VSI Vehicle Speed Indicator connecting wire

[wjpatton]

Just had my '90 D250 727 trans rebuilt and the tech was nice enough to point out the poor condition of the insulation on the wire going to the VSI. After getting home I crawled under and had a look at just how much of the insulation was missing. Wow, it is amazing I had not had a problem with the speedometer not working! Before I start chasing the other end of this wire, where does it end? And is there a quick disconnect connector or will I have to splice into the existing wire? Thanks in advance guys.

 

[wjpatton]

UPDATE: Was able to remove this entire harness and fabricate a new one from end to end. Wrapped and insulated much better than new, should last a LONG time.

 

[JHylton]

Would the VSI cause the speedometer to display incorrect speed? My '91 has recently started showing speed anywhere from 30 - 50 or 60 mph faster than what it is actually doing. When I first take my foot off the brake, not even applying throttle, the speedometer needle sits there and quivers. Saturday when I started it up to drive it, as soon as I put it in gear, the speedometer jumped to 100.

 

[wjpatton]

I sure think it could! The whole thing is electric, so any spurious electrical signal can cause strange things to happen. I had noticed a couple of times some strange readings before I rewired mine. Replace whichever is easier (aka CHEAPER) for you first: the wiring harness or the VSI unit. In my case, I had enough 18 and 22 gauge wire in appropriate colors to re-do the entire harness from the firewall to the VSI and the neutral safety switch, so that was the first thing. Plus, I knew I had bad wires going to the VSI. I'm sure other guys have some inputs for your problem as well. I have no experience with the actual speedometer. Good luck, and thanks for your service.

 

[RWherley]

Yes, a bad VSI will do that, I have had 2 of them go bad and when they do the speedo always goes crazy

 

[JHylton]

Are they (VSI) a dealer item, or are they available in aftermarket form ?

 

[wjpatton]

You can find them online or through your local parts store (NAPA, AutoZone, etc...)

 

[RWherley]

NAPA part #vss100 stay away from advanced auto and auto zone. they are some kind of stupid universal deal the napa one is just like the dodge one

 

[Don in Missouri]

Where can I find a replacement for the adapter that goes between the speed sensor and the transfer case? Mine is broken. I have 3.54 gears.

 

[RWherley]

From the dealer, I got one a few months ago ill see if I can find the part number but if not the dealer can look it up using your trans, gears, and tire size.

 

[Don in Missouri]

I'd appreciate the help. They told me it was not available.

 

[RWherley]

They are lazy and don't feel like looking it up, I got a part #0442 8549-001 its for a 5 speed 4x4 with 3.54 gears and 33 inch tires.

 

[Don in Missouri]

Thanks much!

 

[JHylton]

Well I changed the VSI and problem still exists. Next step is to inspect and/or replace wiring back to firewall. Wiring looks good down on the transmission end, however that doesn't preclude it being bad further up the wire !!

 

[wjpatton]

Well I changed the VSI and problem still exists. Next step is to inspect and/or replace wiring back to firewall. Wiring looks good down on the transmission end, however that doesn't preclude it being bad further up the wire !!

When I replaced mine, I checked the wire, and it was totally shot in several places. Ended up making an entirely new wire, all the way to the firewall. Not too tough, and everything works!!!!