1990 R2500 Suburban speedometer not working

[vista_burb90]

For a while now my speedometer will hold at about 65 when running. Sometimes the needle will fall all the way to the right when off. Sometimes needle will end up at far left and then bounce when running or sometimes just hold at 0 when driving. Kinda odd…
Trip and odometer has no issue tracking mileage.
Cruise control works and shifts great too. Can anybody confirm my thoughts leaning toward a bad gauge?

M40 — TRANSMISSION,AUTOMATIC 3-SPEED(THM400-475/3L80)

Thanks!

 

[HotWheelsBurban]

For a while now my speedometer will hold at about 65 when running. Sometimes the needle will fall all the way to the right when off. Sometimes needle will end up at far left and then bounce when running or sometimes just hold at 0 when driving. Kinda odd…
Trip and odometer has no issue tracking mileage.
Cruise control works and shifts great too. Can anybody confirm my thoughts leaning toward a bad gauge?

M40 — TRANSMISSION,AUTOMATIC 3-SPEED(THM400-475/3L80)

Thanks!

That was my last square body Burb, but I never had that problem with it.... If you could get another gauge cluster and swap the speedometer out, that would confirm your theory....
Back in the day, this type of thing was usually a bad or loose speedometer cable. But these speedometers are electronic and run by the PCM (I think?).

 

[BKING33]

I had the same problem with my speedo. I just recently got it repaired by a repair shop that does gauge restorations.

 

[83Stepper]

Wonder if the speedo isn't getting the signal from the VSS sensor, or an intermittent signal causing it to bounce around like that. But if you can get your hands on another speedo to test the theory of it being a bad speedo, do that first. Probably be cheaper than swapping out the vss sensor since the cruise is working correctly and not being affected by the dropout/peg on it.

 

[Chevy 88]

I would buy a HUD display for the spedo. It projects the speed onto your windshield. That way you can see your speed without taking your eyes off the road. They plug into the cigarette lighter and work off of GPS. Plug and play, and way cooler than the dash gauges. $20.

Amazon.com

 

[gmbellew]

1990, I think, is VSS. but i am not 100% on a 2500. if it is VSS and no codes being thrown and cruise works i would strongly suspect the speedo gauge itself is the problem. because if the VSS were not sending the signal to the ECM, and code would be thrown.

 

[BKING33]

If your odometer is working fine like mine was, your VSS is good. Just need gauge repaired.

 

[quaddriver]

I have this problem as well and am about to get into it now that the new AC is in...

ODO works. when the speedo does work, it works fine. it comes to its senses on long drives on hot days, otherwise, its at 65, sometimes 35 or zero.

The cruise works, and the ECM is telling the scan tool my speed. from what I understand the DRAC decodes the VSS for the ECM and the speedo head. what wire cable runs from it to the head? I will be getting into the dash soon when she comes off the road for winter and while I am in there doing LED dash light upgrades. I had also thot of doing the tach upgrade and moving fuel to down low on the left, but parts are hard to get...

anyone ever get in here? the drac is below the radio?

 

[90Saburban]

I had the same problem with my speedo. I just recently got it repaired by a repair shop that does gauge restorations.

Does that repair shop do mail-in repairs? I suspect my gauge also needs to be repaired.

 

[BKING33]

Pretty sure they do mail in. Lucky for me they are local. It's call Powl's. They are in Lancaster Pa.

 

[Smtty58]

If this is like my '90 Crewcab, the speedometer is cable driven, with the VSS built into the speedometer. There will be a small black socket on the back of the speedo, housing an optical sensor. Although, your symptoms sound like a dry cable. The factory lube dries out or hardens over time, causing erratic action, similar to what you describe.

 

[Gander]

If this is like my '90 Crewcab, the speedometer is cable driven, with the VSS built into the speedometer. There will be a small black socket on the back of the speedo, housing an optical sensor. Although, your symptoms sound like a dry cable. The factory lube dries out or hardens over time, causing erratic action, similar to what you describe.

1989 was the final year for the mechanical speedo with VSS attached in the back. 1990 and 1991 squares had fully electronic speedos. No cable. The 90-91 speedos had 000000.0 odometers rather than 00000.0 like the previous years and they said “quartz” on the bottom of the face.

Here’s a link to someone working on a 1990-1991 squarebody speedo. Watch it and you’ll see what I mean about the differences between 1990-1991 and 1989 and back. I went through all of this and more building the tach cluster do my 1987 with factory parts. I wanted a trip odo but have a mechanical cable so ended up using a 1988-89 I found NOS still in the Delco box. 1988-1989 were still mechanical but had the trip odo. The part number showed correct replacement for 1987-1989 but 1987 didn’t have the trip odo and ai know because my truck is a 1987. Back of the speedo was a bit different though. Had to trim the back of the 1985 tach cluster back to fit either my 1988 Speedo or the 1988-89 replacement I ended up using.

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[YakkoWarner]

Does that mean in the 1990 and 1991 years the VSS was down at the transmission? Or did they still have a cable coming into the cabin attached to the VSS and then have the ECU control the speedo?

 

[gmbellew]

Does that mean in the 1990 and 1991 years the VSS was down at the transmission? Or did they still have a cable coming into the cabin attached to the VSS and then have the ECU control the speedo?

VSS at the transmission or transfer case

 

[Smtty58]

Gander, I watched that video. My speedometer is definitely the old cable style with the 5 digit odometer. I wonder if it was a mid-year change? But the OP has the newer electronic style, so my post doesn't help him.