Have a 1988 model with a 115 mph speedometer and the last owner installed whiteface overlays on all the gauges including a 115 mph white speedo. If I put on a 145 or 150 mph overlay, how do I make the speedometer reads correctly? It will show 80 mph when I'm only going 60. Assume this is still a mechanical speedo cable driven off a drive gear in the transmission. Would I just be able to swap out that drive for a different ratio? I guess 25% less teeth? And if so, how do I figure what that is? And would the odometer be off? By 25%?

 

Anything is possible. ...that being said, I don't know that you can do what you're asking. The speedo and mileage are all driven internally with gears like you said. (at least through 89). In theory what you suggested would in fact work. Can it be done? -Not that I know of. It's not like there are kits out there for this. Ultimately, I'm sure SOMEONE out there has the know how, but I imagine even if you found someone, it would cost a good bit. You can buy a new speedometer. There not all over the place, but if you can't find one, give it a few weeks and they'll turn up.

 

The way you fix this is to buy a used cluster with a 140 mph speedo.

GD

 

Camaro IROC only?
1982-89 only?

 

 

Someone else will know - I'm a Firebird guy so I'm not sure on that one. Firebird's went to electronic speedo's pretty early. My 86 TA is 140 mph electronic.....

GD

 

1986.5 to 1989. There are plenty around.

 

For around $200.About what a junkyard pays for the whole car.

 

Welcome to classic car parts. Remember this stuff is 30 years old and not likely to ever be reproduced. Go get an IROC and drive that. It already has the 140 MPH speedo.

These cars aren't ending up in the junk yards as much anymore. Too old.

GD

 

The way you can do it is to have a speedometer with a gauge that is only marked to a certain speed, but the needle will travel past the marked speed. Then you can just print a new label for the face with marks for the rest of the scale. Or you take/send the speedometer to a custom shop and have them recalibrate it for a custom gauge face.

While it might be theoretically possible to rig the speedometer gears in the trans to gain a bit more room on the scale, it's not going to be as accurate, and you can't adjust it very far before you start to run into problems with the integrity of the plastic drive/driven gears.

Anyway you go, it'll probably be easier and faster to just work some overtime, mow lawns, go gay for pay, sell plasma, hold up a Kwik-E-Mart; and just buy a 140mph cluster off Ebay.

 

Fwiw....I just bought a 140 speedo off facebook for $90. Just the speedo, to replace the 85mph speedo on my "extra" gauge cluster. ....just be patient, it'll pop up. Might also contact Hawk's, as they sell a recalibrated 200mph speedo. SOMEONE is doing that work, and might do yours. Still....doubt it'll save you money.

 

You won't do better than this. ....and ya better call soon, because half the guys in this thread probably will!!!
https://dayton.craigslist.org/pts/d/...756052367.html

 

...and if you DO buy it....I'll buy the temp gauge from you. Dead serious. PM me if you do.

 

The motion of the speedo needle is EXACTLY the same, whether it's the dual 85, the 120, or the 140 mph cable-drive units. I.e. if it travels 90° to get from 0 to 60, it will sweep through 90° from 0 to 60, 180° from 0 to 120, and so forth, no matter what the "max" printed on the scale is.

So, if you can get an "overlay", all you have to do is, put the pointer back onto the movement, pointing at 0.

Of greater importance will be, does the trip meter reset stalk interfere with the pointer sweeping through the extra 20 mph.

 

Wish it was that simple. Currently mine is the upper left one. If I install the middle lower overlay the needle will point to 80 when I was doing 60 on the original one.

 

Sofa, I've come to know you for right answers, so I'm assuming I'm missing your point, as is Atikovi, base on his answer. Can you explain that again? -because I disagree with what I think you're saying. The 5 o'clock position of the 85mph is...well....85. Same way on the 145. If he puts the overlay on, the car will be going 85, but would READ 145. I gotta be missing what you're saying.

 

Ignore the tach scales. That's the 2 top right ones.

Next, concentrate on the lower 2 right ones. It's pretty obvious those are the same # of ° of pointer deflection per mph; the far-right just goes farther, i.e. has more marks and #s painted on it.

I don't know what the bottom left one is. Can't think of any of these cars I've ever seen that had that. 4-cyl cars maybe? something that won't ever even get up to 80 mph even down a long steep hill? My 83 came with the dual-pointer POS that only went to 85 but obviously was different from that one. Back in the day, when the national speed limit was 55, it was illegal to put a speedo in a general-public car that indicated past 85. Even though the car would do around 130 if I just held it flat-out for a few miles (paced it next to a slightly later-model Vette).

Same for the top left: not sure what it is.

The 83 dual-pointer thing had the same angular displacement per mph as the 140 or 150. Problem with it is, the trip meter reset stalk comes out of it in a place that prevents the pointer from making even a full 180° sweep... one end of it or the other will hit it.

I wish there were a few more of the available variations pictured there to compare to.

Of course, electronic ones have a completely different discipline. Let's stick strictly with cable-drives here.

 

Sheet mang, all of those gauge faces are from "Fancy Dan" cars. My 83 didn't even have a trip odometer.

