Adding a tach question

[quaddriver]

1990 R2500. No tach, large fuel gauge in its place.

I can get a repro tach. It appears I also need to replace the PC foil as well? (and get a small fuel gauge)

I found sources for all parts (LMC) but the fuel gauge.

So riddle me this, is it true that if you did NOT have the tach, then the PC foil is different and there was not a universal wiring scheme because a gauge function has moved?

Any caveats before I order parts?

 

[J Knight]

The lmc tach and printed circuit are for an original tach gauge cluster, the fuel gauge wont fit standard gauge or base model clusters without clever modification.

If you want a simple factory looking tach, try a gm sports salvage tach like this.
Follow thread from page 8 to about page 11.

http://www.gmsquarebody.com/forum/showthread.php?t=1647&page=8

 

[RetroC10Sport]

There was a tach cluster in trucks with an electronic speedo but only like 50 were made.

I am with J Knight though. The Sports Salvage tach is pretty sweet but you lose two warning lamps.

 

[J Knight]

True Retro, I lost the seat belt warning light and the brake warning light.

 

[RetroC10Sport]

Two you generally do not want to lose if you have inspections. But I am sure they can replaced and used under the speedo with a little repinning of the connector.

 

[J Knight]

Two you generally do not want to lose if you have inspections. But I am sure they can replaced and used under the speedo with a little repinning of the connector.

I got antique plates, no inspection required.

 

[RetroC10Sport]

Yes, but I know PA (where the OP is from) can be strict.

 

[Old77]

Just bookmarked the gauge that @J Knight bought in that link he posted in the other thread I'd forgotten all about that and would be awesome in my 87!!!

 

[quaddriver]

The lmc tach and printed circuit are for an original tach gauge cluster, the fuel gauge wont fit standard gauge or base model clusters without clever modification.

If you want a simple factory looking tach, try a gm sports salvage tach like this.
Follow thread from page 8 to about page 11.

http://www.gmsquarebody.com/forum/showthread.php?t=1647&page=8

Ok I didnt fully understand that, my truck (90) has speedo, large fuel, and 3 gauges to the left, with the lower left empty.

If I pull the cluster and replace the PC foil with the LMC pc foil, everything would still work, Id have my lights, but now my big fuel gauge would either not work at all or go crazy?

So next I would pull the big fuel, replace with the tach (LMC makes 3, only 1 of which fits the 88-91) and it would work, lights would still work but I have no fuel.

There appears to be no aftermarket small fuel gauge for the lower left hole, so I would have to boneyard search for that.

IS all of that correct?

I talked to a guy at carlisle last month who specializes in square subs and he gets 600 for a reman cluster package with everything, with the electronic speedo - which he says the 90 454/400 already has. I have not actually taken the time to check my speedo drive, but is he correct?

thanks...

 

[J Knight]

The plastic case (cluster housing)for a tach is different than a cluster housing equipped with gauges(large fuel and small gauges/clock) and is also different that a base cluster housing with warning lights.

You also need to verify that your pin out on the cluster plug is correct and compatible with the new printed circuit.

 

[quaddriver]

thats sad if true...they could have taken a lesson or two from ford....

back to the drawing board

edited to add: for $60 lmc sells a new cluster backing housing in the blue greenish plastic for models with the tach. If everything else is the same, save the 'bucket' the tach installs into...would this solve my problem?

For that matter, since I might be doing wiring anyways, I can get any small fuel gauge from them for the lower left.

so if I order the 'with tach' backing plate for 88, the 90/91 PC foil, and the 90 tach...are we there? (some assembly required of course)

edited to add again...

playing detective and using the LMC catalog (which I do not consider to in no way be the holy grail - most of GMs engineering and parts info did not make it to the web and was abandoned) we find:

LMC part 38-8100 aka 'cluster backing plate' for trucks with gauges but no tach, is the same in grouping 81-88 and 89-91 on two pages of the catalog. That tells me that while the gauges may be different, the mount points are not. since adding a tach to any of those years moved the fuel gauge we can assume that part 38-8101 (trucks with gauges and tach) will mount all the gauges not moving position and all of the bulbs will work etc.

So that opens the door to let me get tach 36-1882, 2nd design 89-91 which would apparently look correct for my dash

It also appears that I can get any small fuel gauge from either LMC or a boneyard.

as for the pc foils. it appears that if you have gauges and no tach, the foil is the same 81-91, but with a tach only goes to 87. That in itself is telling as 1988 was the new design on the pickups (but not SUVs) and I know (from the other full size chevy site) that the 88-99 dash and crap fits with little to no modification inside an 80s square, including the 90/91 Sub. This means that GM likely worked on standardizing the wiring harness so it would probably not fit.

But all is not lost, its easy to modify the foil, jumper, cutting etc. I have a process where I make mechanical and electrical connections for longevity so it would not be hard to get a fuel gauge, make a harness usign a molex plug, and wiring the tach into the harness (from what I have found, the tach signal is present in the cab, all models after 1988 - gauges be damned.)

So this could be doable. opinions on my research?

 

[quaddriver]

Yes, but I know PA (where the OP is from) can be strict.

Actually, I hold my PA inspection license and only the other guys can be pricks!

seriously tho, there is nothing in the inspection procedure that names the light OTHER than, if it is on, the vehicle has to have an ABS system that reverts to normal operation. You are clued into this by the light being on (and perhaps the ABS light as well) but it stops just fine.

sooooooo, I guess if you didnt have the light, it could never be on....

(we do have to check that turn signal, 4 way and high beam indicators work....)

however, what we check for it not all of the PA MVC. I maintain that full compliance it impossible - if the trooper wants your azz on an equipment vio, he will get it.

officer whatever no longer has to bust your taillight to get ya...he has written means.

true fact: we can fail a brand new 80's/90s S truck or c/k on front end...the inherent play in that goofy idler/pitman setup violates the movement, even tho its fine, so your QAO instructs you to use common sense and not be a jerk.

 

[MadOgre]

The factory tach bezel housing is just the non tach with an opening behind the tach. So it would be very easy to take a non tach housing and dremmel an opening behind the large fuel gauge. It is simply there so that you can access the pins on the back of the tach as the tach does not connect to the circuit board.

So cut an opening, install the small fuel gauge where the clock would be and install the tach circuit board.

You still need the Tach circuit board, the Tach and the small fuel gauge.

Just trying to clarify about the factory tach bezel housing vs the non tach housing.

 

[J Knight]

The bottom pic is what a tach housing looks like.

 

[quaddriver]

your picture = 1024 words.

It appears that the tach-able housing ALSO includes mount points for the lower left gauge (needed) and removes some weird circle.

the blue looks an inch or two wider in the pic - its just a perspective issue from the pic right?