Hey gents, My speedometer isn't working, I've checked the gauge, cable and I replaced the speed sensor in the transfer case. I also checked all of the related fuses to no avail. My ODO doesn't work either, so I'm starting to think its something electrical. Anyone have any ideas? Ill pretty much try anything now, I need it fixed so I don't end up getting a speeding ticket.

 

I ran a jumper wire to mine from another fuse it works fine. Test to see if you have power to your speedo fuse

 

I'm pretty sure the 87-91 speedo is cable driven only, so this shouldn't be an electrical issue. The speed sensor is only for information for ABS and the PCM.

If all the speedo cables are good, I'd say check the speedo unit.

 

It is cable driven, I just didn't know if there was some electrical component to it. I checked the unit and when I spin the cable with my fingers the needle goes up so I don't know what else to try. And I changed the thing the cable goes into on the transfer case. There is two wires coming from that, I didn't know if that was part of the speedo

 

You're correct about the transfer case sensor, that's the speed sensor for ABS etc. There's a plastic gear on the end that goes into the transfer case, correct? Only asking because replacements don't normally come with a gear, you have to swap your old one over.

I'm not familiar with the speedo cables on this model. Is it one long cable, or multiple cables that connect to each other? If it's multiple cables, did you spin the cable from the transfer case end? Trying to rule out, if it is multiple cables, that maybe one cable isn't working correctly.

I'd also try (if you haven't already) to remove the speed sensor, leaving the speedo cable attached, and spin the speed sensor gear and check operation of the speedo. If the speedo works when doing this, your problem will most likely be in the transfer case, or whatever drives the speed sensor.

 

I didn't see a gear on either of the sensors. I thought the sensor for the ABS was on the diff? And it's the single long cable.

 

My bad, I was thinking of the VSS in my SHO, which I just finished replacing. Looks like your VSS has a speedo cable tip on the end of it that gets driven. Same theory though, if you spin it from the end of the VSS and the speedo works, I'd assume it's a problem with whatever drives the VSS in the transfer case.

You're correct about the ABS sensor also. Your VSS only feeds info to the PCM.

Perhaps I should have another cup of coffee?

 

Haha coffee sounds good. So how should I check the gears in the transfer case?

 

I don't have any first hand experience with that, because my 95 is an electronic speedo, no cable.

However, if you put the rear on jackstands, remove the speedo cable from the VSS, and put the truck in drive, you should be able to see the end of the VSS where the cable goes in spinning.

 

Alight I'll try that tomorrow

 

When you replaced the speed sensor, did you swap over the speedo gear? If so, check that gear to see if it is stripped. If it is OK, then the drive gear inside the xfer case is bad.

If the cable moved the speedo when you turned it without the cable hooked to the speed sensor, check the end of the speedo cable to make sure it is a square shape end. I had a few round off and caused no speedo/odo movement.

Also now is a good time to relube the speedo cable, that old dried up grease does cause problems with the cables snapping or round off the square end.

 

I fixed them! I decided to go out and check the ends like Eddie said and got to messing around with it. I ended up taking the gauge apart and checking the back of the gauge and what do you know the cable wasn't in all the way. I ran it up and down the road to make sure, its a little twitchy but its better than not having one at all

 

Awesome! If you lube up the cable, maybe it'll smooth out a bit.

 

How should I go about doing that?

 

In my SHO, I disconnected the speedo cable, and shot some graphite lock lubricant spray in from both ends. Pretty sure I got the graphite from Ace Hardware.