Making a 454SS gauge cluster

[Lordkay972]

Okay, I'm a little under informed, but here's my idea. I read somewhere that its possible to calibrate the speedometer for different wheel sizes. Couldn't you get a custom face made for a normal cluster w/ tach that goes to 110, then recalibrate the speedometer for the new face? The normal clusters are a lot easier to find than 454 clusters, and a lot less expensive too.

 

[88GMCtruck]

Yes, you could if you had a modified DRAC module. They 110MPH clusters read differently than a regular one, and I had to set mine with a GPS and flicking the switches on the DRAC while driving.

Also, the 454SS cluster has a 6k tach.

 

[Lordkay972]

Yes, you could if you had a modified DRAC module. They 110MPH clusters read differently than a regular one, and I had to set mine with a GPS and flicking the switches on the DRAC while driving.

Also, the 454SS cluster has a 6k tach.

Would it be possible to recalibrate the tach on a normal cluster? Would it even be necessary though?

 

[88GMCtruck]

Not necessary unless you wanted it to look like an actual 454SS dash. I have no idea how to re-calibrate one either.

 

[someotherguy]

I could certainly see recalibrating the DRAC in a way that the input ratio is less so that you work out to reasonably accurate speeds across a 110 MPH range instead of 85 MPH; the overall physical sweep of the stepper motor looks about the same. Just gonna take some math skills, or a LOT of trial-and-error comparing against GPS.

I don't see you recalibrating the tachometer though without some really good understanding of electronics. A well-placed resistor of the correct value is all it is likely going to take, but figuring that one out will take someone that knows circuits better than most of us do.

Then you need to make an appropriate gauge face with the new 110MPH range and the 6K tach. And have it be on a material that will transfer the light through the correct places, and block it in the others, and distribute the light evenly through the lettering/numbering so that it looks good.

In the end you could probably have found and paid for a dozen 454SS clusters and been money ahead. IMO.

Richard

 

[Lordkay972]

I could certainly see recalibrating the DRAC in a way that the input ratio is less so that you work out to reasonably accurate speeds across a 110 MPH range instead of 85 MPH; the overall physical sweep of the stepper motor looks about the same. Just gonna take some math skills, or a LOT of trial-and-error comparing against GPS.

I don't see you recalibrating the tachometer though without some really good understanding of electronics. A well-placed resistor of the correct value is all it is likely going to take, but figuring that one out will take someone that knows circuits better than most of us do.

Then you need to make an appropriate gauge face with the new 110MPH range and the 6K tach. And have it be on a material that will transfer the light through the correct places, and block it in the others, and distribute the light evenly through the lettering/numbering so that it looks good.

In the end you could probably have found and paid for a dozen 454SS clusters and been money ahead. IMO.

Richard

I know of a company that makes white gauge faces and sells them on eBay. Pretty good quality too. I'm sure if I asked, they could make a 110 one for a little extra. How does a DRAC work?

 

[someotherguy]

DRAC takes the speed sensor input and turns it into the signal the speedometer wants. Adjustment of the DRAC is done by the factory using hardwire jumpers soldered in as a permanently set bank of switches; this affects the math the circuit does to kick out the signal for the correct speedo reading. Changing these jumpers changes the math and resulting signal. This is done based on tire height, axle ratio, number of pulses per mile the particular design of speed sensor produces, etc. Charts out there with all the normal settings and you just replace the hardwire jumpers with a DIP switch (or two, depending on DRAC design.)

http://www.tbichips.com/drac/

Richard

 

[Lordkay972]

DRAC takes the speed sensor input and turns it into the signal the speedometer wants. Adjustment of the DRAC is done by the factory using hardwire jumpers soldered in as a permanently set bank of switches; this affects the math the circuit does to kick out the signal for the correct speedo reading. Changing these jumpers changes the math and resulting signal. This is done based on tire height, axle ratio, number of pulses per mile the particular design of speed sensor produces, etc. Charts out there with all the normal settings and you just replace the hardwire jumpers with a DIP switch (or two, depending on DRAC design.)

http://www.tbichips.com/drac/

Richard

I'll see if I can get a custom face made, then I'll start the trail and error with the DRAC. Will post correct orders once I figure them out. Although, wouldn't they be different for almost every truck?

 

[someotherguy]

Unless the person has the same height tires and same axle ratio as what you work out for yours, yes, the settings would be different. Also, DRAC setup for GMT400's is only used in 1992-1995 models; 1988-1991 have a different design built into the cluster itself and the settings aren't the same. Kind of doesn't matter since 1988-1991 are moonies anyway so the gauge face wouldn't help them, even the less-common 1991's with the needle gauges I believe are slightly physically different in layout vs. 1992-1994 though it's been a while since I had one of those in my hands.

And of course 1995 has a totally different cluster anyway and those people can just pop a 120MPH Denali/Escalade cluster in.

Richard

 

[ccreddell]

The idea that Skylark and I have been thinking about is to use a Canadian speedo which goes to 140 and play with the DRAC until it reads MPH instead of Km. Might have to play with the resisters inside too. That would give you a 140MPH speedo, with no overlay. For the 95-98 trucks you'd have 180MPH speedo. But those have to be reprogrammed in the computer.