Adding a factory Tach

[doc70sub]

Hey Guys,
I'm looking to swap the tach guage cluster from my '79 K-5 to my '82 K-10....its my understanding that the '78-'84 models are pretty much a plug-in-play swap....is this correct?
Thanks!
Doc

 

[k5guyva]

Everything I've seen is a big yes. I've swapped parts from my 82 to 86 with no problems. Since all the parts interchange stuff I've seen lists the 79, you should be ok.

 

[Steve_87K5]

I put a '79 tach in an '87 cluster. Some of the plastic parts
of the '87 cluster that hold the tach needed to be ground with a mototool a bit. Not a bad job. Exterior appearance is unchanged. Electrically, it is PNP. The tach lead does radiate ignition noise RF to the radio if you listen to AM band.

 

[skratch]

So if I understand this correctly, the truck came from the factory already set up for the tach, all I need to do is locate a cluster that has the factory tach and small fuel gauge. Then it will plug in and I won't have to do any custom wiring at all to make it operate properly. /forums/images/graemlins/confused.gif

If this correct then does anybody have one of these clusters for sale?

 

[b55baron]

I put a factory tach in my '89 when it was new. Back then you could buy all the parts new from a GM dealer. As I recall, we replaced the cluster housing, printed circuit, and a circuit board along with the gas gauge. We had to cut a piece off the original housing and epoxy it to the replacement so that the cruise control would work, but otherwise it was plug and play. The only "wiring" we had to do was fish the tach lead thru the firewall to the distributor and plug it in.

 

[bpiccioni]

I wonder if you could go into a little more detail on what part of the cluster affected your cruise control? I just replaced my busted cruise/turn signal lever in my 87 /forums/images/graemlins/burb.gif w/ a new one, but still dont have cruise - your information could be VERY useful in troubleshooting my cruise control problem. Thanks!

 

[Steve_87K5]

No, I took out the large fuel ga and put the tach in there. I put in: tach ('79-'87) $209.00 GM 25054251. Small fuel ga is available from same yr series. You take out that wonderful clock though. I removed the 4x4 idiot light and put digital fuel ga in that window. LMC still sells this tach and sm fuel ga AFIK. Check with GM, their parts system will sometimes locate parts at various locations. That price was a 1993 price from Mr Goodwrench.
The tach has 3 connections: +12VDC from ign/switched, GND and TACH signal from HEI. Don't mess with the printed wiring.
Cruise is not involved, but in ref to your problem, I'd check the electronic module. This is the usual culprit, not the stalk (check stalk switches with VOM). HTH

 

[b55baron]

I don't remember offhand why we had to use the part off the original cluster housing for the cruise control. I'll check with my buddy who helped put it in. He worked as a mechanic for one of the dealerships at the time and got me all the parts. He put tachs in 3 or 4 other trucks, including his '89 Suburban and was the one who knew the trick about the cruise control. We're going to a car show this weekend and I'll ask him.

 

[b55baron]

I talked with my buddy over the week-end. He couldn't remember the details either. It might have to do with the fuel injected trucks not having the transducer for the cruise control under the hood like the carbureted trucks did, but I'm not sure.

You might try looking at the back of the cluster housing that came out of your truck and comparing it to the one that the tach came out of to see if there are differences.