Speedometer Head from a 89 to an 88

[jpitte65]

I need a speedometer head for my 88 k5 blazer. i have someone that can get me one from an 89 with a tripometer i know i would need to drill a hole for the tripometer reset but would everything else still match up correctly i do notice that the high beam has one indicator light hole while the one i have in my truck now has two on either side of the picture will that make a difference he are some pics of the 89 speedo no current pics of mine since i havent taken it out yet

 

[4X4HIGH]

You're saying your speedo head has 2 holes in it for a hi beam indicator (and possibly something else)?

 

[jeff in co]

Just take the tumbler out of your existing one (mileage) and drop it into the new one. Everything should work out great to use as much of one speedo as possible. No drilling or anything. I think if you start drilling into the face, it will look like a hack job.

Just note where the indicator is located so you place it back in the same spot when you re-assemble it back together.

 

[4X4HIGH]

His question has nothing to do with the odometer or trip odometer. He is saying that his 88 speedo has 2 holes for indicator lights at the top whereas mine only has 1 hole for the hi beam indicator (This is a pic of my speedo he's looking to buy).

 

[jeff in co]

His question has nothing to do with the odometer or trip odometer. He is saying that his 88 speedo has 2 holes for indicator lights at the top whereas mine only has 1 hole for the hi beam indicator (This is a pic of my speedo he's looking to buy).

I assumed he wanted to keep his mileage odometer but if he doesn't care, then yes, your 89' speedo will work with his 88' and will bolt straight in. Where is he wanting or suggesting to drill the hole? In the clear, plastic gauge cover (I assume) or the gauge face?

The two high beam holes vs. one.......simply asthetics.

 

[jpitte65]

yeah the one that is in my truck now has to holes on each side of the 55 mile mark i am assuming it is just a bulb behind it that shines through both and i know i would have to drill a hole in the plastic lense to get the tripometer reset through but everything else should be the same right

 

[4X4HIGH]

It will swap right into your cluster, just drill the hole for the tripometer and you're done. I could have swore though that the tripometer started before 1989. Maybe you have an earlier cluster in your truck? Your speedo is 0-85 mph isn't it?

 

[4xcrazy]

Or just swap out the clear lens cover too, they only screw in place...

 

[jpitte65]

mine actually goes up to 100 i think the guy i bought it from thought by changing the speedo he could correct the speedometer reading. he said it was from an 87. he broke something putting it in. i have the speedo gears to change to correct it. so just need a head to read it

 

[jpitte65]

i will take some pictures of the front of mine in the truck and post them on this thread

 

[4X4HIGH]

Since the speedo goes 0-100 mph it is definately an earlier speedo, all of the TBI stuff for a fact is only 0-85 mph. I don't think you can swap your odometer from that speedo to the newer style (the correct one for your vehicle). Also, ALL TBI trucks from 87-89 used an optic eye VSS that attaches to the back of the speedo and obviously since someone swapped in an earlier speedo you no longer have a working VSS.

 

[4xcrazy]

gonna have to argue on that one, sorry, the VSS stuff was in '90 - '91. My '89 still uses a speedo cable setup. nothing electronic on there at all except the wiring and printed circuit for the gauges.

 

[4X4HIGH]

gonna have to argue on that one, sorry, the VSS stuff was in '90 - '91. My '89 still uses a speedo cable setup. nothing electronic on there at all except the wiring and printed circuit for the gauges.

Sorry but starting with TBI in 1987-1989 GM used what is called an optic head VSS which attached to the back of the speedo (little green box with three wires going to the sensor which reads the 2 spnning poles around the magnet for the speedo) and the speedo is CABLE driven, then starting in 1990 GM went with the DRAC VSS style with an electric speedo.

I am 200% correct with that statement.

 

[79rustyk10]

Sorry but starting with TBI in 1987-1989 GM used what is called an optic head VSS which attached to the back of the speedo (little green box with three wires going to the sensor which reads the 2 spnning poles around the magnet for the speedo) and the speedo is CABLE driven, then starting in 1990 GM went with the DRAC VSS style with an electric speedo.

I am 200% correct with that statement.

What he said, when I did my TBI conversion I FUBARed the optical eye thingy and had to find another one. I also put the 100mph speedo face on the 88 speedo guts to keep everything matching, but the odometer is a little further up behind the face and it doesnt look right.

 

[Big Ray]

Sorry but starting with TBI in 1987-1989 GM used what is called an optic head VSS which attached to the back of the speedo (little green box with three wires going to the sensor which reads the 2 spnning poles around the magnet for the speedo) and the speedo is CABLE driven, then starting in 1990 GM went with the DRAC VSS style with an electric speedo.

I am 200% correct with that statement.

my 86 (carb) and the ex's 89 (tbi) have the green box...I'm pretty sure it was just for cruise control....both were/are cable driven speedos

 

[4X4HIGH]

my 86 (carb) and the ex's 89 (tbi) have the green box...I'm pretty sure it was just for cruise control....both were/are cable driven speedos

On the TBI vehicles the optic head was used for the ECM and the cruise control.

The Brown wire goes to the ECM A10 terminal and the Yellow wire goes to the cruise control.

 

[79rustyk10]

Would there be a problem if I replaced a green one with a yellow one? I got one out of a truck at a JY and it was yellow instead of the green I normally see on here.

I havent been able to figure why it runs like ****, but havent done anything with the truck since last summer due to college killing any spare money, just got to thinking maybe thats why?

 

[4X4HIGH]

Would there be a problem if I replaced a green one with a yellow one? I got one out of a truck at a JY and it was yellow instead of the green I normally see on here.

I havent been able to figure why it runs like ****, but havent done anything with the truck since last summer due to college killing any spare money, just got to thinking maybe thats why?

I've never seen a Yellow one before, what did you get it from? I would say that you should probably just find the green one that came in out trucks so you know there isn't a problem with it being wrong. I have one in the garage I could check to see if there are any numbers on it that you could check against your yellow one though.

 

[79rustyk10]

Thanks for the offer, Ill just go find a green one, I know of a few 80's TBI burbs in yards right now. the yellow one came out of an 80's carbed 3/4 or one ton from what I remember. probably only serves the CC or something Im thinking now.

 

[4xcrazy]

Guess mine is all fubar'd then, nothing like you describe on the back of mine, and i've had it out several times now. oh, and it's all stock.... oh well...

I have seen the box you are describing on other gauge assemblies I have picked up through the years, mine isn't like that, just a cable going into the back.