[PDC]

Looking at swapping the gauge cluster in my 73 Trans Am. It currently has functional 6k tach and 100 mph speedo which clearly is not correct for the 73 car. But every gauge in the cluster works: tach, speedo, temp and oil pressure.

I have done quite a bit of research and see that the contacts on the printed circuit boards ‘appear’ to be consistent for 1970, and then 1974-76 cars. The circuit board contact pattern for 1971, 72, and 73 cars is all the same - but it is different than the 70, 74-76.

My question is this - will the harmonica in the dash harness for a 73 Trans Am work with any 70-76 gauge cluster, or if I have (for example) a 74 gauge cluster, will I need an entirely different dash harness with different harmonica clip?

Because all of the gauges in this technically incorrect 100 mph 6k tach cluster work properly in my 73 car, I wonder if the dash harness clip will power up pretty much any 2nd gen cluster, or if the PO necessarily changed out the dash harness when swapping in this incorrect cluster.

Hope this question makes sense.

Thank you.

[78w72]

Originally Posted by PDC

Looking at swapping the gauge cluster in my 73 Trans Am. It currently has functional 6k tach and 100 mph speedo which clearly is not correct for the 73 car. But every gauge in the cluster works: tach, speedo, temp and oil pressure.

I have done quite a bit of research and see that the contacts on the printed circuit boards ‘appear’ to be consistent for 1970, and then 1974-76 cars. The circuit board contact pattern for 1971, 72, and 73 cars is all the same - but it is different than the 70, 74-76.

My question is this - will the harmonica in the dash harness for a 73 Trans Am work with any 70-76 gauge cluster, or if I have (for example) a 74 gauge cluster, will I need an entirely different dash harness with different harmonica clip?

Because all of the gauges in this technically incorrect 100 mph 6k tach cluster work properly in my 73 car, I wonder if the dash harness clip will power up pretty much any 2nd gen cluster, or if the PO necessarily changed out the dash harness when swapping in this incorrect cluster.

Hope this question makes sense.

Thank you.

posted this on the other thread too:

if the prev owner didnt swap the wire harness & cluster to a later style 6k/100mph with the bigger harmonica connector, then chances are they just swapped the tach & speedo by themselves into the 73 gauge cluster using the smaller connector. but you will need to pull the gauge or look up behind it to verify what connector/cluster it has.

to answer your question, if the 73 has the earlier smaller connector it wont work for the later 74+ gauges as they use the bigger connector. on my base model 72 firebird i swapped in a 74 wire harness & gauge cluster since it uses the same block at the firewall it was easy to swap, that might be an option on your 73 if you plan to swap the harness & cluster.

however, the easier way to do this if the car still has the smaller connector/harness & cluster, is to just swap out the 6k/100mph for a 8k/160mph since the speedo & tach are controlled independently of the printed circuit/harmonica connector. tach is controlled by a standalone wire & speedo is obviously ran by the cable. the only thing that might not work right is the brake or bright indicator in the speedo since they are fed by the printed circuit bulbs.

once the cluster is pulled, the speedo & tach are easy to swap with just a few bolts/nuts on the back side. they repro both gauges new or can find them used for much cheaper. i have a bunch of 8k & 160 gauges if you need them.

[SD455DJ]

There are physical differences in the housings. The 70-early thru 72 had 12-pin harness connection slots while the late-'72 up had a 16-pin slot. Also, the clock adjustment knob is black on 70-71, chrome on 72-up...I believe. Your 73 dash harness should have the 16 pin connector (harmonica) and would work with any late '72-up gauge/tach cluster housing.

Dennis

[PDC]

Originally Posted by SD455DJ

There are physical differences in the housings. The 70-early thru 72 had 12-pin harness connection slots while the late-'72 up had a 16-pin slot. Also, the clock adjustment knob is black on 70-71, chrome on 72-up...I believe. Your 73 dash harness should have the 16 pin connector (harmonica) and would work with any late '72-up gauge/tach cluster housing.

Dennis

Thank You! These pictures are gold to me. I had found images of reproduction contact films on line and had downloaded them for comparison, but with different image sizes and resolutions, it wasn’t nearly as helpful as this.

So if I’ve got a 16 pin harness and connector, I can use a 72-76 gauge cluster?

