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Loves OBS Trucks
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Well the Tranny was around 180 last night. Cel set off and the overdrivelight started flashing. Shifted hard from the line pressure increase. Hooked up the snap on scanner and there are no codes. I wonder if its from the ATS torque convertor controller in conjunction with the exhaust brake. Why would there be no codes?
 

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Loves OBS Trucks
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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.
 

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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?
 

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Loves OBS Trucks
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Discussion Starter #6
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.
 

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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?
 

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Harl
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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
 

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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.
 

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

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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.
 

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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
 

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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.
 

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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
 

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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.
 

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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.
 

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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
 

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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
 
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