Speedometer stopped working

[Lt.Del]

I was driving home the yesterday afternoon in my 1991 5.7 L 4x4 sub and I started seeing my speedometer jump around alot.  Then it froze on 15 mph and wont move. A little further, I saw it jump up one more time then went down then went again to 15 mph.  I am puzzled.

the odometer works just fine.  

I unhooked the battery for a few minutes, and then reattached. Started the motor back up and it is still stuck on 15 mph.

What's the deal?  I don't know if it is like the older trucks with a plastic gear on the shaft of the trans or not.  Since the odometer still works, I guess not.  I guess it is some electronic sensor perhaps.  

[VileZambonie]

Your truck has a vehicle speed sensor on the transfer case which sends a signal to the DRAC VSS buffer

Possibilites:

You may have a faulty VSS or driven gear

The DRAC is faulty

The Speedo is bad

Or there is a wiring issue

Do an initial inspection of the vss and wiring.

[Lt.Del]

If the VSS is bad, would the cruise control not work?  Cruise control does work, which is why it puzzles me.  If the cruise works, would that rule out the  DRAC being bad?

There is no speedo cable, right? since it is electronic.

[VileZambonie]

The cruise control module receives it's input from the DRAC (vehicle speed sensor buffer). If the cruise is functioning correctly and the odometer is still clocking I would suggest replacing the speedometer. You can either find a used one or have yours rebuilt.

There is a place in Virgina that rebuilds them called Southern Autotronics. Their info is 330 norfolk st richmond VA 23230
(804) 353-5400 or (800) 572-2880

[Lt.Del]

Wow, thanks for searching that for me Vile.  That is right down the road from me, about 6 miles.
thanks

I did some searching and found these...they are all the same company just down the road....you can send in your speedo guage and they'll fix it for you--they cater to the whole Nation....

www.speedotest.com
www.carRadio.com
www.speedometerGears.com
www.navHQ.com
www.instrumentclusters.com
www.southernElectronics.com

[DnStClr]

The DRAC converts the mechanical speedo cable movement into an electronic signal doesn't it? If the odometer works ( it's got its own little motor in the speedo cluster) I'd suspect the DRAC. Either way, the cluster would have to be pulled. Must be nice to be close to shops..

[Lt.Del]

Yeah, Richmond doesn't have much if you rule out the Civil War stuff, so I feel kind of lucky about the shop that does everything here.

I considered just getting a used speedo to drop in there but the mileage would forever be off. There was one on Ebay that read 220,000 miles. I don't want to drop that in there.  I think it is in the speedo.  The cruise and odometer work in mine, so i think it is the speedo guage. 90 and 91 subs didnt have speedo cables in the back of the guage cluster, it is electronic.  That figures.  I went to the salvage yard (my toy store) and saw a lot of our style trucks in there--even picked up a few extra parts for my 79, but, no 90-91 subs.