is in motion. This causes the PCM to put the transmission into limp mode to protect it until the PSOM begins sending normal values. I sent my PSOM off to get repaired and they let me know a capacitor (or something) was burned out. After the PSOM repair, I have only had this issue return once or twice briefly in the past 7 months. I know this isn’t a perfect fix in my case, but it is much better than before.

I found these videos on YouTube when I was researching this problem. They helped me out. I went through Module Mechanics for the PSOM repair.

PSOM Repair 1992-1997 Ford F150 F250 F350 F450 F550 | Gauge Cluster Repair Service

Is your F Series having any of these issues? Harsh / delayed transmission shifts Rough shifting sending transmission into limp mode Code 452 stored in

www.modulemechanics.com

Sent from my iPhone using Tapatalk