91 gauge cluster crossover extension cable for moonie conversion?

Chadryan44 · Jun 2, 2020

Hi there,
Lurker here with a first time post. Your threads have been super helpful while bringing my 91 Chevrolet C1500 5.7L back to life.

I currently have the moonie gauges and I've sourced one of the elusive 91 Needle gauge clusters. I've read countless threads on the pinout changes needed and the cutting of the dash. Has anyone considered making an extension cable to jump between the existing gauge cluster connector and the replacement gauges? It would make the required adjustments on the pinout and also bring in the pin for the tach.

I was going to try this myself after a trip to the local junkyard to hack the needed spare connector. What do you think? Really hoping someone has done this already! It would be sweet if such a patch cable already exists.

someotherguy · Jun 2, 2020

No cutting of the dash needed. The 91 needle cluster has the same housing design and connector style as the 88-91 moonies. Electrically and physically, swapping 91 moonies for 91 needles is a drop-in. IF your truck was an 88-90 then there are the three wires that need to get moved around in the connector and there are threads regarding those.

After that all you need to concern youself with is proper speedometer calibration for your axle ratio and tire height. If you haven't found my thread on replacing the micro-fuses with a DIP switch, it's here -> https://www.chevytalk.org/fusionbb/showtopic.php?tid/258562

The dash cutting, connector swapping, etc. is for using 92-94 gauges in an 88-91. The housing and connector are different, and the 92-94 clusters use an external module for converting the speed sensor signal (DRAC module.)

Richard

DerekTheGreat · Jun 4, 2020

Since the trucks I did the swap to were pre '91 I ended up having to move wires around. To make that easier, I trimmed away a bit of the dash behind the cluster so I could have better access to the wiring harness. I didn't like having to do that, but I'm over it now.

johnnydrama · Jun 15, 2020

Hi

someotherguy said:
No cutting of the dash needed. The 91 needle cluster has the same housing design and connector style as the 88-91 moonies. Electrically and physically, swapping 91 moonies for 91 needles is a drop-in. IF your truck was an 88-90 then there are the three wires that need to get moved around in the connector and there are threads regarding those.

After that all you need to concern youself with is proper speedometer calibration for your axle ratio and tire height. If you haven't found my thread on replacing the micro-fuses with a DIP switch, it's here -> https://www.chevytalk.org/fusionbb/showtopic.php?tid/258562

The dash cutting, connector swapping, etc. is for using 92-94 gauges in an 88-91. The housing and connector are different, and the 92-94 clusters use an external module for converting the speed sensor signal (DRAC module.)

Richard

Hi Richard. Thank you for all the help that you have been giving people since the old fullsizechevy days.

I hope you are doing well and I hope that you can help me here. I have a '90 GMC Sierra RCSS with moonies. I also have a '91 tach cluster. I know you have shown us before the three wires that need to be changed but the photos are gone. Is there any way you could put those photos back up?

Thanks in advance!

You must be registered for see images

BTW, here's mine.

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someotherguy · Jun 15, 2020

johnnydrama said:
Hi

Hi Richard. Thank you for all the help that you have been giving people since the old fullsizechevy days.

I hope you are doing well and I hope that you can help me here. I have a '90 GMC Sierra RCSS with moonies. I also have a '91 tach cluster. I know you have shown us before the three wires that need to be changed but the photos are gone. Is there any way you could put those photos back up?

Thanks in advance!
You must be registered for see images
BTW, here's mine.

You must be registered for see images attach

Truck's looking good! I'll have to do some searching to come up with that wiring info; it's not something I had figured out, just read where someone else had done it and I've re-shared the info from time to time over the years. When I find it I'll post back here.

Ahh, here we go; apparently I had originally found it on the 454SS forums which seems to still be around.. Anyway the info is brief and you'll need to look up a simple diagram for the cluster connector, then "Move B15 to B11, Move A10 to A9, move A11 to A10." That's for putting a '91 cluster into a '90 (same as 88-89)

Richard

johnnydrama · Jun 16, 2020

Thank you, Richard!

someotherguy · Jun 16, 2020

johnnydrama said:
Thank you, Richard!

No sweat.. I hope it helps. As I said I haven't done that particular swap, but I also haven't seen anyone dispute that info anywhere it's been posted so it *should* be good. Man, if you have a '91 needle cluster that's more than half the battle; hell of a lot easier than hacking in a 92-94 cluster.

Have you seen my write-up on modding the 88-91 clusters with a DIP switch similar to the DRAC modification for 92-95? Super easy.. https://www.chevytalk.org/fusionbb/showtopic.php?tid/258562

Richard

johnnydrama · Jun 16, 2020

Thanks, again! I'm afraid that's a bit too ambitious for me. I'm not a stickler for an accurate speedometer. I just go with the flow of traffic.

johnnydrama · Jun 23, 2020

Hey, Richard, if you're still around, how do I wire the tach? (on both ends!)

someotherguy · Jun 23, 2020

johnnydrama said:
Hey, Richard, if you're still around, how do I wire the tach? (on both ends!)

Haven't had to do one myself but I believe I've read others have found the tach was already wired. Have you tried just hooking the cluster up (after the wire moves already mentioned) ?

Tach signal can be found on the white wire coming off the coil that has its own spare terminal just hanging there, but that would be a hack - that's a diagnostic test point, not the official harness wire for the signal. I'd have to look up where it goes on the cluster connector end.

Richard

91 gauge cluster crossover extension cable for moonie conversion?

Chadryan44

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