Speedometer woes....

[Tigger]

I just got home from a 1500 mile road trip in my 86. I put 3.55's in it about 5-6 years ago. At that time, I did the speedo gear calculator thing and figured out what gear I needed. If I remember correctly, they did not make the exact one I needed and I ended up using the gear that was 2-3 MPH slower as my wife had a lead foot and that would be safer than being fast. I checked it out on one of those radar things and at 35 it was 2-3 miles slower so I left it.

I went up to Idaho this past weekend. Speed limit is 80 there After a while doing 80-90mph the speedometer started making a bunch of noise, rattling and such and the needled would bounce around. Slowing back down the noise and bouncing would go away. Low speeds, like city driving it was back to normal.

Yesterday on the way home, I passed through a couple construction zones and they had a radar thing going and it said I was doing 10 MPH slower than what my speedometer showed. I had my son load a GPS speedometer app on his phone and we checked it and sure enough I was about 10MPH slower at highway speeds. At speeds 0-25 the speedometer is accurate. 35MPH, the speedometer is 2-3 slower. At 55 it is about 5mph slower. 60-80, 10 MPH slower

I am thinking my speedometer is all messed up. With the speedo gear I have installed; the speedometer should be 2-3 MPH slow across the board and not change with the vehicle speed. Is that a correct statement? I always suspected something was not right at highway speeds but didn't think It was that much off.

Did Saleen use a BBK 170 MPH speedometer or did they modify the original speedometer?

Any insight would be appreciated

Thanks

[wraithracing]

Unfortunately the OEM speedometer do wear out over time. Sometimes changing the driven gear in the transmission can cause additional strain on the speedometer depending on what rear gears you are running.

It is possible that the driven gear in the transmission may be getting worn out as often happens if they were aftermarket since the plastic was not as strong as OEM. So I would start there. Otherwise you likely either need to replace your speedometer or have it rebuilt.

The Saleen speedometers were OEM speedometers that were modified to run at 1/2 speed from what I have been told. That is reason they were 170MPH, OEM 85MPH X 2 = 170 MPH. That is the same that BBK does with their modified speedometers too, but I don't believe BBK existed when the first Saleen Mustangs hit the market, so I doubt they produced the speedometers for Saleen.

[gmatt]

I believe that when they are 'off', it's by a percentage not a set amount. So, the faster you go, the greater the discrepancy.

[85GTGuy]

With the speedo gear I have installed; the speedometer should be 2-3 MPH slow across the board and not change with the vehicle speed. Is that a correct statement?

No, that is not correct. (See below)

I believe that when they are 'off', it's by a percentage not a set amount. So, the faster you go, the greater the discrepancy.

Exactly.

For example, since you determined that it was 2-3 mph off at 35 mph, then it should be 4-6 mph off at 70 mph (ignoring the built-in tolerance that the speedometer itself is going to have on it's own.... which I'd always heard was +/- 5%; ie, a 50 mph indicated speed could be anywhere from 47.5 to 52.5 mph actual velocity).

[Tigger]

Thanks for the insight. It makes sense. Trey, I used an OEM speedo gear. I have a box of all different ones from cars I have parted throughout the years. I remember having to cut of the snout to make it fit. I think there is a difference between automatic cars and manual transmission cars.

My car has 213K on it currently so it does not surprise me if my speedometer is worn. It makes sense because it is real noisy at high speeds.

Any idea who can service it or should I try and find someone local to do it?

[gmatt]

My car has 213K on it currently so it does not surprise me if my speedometer is worn. It makes sense because it is real noisy at high speeds.

Any idea who can service it or should I try and find someone local to do it?

There is also the possibility that the noise is coming from a worn(213k miles) speedo cable. It could be binding, causing the needle to jump around especially at higher speeds. Not saying that's it, just a possibility to consider.

[mongos82ttop]

Tigger,

From what i was told by a Saleen sales associate back in the early 90"s, that Stanton Speedo in California, was the company that modified the speedometers for Steve Saleen.

I had built a replica 1984 Saleen Mustang back then and sent my speedometer to them to be recalibrated. They knew exactly what to do to recalibrate it to read exactly half of the original speed.

You might could check to see if they are still in business and they should be able to refurbish your speedometer if needed.

Just an idea for you.

[85GTGuy]

You might could check to see if they are still in business and they should be able to refurbish your speedometer if needed.

Does not appear to be in business anymore.... looks to be an auto stereo shop in that building now.

[Tigger]

There is also the possibility that the noise is coming from a worn(213k miles) speedo cable. It could be binding, causing the needle to jump around especially at higher speeds. Not saying that's it, just a possibility to consider.

Speedo cable is not original. The cable that was on the car when I bought it was melted from the exhaust because It was super long. I think it was aftermarket. I put a used Ford one off one of my Pinto parts cars I had at the time. It is a tad on the short side but it works just fine. I just have to loosen the frame rail hold down before I pull the cluster as there is not a lot of slack.

I cleaned and lubricated it before I installed it but that was 15 years ago and ~53K miles. I may take it out and lubricate it again and see if that helps.

[85GTGuy]

I may take it out and lubricate it again and see if that helps.

I think that's a good next step. Like I recommended on the other speedo cable thread, I'd use a graphite lube.

http://vb.foureyedpride.com/showthre...=1#post1954178

[Tigger]

Thanks for the help guys

[Bentley]

There used to be a really good speedometer shop in Downtown Portland, not sure if they are there anymore... We took many speedo's there when I lived in Eugene..... Can't remember their name or address... Portland is like NYC when you come from Eugene..... LOL

[Tigger]

There used to be a really good speedometer shop in Downtown Portland, not sure if they are there anymore... We took many speedo's there when I lived in Eugene..... Can't remember their name or address... Portland is like NYC when you come from Eugene..... LOL

I know the place you are talking about. It was right off the 405 and Everett I believe. My grandpa had something repaired there when I was in High School. I do not think it is there anymore, I think it is a brew pub now. That whole area has changed in the last 20 years.

[4-barrel Mike]

Did you try https://www.speedometerserviceportland.com/ ?

Or https://www.abbottinstrumentrestoration.com/ ?

Mike

[Tigger]

Did you try https://www.speedometerserviceportland.com/ ?

Or https://www.abbottinstrumentrestoration.com/ ?

Mike

Mike, unfortunately I have not had time to fool with the car lately. It is still all dirty with the spare tire still installed. Work is busy, my youngest son is playing sports so not a lot of free time. Thanks for the links though.

[4-barrel Mike]

FWIW, the last time I went to the speedometer shop in inner NW Portland, they had apparently recently moved. Sign on the door directed me to their new location just off of Front Ave, about half way to the St Johns Bridge.

Mike