Speedo issues

[pulltilbroke]

Well I've been having some speedo issues lately. Last Sept I got the speedo working again with a new used reducer box but it always had a slight bounce to it and got progressivly worse until it just up and quit on me. The other day I'm cruising down the road to go tune a buddys truck and I hit a bump and it starts working agan and is dead nuts steady until I hit another bump and it quits again, hit bump back to operational. I have my Grid heaters disconnected so the WTS light is always flashing at me and I was having issues with it not flashing when the speedo gave up the ghost. So is the WTS light tied in with the speedo somehow? I have checked the grounds and connections and also have another VSS to try. What else could it be?

[BC.livewire]

he wiring inbetween all the parts

I'm to the point are I will be rewiring the hole truck --- man dodge wiring realy sucks

[pulltilbroke]

Anyone else???

[Richie O]

My 92's speedo works every 3rd day. If it works when I first start the truck it will work fine for the whole trip. It either works great or not at all. It never starts or stops working while driving. When it stops I shake everything and check plugs ect. Nothing I do makes it work again. Then a couple days later it kicks in again. When it totally friggs I might do some more looking, maybe not.

[BC.livewire]

those GPS things are cheep than fixing the stock speedo

just my $0.02

[pulltilbroke]

I might throw a VSS at it and see what happens.

I've checked everything I can think of.

[IowaCummins]

could it be a connection problem on the ecm or the main wireing harness going into the cab? i would atleast pull those two plugs and use soem emery clothe and clean the contact points a bit ya know. is it the same plug on the back side of the engine have the vss signal wires in it too? like the one with engine sensors does it also have the vss signal wire in it? if so could have a small wire fraying and causing mixed signals?

[hp383]

wit till its starts showing speed while sitting still in park.... Mine does that most days. Then one day it just started working great, no bounce. Well now its started bouncing again, and has completely stopped working. When it stops working, I can NOT get into OD with the auto.

If there is a good known fix please let me know, a CTD with no OD is worthless

[pulltilbroke]

Sometimes mine will start showing speed at idle and it will climb with engne rpms.

[diesel freak01]

hoenstly that sounds to me like a ground issue, i have no idea where or how to fix but thats what it sounds like to me. maybe try to find a dash ground and clean or look for broken wires (i know ya RIIIIGGGHHHT)

[hp383]

Sometimes mine will start showing speed at idle and it will climb with engne rpms.

Sort of like the speedo thinks its a tach?

Mine does that sometimes also.

Well, yesterday Vinny helped me splice into the ground feed for the VSS, And that didnt make a difference.

I know it has a good ground now, the ground wire is only 16" long, and bolted directly to the frame of the truck, right at the transfer case.

Could this issue be a PCM failure? Lord I hope not!!

[hp383]

Well, I drove all over creation yesterday, and for the past few days, no issues. (Other than the erratic speedo tach thing)

Today i have no overdrive whatsoever. I disconnected the potentioner and plugged in the TPS, got erratic OD. Then unplugged the TPS and hooked the potentiometer back up. Same erratic OD. I tried turning the pot all the way up/down, sideways, etc. I could not get the OD to engage and stay engaged.

I took it to the dealer.(I know, I know) they took all of 3 minutes to just say, its the VSS. The VSS was changed by vinny not that long ago. Do these VSS's have a habit of burning out?

Should I be able to crank the potentiometer up and engage OD at any speed, or even just lock it in?

Is there a way to force the overdrive into gear and just control it via button? This is my only form of transportation, I am somewhat disabled and cant just go rent a car, Cant get in and out.

If anyone is in or close to CB and wants to take a peek please do

[hp383]

Stopped in the turn lane at idle and slight acceleration when light turned green.
Speedo all over the place.

Click to see correctly

[BC.livewire]

I know I could be more helpfull if I was to that point of fixing my truck

but I'm starting with the KDP and a bad liftpump

in a month or 2 I will be more helpfull

[hp383]

Well I got it fixed yesterday afternoon. It was a bad VSS,

The VSS had just been replaced within the last 6 months or so, and it really never helped much. But for some reason the NAPA VSS was just not reading right, but an old 200K Mopar one is reading great.

I also got a message from a member here after mine was fixed, he had an issue with the VSS shaft rounding off. Funny thing is before I read that message, I was looking over the damn near new VSS and noticed the shaft looked like the corners were chamfered. I thought to myself "I wonder if that is part of the problem, somehow the aftermarket part gets shaved or turned down?".

Well it seems that is a problem. Maybe the aftermarket China stuff is not hardened correctly?

Im just wondering now if my VSS shaft is worn, how bad is the socket end on the gear ratio reducer?

As of now my speedo is rock steady, no wiggle, full use of OD. Im Happy and owe a big thanks to Mark Nixon for driving up here, troubleshooting, and installing the parts free of charge. He wouldn't take my money for parts or fuel.