[mrvette]

OK, the speedo in my '72 here is more or less stock, I had it apart once years ago for a dab of oil and it's been fine....I did a switch to the 200 4r tranny, and so of course had to recal the speedo with the correct tranny driven gear....no sweat....or is it??

So I take vette out on the freeway....wife paces me with pre arranged hand signals....60 is 60, 70 is 70, and so forth....

I get a buddy with his newer pickup 60 is 60 cruise controlled level road...not an issue....

HOW EVER, on way home from beach this morning I am clocking 98 mph and am being passed, and pushed with someone on my tail feathers....

I seriously doubt the 98 mph reading.....

anyone??

OH, the needle is steady....

 

[iburke]

:huh:

 

[turtlevette]

HOW EVER, on way home from beach this morning I am clocking 98 mph and am being passed, and pushed with someone on my tail feathers....

I seriously doubt the 98 mph reading.....

anyone??

OH, the needle is steady....

You don't think people down in FL do over 100 on the hwy.?? They go like hell down there. I wouldn't doubt it a bit.

 

[big2bird]

Well, I can answer this way. When I installed the 700R in the 81, I had to have them add a speed reducer to the drive gear. They did not make gear the right size.
However, I had the speedo refaced to 140 mph. The guy told me the head unit was off 10mph untill 25, then was correct.
Here is the most important. Speedos are not calibrated by the gear set. THE ODOMETER IS. That is what should read correct. 1 mile is 1 mile. Remember the old signs? You set the gears to that, then calibrate the head to match.

 

[Strider]

I use the GPS that I use to train my horse for checking the speedometer. It is extremely accuarate.
If you speedo is accuarate at 6o and 70 it shouldn't change at 98.
Why are you driving that fast in the first place?:laughing: :laughing:

When I installed the 700R I too need a special gear reducer installed in the speedometer cable to get the correct speed.
NO combination of gears will get it right without this reducer. I used a 30% reducer and then geared from there for accuracy

 

[mrvette]

As for driving fast....well what can I say?? but I certinly was NOT ALONE which is why I am posing the question.....is there any really logical way the speedo can be over indicating whem at 60 and 70 i'ts totally correct.....

I even played with a roadside speed sign on a commercial highway up the road and turned around, accelerated up to 40 and set the cruise....40 indicated smooth as hell, confirmed.....

so then with twice the cable speed to the speedo, it HAS to say 80? NO??

I maybe need pull this thing out and take it to a shop....

I know 1000 rpm of the cable is 60 mph....think it's been industry standard for decades allready...

 

[big2bird]

As for driving fast....well what can I say?? but I certinly was NOT ALONE which is why I am posing the question.....is there any really logical way the speedo can be over indicating whem at 60 and 70 i'ts totally correct.....

I even played with a roadside speed sign on a commercial highway up the road and turned around, accelerated up to 40 and set the cruise....40 indicated smooth as hell, confirmed.....

so then with twice the cable speed to the speedo, it HAS to say 80? NO??

I maybe need pull this thing out and take it to a shop....

I know 1000 rpm of the cable is 60 mph....think it's been industry standard for decades allready...

I would. Gene, the guy who does my cars has been doing it so long, he had spare parts for my 23 Ford. He taught me when I was a kid. He takes the car out on the street. He has a 1/10 mile marked by streetlights he knows of on a side street. He pulls the cable off the head, and counts the turns in 1/10 mile while idling down the street., then multiplys by 10. This gives him a base to correct the odometer from. He then spins the head in a machine to set it to standard .