Speedometer off...

[RedFish]

If your odo is reading correctly then your speedo will also.

Not true. These are 2 totally different instruments in the one house. The odometer is directly gear driven. So cable rotations, less gears jumping teeth, directly effects odometer. So correct that the speedometer drive gear effects odometer. Odometer correctness can be a good indicator of speedometer drive gear mathematics correctness. At the same time, Speedometer is not direct driven. You could duct tape the speedometer needle at zero and drive the car. Odometer would still operate without change.
And without quoting anothers post, if the magnets did get weaker, the speedometer would run slower, not faster LOL

 

[DrCharles]

if the magnets did get weaker, the speedometer would run slower, not faster LOL

What's funny about a simple mistake?

 

[72Dart6pack]

So it's taken 27 posts to figure out the we still have no idea what final gear he has in his vehicle ? Yikes.

 

[RedFish]

What's funny about a simple mistake?

OK I apologize for the LOL. It wasn't exactly directed at you. When I suggested that the instrument might be the issue here I didn't intend to clutter the thread with instrument details, correct or not.

 

[DartGTDan]

Do you round up or round down on the tire size? I found an online tire size calculator which tells me my tire is 26.7" tall. Wouldn't that be a consideration as well? Enough to worry about?

 

[trapster]

Not true. These are 2 totally different instruments in the one house. The odometer is directly gear driven. So cable rotations, less gears jumping teeth, directly effects odometer. So correct that the speedometer drive gear effects odometer. Odometer correctness can be a good indicator of speedometer drive gear mathematics correctness. At the same time, Speedometer is not direct driven. You could duct tape the speedometer needle at zero and drive the car. Odometer would still operate without change.
And without quoting anothers post, if the magnets did get weaker, the speedometer would run slower, not faster LOL

I guess I should have mentioned that what I was saying was for a working speedometer, if it is slipping or jumping there is no point in trying to make it accurate. but it would be easy enough to compare the ratio of error between what the odo is reading and what the speedo is reading and if they are not the same you have other problems.

 

[69_340_GTS]

Do you round up or round down on the tire size? I found an online tire size calculator which tells me my tire is 26.7" tall. Wouldn't that be a consideration as well? Enough to worry about?

You'll never get it perfect, so use 27" in this case.

 

[CudaFactHackJob]

So your speedometer is about 1/4 too fast. More teeth will slow it down. 33 divided by 4 is about 8. So I'd go with a 40.

 

[str12-340]

I like one thing mentioned early in this thread - get a simple GPS unit that plugs in the cigarette lighter, Garmin makes good ones. It gives you your speed on an ongoing basis and you can even move it from car to car. And it gives you directions so you don't rear end somebody while looking at a map or printed directions (been there, done that). Once you get a better understanding of how far off you are, then you can more accurately find the right speedo gear. if your speedo and cable are 40-50 years old you might just want to correct what it reads and forget the chart, but it might read off inconsistently (20% off at 35 and 40% off at 65) due to wear and tear in the speedo, but the GPS would tell you that.

 

[krazykuda]

It was stamped with the teeth. I have never had one that was stamped and wrong... I can check that too when I am in there.

Make sure that you clock the housing for the gear when you install it... Each mark has a range of teeth that it needs to be set at...

 

[dartfreak75]

Sounds like you don't have 3:23's.

That isn't exact science, are you sure it isn't between 3 1/2 and 3 3/4?

3 3/5 would equal out to be 3.75 or in gear talk 3.73! 3 1/2 turns would be 3.50 or 3.55s so go turn your wheels again and make a good witness mark to get an accurate count. Im willing to bet you have a different gear than you think and that is why your speedo is off.