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vss, oss, freaky speedo-help!

2103 Views 2 Replies 3 Participants Last post by  jpciron
It's funny how much you learn when your truck develops a problem!!

I have a 2001 F250, 7.3 with some sort of electrical issues! It has a 6" Fabtech lift, 315/75/16 tires, superlift tru speed sensor calibrator, a WD quadpower chip, triple autometer pillar gauges, ais intake with foam fender sleeve mod, ATS tranny and controller, BTS torque converter, and a crazy speedo!

It all started when driving to work one rainy crappy morning. The speedo quit and all hell broke loose........flashing OD light, tranny acting bad, at times it seemed as if the torque converter was locking up and it tried to stall at stop signs. I tried leaving work and had a hard time getting it going.......put it in drive and it just wanted to stall like it was a manual transmission and the clutch was not pushed in. I made it 3/4 of the way home (the rain had stopped and it turned out to be a nice day) and all of a sudden the speedo sprung to life and all was well. All troubles vanished when the speedo worked again. I came home, perused this site and decided to try the VSS and check wires. The new VSS seemed to work until we got another bout of wet rainy weather.

This time the speedo acted up...sometimes worked, sometimes worked but read the wrong speed and only quit intermittently. The truck acted up a little, but not nearly as bad as it did the first time. Although, one morning I tried taking off as I noticed the speedo was bouncing radically, the truck again acted like the torque converter had locked up and just stalled. I left it right there and took my other vehicle that morning and hit this forum again after work.

Next we figured surely the problem must be the OSS! We ordered one (of course mine is odd and had to be ordered from the dealer) and put it on and checked wires, fuses, relays, etc. The speedo (I assume from stalling mid bounce) was pegged over by 100 mph and while starting the truck and taking a test drive after installing the OSS, the needle was just hanging at the bottom and getting pushed by the shift lever indicator pin. The odometer was not working either so we knew it was not just a dangling needle! The truck seemed to shift OK, but I did not dare drive it like that. We again messed with the fuses and messed with the tru speed plug in. For some reason as my husband was moving stuff around, the speedo jumped back off of the bottom but still did not work. Our transmission shop friend happened to come over at that time and looked things over quickly. He said try driving it and if it shifted OK I would not do any damage. I took it around the block a few times and the speedo started working but not correctly-the truck seems to be shifting properly regardless of the crazy speedo.

Today while driving it I noticed the speedo seems to read at least 10mph too high (and the miles rack up too fast when it does this). At times it will bounce back to where I think it should be (as per the tach reading) and then jump back to the too high reading. The cruise works, but of course when the speedo jumps up to 70 it thinks it is going too fast and slows down.

What the hell?! I have read the posts about the alternator-does that sound like something I should look into next, or does it sound like a tru speed issue?

I am also thinking I should invest in my own scan tool (since I get attached to my powerstrokes and keep them forever). I know they are not all created equal-what kind should I get?

Thank you for all the amazing info on this forum-I don't know what we would do without it!!

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Your problem is almost certainly the tru-speed or a wiring problem between the VSS and the PCM. I don't understand how you made the jump to the OSS. It's not related to the speedometer.
1 - 1 of 3 Posts
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