I’m betting more than one person on this forum knows when GM went from a 160 speedo to a lower top number - are 74 speedos still 160?

Thank you again for this reply - this is all making more sense to me now.

[SD455DJ]

Yes, you can use any gauge cluster/tach housing from late '72 on up. I believe 100 mph speedo's came in '75. The '74 speedo was still 160 mph.

Glad to help...I just went through this as I'm putting a used '70 gauges/tach cluster in my '70 Formula that came without them. We're going the the process of swapping out the original non-gauge dash harness for one with gauges. I'm chronicling the swap in the 70-73 Firebird & TA Tech forum now in the thread "1970 Formula".

Dennis

[78w72]

perfect pics to show the difference in connectors. my 72 is an early build date so it had the 12 pin connector, i swapped harness & cluster from a 74 & all worked out.

PDC, your 73 will have a 16 pin connector for sure & thats why the later 6k & 160 fit right in there. will PM you later about the 8k/160mph clusters i have, they are all later 16 pin.

[unruhjonny]

Originally Posted by 78w72

perfect pics to show the difference in connectors. my 72 is an early build date so it had the 12 pin connector, i swapped harness & cluster from a 74 & all worked out.

PDC, your 73 will have a 16 pin connector for sure & thats why the later 6k & 160 fit right in there. will PM you later about the 8k/160mph clusters i have, they are all later 16 pin.

this post nailed it.
it's plug and play.

[78w72]

* correction to my post, meant to say thats why the the 6k & 100mph speedo fit, not 160.

[PDC]

Originally Posted by 78w72

* correction to my post, meant to say thats why the the 6k & 100mph speedo fit, not 160.

No worries - that’s what I had concluded as well. Eager to see whatever gauge cluster(s) you are willing to part with. My dash bezel is at Randy Comb’s place now getting freshened up and I just ordered some LED 194 and 1895 bulbs for the cluster.

[PDC]

So, I have swapped the gauge cluster in a previous 2nd Gen TA, but that was during the course of a complete dash replacement, so the steering column was necessarily dropped to get the dash out.

Is dropping the column necessary to get the center cluster out? Or does it just provide more room? Wondering if the cluster can be removed with the column in place or if dropping the column is necessary.

Thank you.

[unruhjonny]

my recollection is that dropping it even a little bit, just gives extra room to wiggle out the cluster;
In theory you should be able to pull it straight out, but the lip from the vinyl (dash wrapping) creates a "step" that the cluster hangs up on.

I believe I would back one nut off about a half inch, then back the second nut off till the column was resting on the first (loosened) nut.

[PDC]

Originally Posted by unruhjonny

my recollection is that dropping it even a little bit, just gives extra room to wiggle out the cluster;
In theory you should be able to pull it straight out, but the lip from the vinyl (dash wrapping) creates a "step" that the cluster hangs up on.

I believe I would back one nut off about a half inch, then back the second nut off till the column was resting on the first (loosened) nut.

This is a good tip. Thank You!

[SD455DJ]

PDC, On my Formula, we found we had to totally drop the steering column so we could gently push the 'flat' section of dash directly above the column down to allow the cluster to pull out without scratching the vinyl padding.

Dennis

[PDC]

Gauges went in and all work. Fuel / volt was a bit dicey: one would work and the other wouldn’t. I’d pull the housing, check everything, re-install and then the one that worked didn’t and the one that didn’t did (?). Re-checked everything and both worked, so I stopped messing with it!

Bezel compliments of Randy Combs - looks incredible. Added the brushed silver spoke formula wheel and also got a correct 6-speed pattern shift ball.

All in all, very pleased with how this turned out!

[Bill Hanlon]

Nice! What is the switch to the right of the ejection seat button for?

[PDC]

Originally Posted by Bill Hanlon

Nice! What is the switch to the right of the ejection seat button for?

Heated back glass.

I love the ejector seat button. Makes passengers think.

[4dblnkldude]

Hello, guys I'm reviving an older thread here. Great info! I currently am doing an 81 TA and have a 78 cluster with the 100 mph speedo and want to swap it in the 81. Is this an easier swap than going from 72? Would I need change anything other than the cluster? And who is this Randy Combs guy, does he specialize in these clusters and bezels? Thank you

[bhill86]

I think you would have to re-pin your connector. PM me an email address and I’ll send you something I think will help.