junkyard speedometer going crazy

[irowiki]

So I got a junkyard sr5 cluster for pokey, installed it, and the clock works!

Unfortunately the speedometer is wonky. It records miles just fine on the odo/tripmeter, but the speed reading is way fast. From 5-30mph too fast.

I tested the old cluster and a third cluster (someone else's) and they work fine.

Sadly the old cluster has no clock and the trip reset is broken.

Any ideas or anything I can fiddle with?

[Gottolovem]

Maby some light oil 2 or 3 drops in the back?

Is it consistently too fast or hopping around If it's consistent you could install it without the plastic screen then start driving down the road with a smart phone spedo going pull the needle pointer off then stick it back on at the speed the phone says your going.
I had to do that on a caddy and it worked out ok it was within 3 miles per hour.

[irowiki]

Well we just went for a drive to test for sure based off RPM, unfortunately it is 5 MPH off at low speeds, and 20+ MPH at high speeds.

10 MPH shows 15, and going 70 shows 90 (pegged).

I'm guessing it is toast?

[Gottolovem]

What a bummer you want me to try and find another i have the one i glued the odometer in?
Rusty has a good one but i'm still undecided on what to do with that car.
It will be hard to sell and i don't need another driver.
It works but wrong speed Sounds like the wrong gear ratio somehow?

[irowiki]

Ah, does the one you glued in work?

Eventually I'll end up with a spare after parting out "Snap" but that might be a while.

I'm going to take the current one apart and mess with it since I have nothing to lose. I have a DLX cluster somewhere I could try too...

[Gottolovem]

It came from my parts car that i have never driven so i'm not sure.
But the car came to me because of bad tranny

[irowiki]

Interesting, I guess factory cruise cars had a special cluster:

MPH (head only), SW, cruise control, tachometer (SR5)
MPH (head only), SW, cruise control, w/o tachometer
MPH (head only), SW, w/o cruise control; tachometer (SR5)
MPH (head only), SW, w/o cruise control; w/o tachometer

[Gottolovem]

what's the SW stand for?

[irowiki]

Station Wagon, I was searching on car-part for 87, it splits second gen into "SW" and third gen into "lftback/sedan".


If I search for 86 this is the result:

KPH (head only), tachometer (SR5)
KPH (head only), w/o tachometer
MPH (head only), tachometer (SR5)
MPH (head only), w/o tachometer; cruise control
MPH (head only), w/o tachometer; w/o cruise control

[Gottolovem]

Rusty has factory cruse and i don't think there is a difference?
Come to think of it my 87 auto had cruse stuff on it to but i figured it was someones Frankenstein job and took it all off all autos are dx models.
Do you think that "head only" could be a different gear ratio

[irowiki]

Not sure what the head only thing means.

Only thing I can think of is maybe an extra sensor in the cluster?

[Petros]

I think it has a speed sensor for the cruise control. I have notices when it is really cold my own speedo with read high, and sometimes peg due to internal contact. it works with a magnate that spins next to a plate, that is attached to the needle. when the parts where there is a slight amount of slope and I suspect that it might make contact when very cold due to change in size of the parts. I can also hear slight rhythmic scraping sound cumming from it.

If yours is too high at all speeds and all temperatures, than it might have the wrong ratio drive. the auto trans, manual trans, and '83-84, and '85 and newer all have different ring and pinion ratios in the diffs, and use a different speedo drive gear too. You might go back to the wrecking yard and see if can get the drive gear out of the trans and install it in your trans, that might fix the speedo error. hopefully the manual trans and auto trans use the same type of speedo drive gear so it can just be swapped out.

[irowiki]

So I fixed it!

I ended up swapping the little brass/copper colored piece that reads the speed from my bad cluster. Essentially I converted a 85 MPH speedo to a 110 MPH one.

A picture of the part in question can be provided if needed.

[Gottolovem]

Sweet thats great news

[marlinh]

A picture would be great Paul.