Question about the speedometers used in our trucks

[Darkrider]

Ok this is a random a** question i know. But as far as i understand the set up in our trucks it is the VSS that determines what our speedometers read correct?

 

[great white]

Well, yes and no.

The VSS generates the pulse from the output shaft of either the transmission (2x4) or the transfer case (4x4).

Depending on the year, the cluster/DRAC/VSSB/PCM delivers the signal to the speedometer....

 

[Darkrider]

Well, yes and no.

The VSS generates the pulse from the output shaft of either the transmission (2x4) or the transfer case (4x4).

Depending on the year, the cluster/DRAC/VSSB/PCM delivers the signal to the speedometer....

Ok the trucks in question are my 1989 K3500 and Eric S.T.s 1990 C1500, I am getting the cluster from Erics truck to use in mine. Of course the tire sizes will be far different given mines a 4wd.

 

[88GMCtruck]

88-91 clusters use an internal DRAC (digital ratio adapter controller). the DRAC convert the pulses to the proper signal for the cluster, RWAL, cruise, etc. It's where the tire/gear is "programmed". I've never done this, but here are instruction on changing the ratio for a 88-91 cluster.

http://www.454ss.com/Articles_new/tweek/DASHB.asp

Now, if you convert to a 92-94 cluster, they had an external DRAC module and you can install DIP switches in place of the jumpers to make an infinitely adjustable module.

http://614streets.com/drac.html

 

[Darkrider]

88-91 clusters use an internal DRAC (digital ratio adapter controller). the DRAC convert the pulses to the proper signal for the cluster, RWAL, cruise, etc. It's where the tire/gear is "programmed". I've never done this, but here are instruction on changing the ratio for a 88-91 cluster.

http://www.454ss.com/Articles_new/tweek/DASHB.asp

Now, if you convert to a 92-94 cluster, they had an external DRAC module and you can install DIP switches in place of the jumpers to make an infinitely adjustable module.

http://614streets.com/drac.html

Thanks for the links Dave!

Sent from my SGH-I547C using Tapatalk 2