V6 Tach Cluster Question

[Roberty]

I have a 1990 Silverado with the moonie gauges and would like to upgrade to the 1991 tach cluster. I found a 1991 tach cluster cheap but it has a 6 cylinder tach. Can I swap it with a 92 up tach easily? What I am talking about is putting a 92 V8 tach in the 1991 cluster and putting the 91 cluster with the new tach in my truck. I know I have to swap 3 wires and all that.

[Roberty]

Anybody???

[Palf70Step]

I missed then when you first posted it. I have not heard of anyone doing it. Did you try and have any luck? I have not dug into my dashes that much so not sure if they are separate gauges and a cluster.

[ChevyTech]

It can be done, but may be more work then you thought.
There are articles you should search for and find about putting a 1992 instrument panel in a older truck. You will need to change the wiring, wiring connectors, and add a DRAC.

There are compatablility issues.

1988-1990 = same
1991 same connector as 1988-1990 but some wires in different positions
Some late model year 1991 trucks had the needle style gauges but no separate DRAC.
1992 – 1994 instrument panel is interchangeable

From my saved notes:
To use a 1991 cluster in a 1988 truck, you have to move B15 to B11, A11 to A10, and A10 to A9 so those will be what's different. Per bowtie44s @ Chevytalk


A V6 tach instrument panel is different then a V8 instrument panel.

For those that want to convert a V6 tach to a V8 (for the 92-94 cluster), remove the tach speedo board and look for C103.

If you lay the board component side up with the connector to the speedo drive motor on the left, there are three capacitor. The charge pump cap (C103) is the smallest of the three just above the thin film resistor pack.

You want to change that cap to .002475uf (2475 pf). The V6 uses a .0033uf (3300pf).

Getting that value requires two caps. A pair of 4700 in series gets you 2350pf which will make the tach read about 300 RPM low at 5000 RPM. That's more actuate than they are normally. The error is less as the RPM goes down. A 2200pf in parallel with a 270pf will get you just about on the money. I selected a pair of 4700pf caps that gave me 2400pf. That's close enough.

If you are a techie, you can check the tach with a signal generator. The frequency is:

(RPM/60) X (NumCyl/2)

Source:
By terryk
http://www.chevytalk.org/threads/sho...rue#Post722625

[speedygonzales]

http://www.dakotadigital.com/index.c...rod/prd911.htm

http://www.summitracing.com/search?S...ord=VHX-88C-PU

Pricey but a lot less headache

[Willie Makeit]

How does one look at a V6 tach cluster and tell the difference between it and a V8 cluster?

[Roberty]

Originally Posted by ChevyTech

It can be done, but may be more work then you thought.
There are articles you should search for and find about putting a 1992 instrument panel in a older truck. You will need to change the wiring, wiring connectors, and add a DRAC.

There are compatablility issues.

1988-1990 = same
1991 same connector as 1988-1990 but some wires in different positions
Some late model year 1991 trucks had the needle style gauges but no separate DRAC.
1992 – 1994 instrument panel is interchangeable

From my saved notes:
To use a 1991 cluster in a 1988 truck, you have to move B15 to B11, A11 to A10, and A10 to A9 so those will be what's different. Per bowtie44s @ Chevytalk


A V6 tach instrument panel is different then a V8 instrument panel.

For those that want to convert a V6 tach to a V8 (for the 92-94 cluster), remove the tach speedo board and look for C103.

If you lay the board component side up with the connector to the speedo drive motor on the left, there are three capacitor. The charge pump cap (C103) is the smallest of the three just above the thin film resistor pack.

You want to change that cap to .002475uf (2475 pf). The V6 uses a .0033uf (3300pf).

Getting that value requires two caps. A pair of 4700 in series gets you 2350pf which will make the tach read about 300 RPM low at 5000 RPM. That's more actuate than they are normally. The error is less as the RPM goes down. A 2200pf in parallel with a 270pf will get you just about on the money. I selected a pair of 4700pf caps that gave me 2400pf. That's close enough.

If you are a techie, you can check the tach with a signal generator. The frequency is:

(RPM/60) X (NumCyl/2)

Thanks for the info ChevyTech but my soldering skills aren't up to the task at hand. Will the 91 V6 tach swap out easily with a later year tach? I was going to buy 2 clusters basically - the 91 V6 cluster and a 92+ V8 tach cluster and swap the 92+ V8 tach into the 91 cluster. Is this easily done? Will the needle come off easily without breaking anything?