There were a bunch of different clusters used. 82-84 were dual needle setups, both full instrument and idiot light versions, V6 and V8 versions, and I'd assume Canadian exports probably were primarily metric. 85&86 were like the later style, but used full taper needles vs stepped needles 87-89. A lot of V6 cars got a super basic idiot light cluster with 85mph speedometer, but full gauges were optional. Pretty sure the 85mph was V6 maybe some base model V8s, 110mph in the middle, and 140 on cars with speed rated tires, ie Irocs with VR Gatorbacks.

It's too bad small digital cameras didn't exist in 1996. Couldnt begin to estimate how many thirdgens I looked at on used car lots, and junkyards in those years. A techgeek buddy of mine had one of the first commercial digital cameras, it was not something convenient to carry. LOL

 

If we just focus on 85-89, I think the vast majority were 85 (lower left) 110 (lower right) and 145 (lower right). ....there was the dealer 160 and 140 too I think, but not from factory. I know my 86 2.8l had an 85 mph, and I know I had it pegged a time or two!!!!!!!

 

I'll have to post up a pick of a 140 and an '87 85 mph cluster. You should be able to see that 80mph is at approximately 12 o'clock (normal to the horizon) on the 145 and near 4 o'clock on the 85.






PM me if you need a 140 speedo. I've got two or three stuck in a box somewhere in the garage. with the T56 swap in my '87 I had to go to an electronic VDO.

 

How about using a 0.750 adapter on the speedometer cable like



Say my 115mph speedo is showing 60. I put on the 150mph overlay and it's now showing 80 at the same speed. This adapter would reduce the cable speed 75% so the needle would now show 60.

 

WIthout doing the math, sure...it'll work in theory. First concern is the with mechanical connections, the more reducers and adapters you run, the more slop and inaccuracies you'll get. Second, and maybe less of a concern, but I just don't like to cobble together fixes. I like to fix things and have it right.

....also keep in mind that your math works perfect at 80/60 mph. ....anything over that (or close) and you're gonna read a little high. Anything lower, you're gonna read a little low. Bah, dude, get you a 145 speedo. That's the right way to fix it. Hit up naf and work out a deal. Gotta pay to play.

 

That is an ACDelco part so GM apparently uses them. This is for a modified car with a built motor and a 115mph speedo just looks silly. Accuracy isn't the price concern, just that it should be better than showing 80 when it's really doing 60. I don't expect to drive it much anyway. PM sent to naf.

 

I recently got the repro temp gage through Rock Auto. Looks good, works well - course I only have about 200 miles with it so far. Would have bought the volt gage too, but they were out of stock.

If you're just looking for a used one, let me know. Got a few in a box. I pieced together parts from three gage clusters to fit the VDO speedo in like I wanted.

 

better pics of the differences in sweep between the 85 and 145

 

There are a lot of after market gauges that are far more accurate -- of course you will be in for a grand or so for a full set and there are gauge pods made for these cars. The firebird gauges have another 90 degrees of sweep past the end of the 120mph scale and the needle will make it all the way to the reset switch ahem *cough cough* so i hear. But do you really care about your speed at that point... you better not be looking at the gauge. Though with the mechanical speedometers you might break them going beyond the scale.

There are also some cheap digital dashes that use GPS for speed vs the trans sensor.

I wounder can you mount a firebird (or other car from the early 90's) speedo into the camaro cluster.

 

the firebird speedo will not go into the camaro cluster because the reset button is in the wrong place.

with firebird speedos going electric in 86 that would otherwise have been an option for an electric speedo for the T56

the integrated high beam light is another problem but resolved by repinning it to one of the below unused idiot lights

 

PM sent about the 145.

 

Are we talking about the mechanical cable-driven speedo for a Camaro/Z28/Iroc, or a Firebird/Trans Am?

I'm not trying to break anyone's potential sale here, but I have a never used in box Export speedo for my 84 Trans Am.
Like Sofa said, back in the day, they could only read to 85 when the national speed limit was 55.
I plan to switch to the Intellitronix digital gauge setup. https://www.intellitronix.com/produc...al-gauge-panel
Cheaper bought on ebay.

 

How much is this adapter/converter?
If it is cheap enough, and since you already have the 150 mph overlay, in theory it should work as you described.

 

agreed the adapter should work. ensure that the fittings match the speedo cable and trans fitting for the 700R4 and that there's room for it between the speedo fitting on the trans and the trans tunnel where the speedo cable turns (in direction, not rotation). might be best if it can be used with the later two-piece speedo cable to avoid interference at the trans tunnel, imo.

Not trying to push a sale.

 

Got under the car for the first time and WOW, never expected that. Welded in tubular chassis stiffeners, 4 inch diameter exhaust, electric exhaust cutout. No wonder this thing sounds like an uncorked Pro Stock car, but I digress. Not much room for an adapter plus the likelihood of scaling error at low speeds, i.e. reading 0 until moving at 5 or 10 mph, has me leaning towards using a 145 speedo. If you or anyone else wants to sell one, PM or email me. atikovi@email.com