VSS Speedo Problem

[pvkj454]

I used a 89 Suburban gauge cluster with the electronic speedo and the transfer case is a NP241 from a Blazer that has the 2 wire VSS sensor for my build. http://67-72chevytrucks.com/vboard/s...d.php?t=404146

I connected the purple wire of the VSS sensor to the speedo input on the cluster and the other to the cluster ground. The speedo will peg out at over 85 mph when the truck is moving and drop back to zero when stopped. I tried swapping the wires at the VSS sensor and it made no difference.

Any ideas? Thanks.

[68 TT]

Originally Posted by pvkj454

I used a 89 Suburban gauge cluster with the electronic speedo and the transfer case is a NP241 from a Blazer that has the 2 wire VSS sensor for my build. http://67-72chevytrucks.com/vboard/s...d.php?t=404146

I connected the purple wire of the VSS sensor to the speedo input on the cluster and the other to the cluster ground. The speedo will peg out at over 85 mph when the truck is moving and drop back to zero when stopped. I tried swapping the wires at the VSS sensor and it made no difference.

Any ideas? Thanks.

I could be wrong and don't have the electric speedo wiring diagram handy but I thought the input for the electric speedo came from the ECM and the VSS output from the trans went into the ECM, not directly to the speedo.

[c10sport]

It goes to the ECM and then through a DRAC module if i remember right.

[Big Port Jimmy 6]

This should fix the problem.
http://www.dakotadigital.com/index.c...rod/prd126.htm


jay

[joe231]

for what it's worth, '89 burbs still had a manual speedo. The electronic speedo is from 90-91 burbs.

[pvkj454]

Thanks for the help. I was hoping the ECM only read the signal and did not change it. I am not using the ECM.

I will order the interface box.

Thanks,
PK

[68 TT]

Originally Posted by pvkj454

Thanks for the help. I was hoping the ECM only read the signal and did not change it. I am not using the ECM.

I will order the interface box.

Thanks,
PK

Is this a mechanical speedo with a cable to drive it or is it electronically driven?

The way you phrased the question I assumed it was electronic.

Didn't you state that the NP241 and speedo came out of the same Blazer?

[pvkj454]

Originally Posted by 68 TT

Is this a mechanical speedo with a cable to drive it or is it electronically driven?

The way you phrased the question I assumed it was electronic.

Didn't you state that the NP241 and speedo came out of the same Blazer?

It is electronic. I went back and looked at the eBay listing. the cluster is 90-91 EFI Suburban 1500.

The transfer case came out of a EFI Blazer.

[68 TT]

Originally Posted by pvkj454

It is electronic. I went back and looked at the eBay listing. the cluster is 90-91 EFI Suburban 1500.

The transfer case came out of a EFI Blazer.

The early TBI rigs used a cable driven speedo with an optical VSS unit mounted to the back of the speedo head. If your Blazer transfer case has a VSS output it is the later style that came with an electronic speeometer. From what you are saying you have the later style with a VSS.

You will either need an ECM & DRAC to run the speedo you have with the NP241 you have or you can simplify things and switch to a cable speedo output transfer case and cable driven speedo cluster.

The electronic cluster is worth far more than the cable driven one so you should be able to sell it to a guy doing an LS swap pretty easily and cover the cost of getting another cluster.

Not sure you can swap out the VSS parts on your NP241C for cable driven speedo parts from an NP208 but it might be possible. I know they share some internal parts. A little research will be needed here unless you just want to find another transfer case entirely.