Hey guys, my speedo is goin' out. I'm pretty sure its a ground issue cause it works sometimes then it doesn't...its messing my transmission shiftin' up. Any ideas? I'm not too good with wiring issues. Thanks everyone.

 

The first time my speedo went out in my 92, it was the driver card in the speedo head , same thing , it would work then not. The second time it was the tranducer on the side of the trans. The last time it went out it was the driver card in the speedo again. To rebuild the head at a local speedo shop the last time was 700.00. It went out again at 490K so it is still out. I figure if I'm passing people ,I'm going to fast and if there passing me, I'm late..... Mine is a Getrag trans though, I don't know if you can get away with no speedo with a auto...

 

Check the connection of the wires to the VSS mine had a bad connection. I fixed that and it has been fine ever since.

 

Yeah, I try not to pass too many people at this point in time
...moparnut, since you have a 518 as well....did you notice that your transmission would shift depending where the needle fell? I have mainly experienced it goin in & out of OD on the freeway, like the needle will drop under 50 and shift back to third...then it works at times....vss, I'll look it up. Thanks guys.

 

VSS=Vehicle speed sensor...thanks sticky
I'll check it out. Thanks.

 

Two days ago while driving home from work my speedo went dead and the trans dropped out of overdrive like yours is doing.

I did lots of reading on the various forums and narrowed it down to the VSS on the side of the transfer case. I got mine from O Reilly Auto Parts for about 37 dollars.

Fixed it right up.

 

Kayers, thanks man. I checked it yesterday morning, unplugged it and wiggled it and it fixed the speedo for awhile. I'm thinking thats what it is too. I 'll replace that and hopefully the wiring from there up isn't bad. Thanks guys.

 

OK...new VSS, worked for a day....starting to go out again. Had some crusty wires, had that fixed, still not working....what do you guys think....bad ground?

 

Your problem wont affect any shifts except the shift into overdrive. 1-2-3 are hydraulic (valve body) controlled.

 

Well, the fact that it shifts back into 3rd when I'm going 65-70 on the freeway cause my needle bounces under 45 really sucks. Plus I want to FIX it...I think its a bad ground.

 

well if it's kicking out of overdrive, then you are on the right track.

 

So what was it?

Thanks!

-Shiny

 

This may or may not be of help............I changed the O ring on the fuel heater just above the fuel filter , in doing so I disconnected the plug with the two heavy gauge blue wires that snapped into the fuel heater. When the job was done I reconnected everything and took the truck for a test ride. I noticed that my speedometer had stopped working. I crawled underneath and saw that two of the wires coming out of the 727 were also heavy gauge blue wires. I went back to the fuel heater connection , disconnected and cleaned and dried the connection as best I could and on my next test run , my speedometer was working. Now I find it odd that these wires would be somehow interconnected so this could be just coincidence. Thought I would pass this on and maybe some of the electrical guys could comment.

 

Yo shiny....bad wiring mainly... I put a couple of VSS's on and would fix it for a day but not completely, ....got it fixed now, trucks running great! I think the wiring was my greatest issue in so many of the problems I have had, ran some new wire and haven't had an issue since.

 

P.S. I got this rig from a farmer, so it wasn't just one wire, and its also had bad grounds. Me, my buddies Valley Auto and Big Twin here in Idaho have all helped to cleaning this problem up, problem meaning O/D going out, no heat, windows going out, etc.etc...finally speedo. So over a year, I think I finally got it all cleaned up to a manageable issue....oh, and rebuliding the tranny helped a ton as well.......I am praying it stays fixed for awhile cause my sweet wife cut me off from adding anything else on till next year