Adding tach

[gric_az]

Wasup guys. I've been wanting to add a tach to my 88 k2500. I've read other website info of people putting gauges from newer trucks in with no problem. Do non tach trucks already have the wiring necessary behind the gauge? Or is new wires needed.

 

[skylark]

Wasup guys. I've been wanting to add a tach to my 88 k2500. I've read other website info of people putting gauges from newer trucks in with no problem. Do non tach trucks already have the wiring necessary behind the gauge? Or is new wires needed.

New wiring is needed either way with an 88. You can put in a cluster from a 92 - 94 with some wiring work. Or you can install an aftermarket tach. The only wiring that is already there so to speak either way is directly off the coil itself. There is an open terminal about 4 in from the coil on the negative side. That is the one you need to use for the tach.

 

[gric_az]

Thanks for the info. Open terminal by coil? I don't understand

 

[7thdarkangel]

Its a spade connector that's not plugged into anything. Locate the ignition coil and you will see a lead that not plugged in. That's where you get your tach signal from

 

[skylark]

Thanks for the info. Open terminal by coil? I don't understand

Exactly what @7thdarkangel said.

 

[7thdarkangel]

If for what ever reason you have an hei distributor(coil in the cap), the tach signal is labeled on the cap where the wires are plugged in.

 

[DerekTheGreat]

What skylark and 7th said.

I've done this to both trucks we had. Got lucky with junkyards as the drop in cluster is supposedly unobtainium. That cluster was a mid year thing for 1991 model year trucks and drops right in place of the old slice-o-pie garbage. You'll want that cluster as it's got a built in DRAC module for speed and a lot easier to integrate in place of the old cluster. Here's a good write up on what you need to do, mostly it's just adding a wire for the tach and moving a few others around and you're done:
http://67-72chevytrucks.com/vboard/showthread.php?t=313815

When you find the unobtainium cluster, make note of the tire size & rear ratio combination it has either from the RPO stickers or door tag and then you can see if the cluster is ready to go for you or needs to be recalibrated. I got lucky both times in that the cluster I pulled was exactly what I needed.

 

[gric_az]

That's alot of info and I appreciate it! I think I'll just add an external tach.

 

[Denny 1991]

I changed to the mid-year cluster and the tach needed no additional wiring to operate properly.