funky speedo

[RCCola]

I just bought a '92 W-250 5speed. After a couple days the speedo/odo went wanky. Sometimes it's fine. Sometimes it's erratic bouncing from 0 to the actual speed. Sometimes it doesn't work at all. I searched several past threads about this and still am not sure how to determine the actual cause of the problem. Here are more details:

Cruise control works, even when the speedo doesn't

I put a drill on the gear drive and the speedo read normally (and steady) (but the speedo also worked briefly when I reassembled and hit the road.

The square drives seem to be solid--I pulled the drive gear from the case and screwed the speedo gear box to it and it felt tight, everything seems to spin freely.

I looked at the driven gear thru the hole for the drive gear (assuming I don't have my names backwards on drive(n) gears) and it is yellow and appears to be in good condition.



Reading the past forums I need to check the yoke nut and try some cleaner/dielectric grease but are there any other definitive tests to isolate the driven gear or the electric speed sensor?



Thanks and Hammerdown!

 

[TMWeber]

I had the problem in my 93. It was the speed sensor. I went to DC, explained the symptoms (exact same as yours) and they gave (sold) me a new speed sensor. I went home and installed it in about 10 min (including finding the tools!). It was very simple and not expensive, around $40(?).

Tim

 

[dpuckett]

BEFORE you spend your money.....

Take apart your truck end pigtail and make sure the connector ends are perfectly round, and that you have a good connection there. If they are out of round, they will make the speedo eratic. I had a problem with the ground side. YOu may have to do alittle soldering to get a good connection if that is an issue. ALSO, check the drive gear (on transmission output shaft); and make sure everything is tight, and in good working order. Take some brake cleaner or similar stuff and clean it all out real well.



The speed sensor is a common failure in these trucks, but it doesnt hurt to eliminate all other possibilities before shelling out $$$ to the st... . ah, um, dealer.



Good luck

Daniel

 

[Forrest Nearing]

happened to my 91... I pulled the gauge cluster and cleaned and bent the pins in the gauge cluster to ensure a good connection. fixed the problem, and it's still working great 165k miles later.



Forrest