Very Slight Difference in 68 1600 Speedos and 69 2002

[jwcurry]

I was looking through the parts collection tonight particularly, at the instrument gauge pod and even more particularly, at the difference between 1968 speedos and 1969 speedos. I'm assuming the 68 set-ups must have been on only 1600's or very early 1969 02's coming off the line.

The early 2002 speedos, have red lines next to 30-55-80 MPH.

The 68 speedos have:

1 red line next to 25 MPH

2 red lines between 45-50 MPH

3 red lines between 70-75 MPH

Pretty neat little difference. I think I like the increasing red line effect a bit better. In my opinion only, the gauges got a little more chintzy looking as the model years passed by.

Jerry

Jerry

[blue7500]

1600s had shorter diffs, 4.11:1 instead of 3.64:1 found in pretty much every 2002.

[jwcurry]

Yes, I was thinking about the different diffs.....and if that was the reason the speedo face was redesigned.

What I think you also might be saying is the 1600 speedo are probably calibrated or geared differently than the 2002 speedos. So, they aren't really interchangeable and they would be off by some factor if one were to install an early speedo in a later console.

JErry

[blue7500]

Right, for whatever reason the speedometers are internally calibrated according to the differential. That means the speedo drive gear in the transmission is also different.

But yeah it's always fun finding all the little tiny differences between early and later cars.

[ray_]

Speedos were calibrated to diffs, not consoles.

;-)

Cheers,

Ray

Yes, I was thinking about the different diffs.....and if that was the reason the speedo face was redesigned.

What I think you also might be saying is the 1600 speedo are probably calibrated or geared differently than the 2002 speedos. So, they aren't really interchangeable and they would be off by some factor if one were to install an early speedo in a later console.

JErry

[Delia]

Speedos were calibrated to diffs, not consoles.

;-)

Cheers,

Ray

Hmmm...

So if my '74tii has a five speed, 3.64 lsd and 14" wheels with 195/60s, all I need to do is install an early speedometer to get a "corrected" speedo reading whilst cruising the Bay Area?

If so, "which" early speedometer?

Please don't make me do math in my head.

Delia

[jimk]

The speedo calibration is based on the number of speedo cable turns in a mile. So for 60mph, the number stamped on the back following the W is the rpm of the speedo cable at 60mph or in one mile. The speedo gear in the trans are all 2.5:1. So an easy way is to take the engine rpm while in direct drive (4th) 60 mph, divide by 2.5 and go shopping or compute the wheel turns in a mile, multiply by the final drive ratio, divide by 2.5 and then go shopping.

[tjones02]

All of my '66, '67 and early '68 1600-2 speedos have the increasing red lines... I believe it was due to 1600's not having tachometers and thus needing the shift points marked of on the speedometer, hence...

The 68 speedos have:

1 red line next to 25 MPH

2 red lines between 45-50 MPH

3 red lines between 70-75 MPH

... the lines mark the shift points out of each gear. It's a neat little trivia bit. and something I try to keep original when I replace broken speedos.

I picked up a 6 volt tach for my '66 and am looking for period VDO gauges including a clock. I know, neigh impossible but I've got time on my hands.

[ray_]

You seem to be making the scary assumption that 30 year old speedos retain their accuracy. ;-)

I still have an open order for a calibrated speedo. I was told the process was to push the car 528 feet while counting cable revolutions and then supply the data to N Hollywood Speedometer.

Your Miles May Vary!

Cheers,

Ray

Speedos were calibrated to diffs, not consoles.

;-)

Cheers,

Ray

Hmmm...

So if my '74tii has a five speed, 3.64 lsd and 14" wheels with 195/60s, all I need to do is install an early speedometer to get a "corrected" speedo reading whilst cruising the Bay Area?

If so, "which" early speedometer?

Please don't make me do math in my head.

Delia

[ingraham]

... which is probably what your '74 had originally. The speedo and odo will run slightly fast because 195/60-14 tires are slightly smaller than the original 165SR13 tires.

Don't expect much accuracy from 2002 speedometers. If you get +/- 3 MPH, you're lucky. If you need extreme accuracy, use a GPS receiver.

[Harv]

The speedo calibration is based on the number of speedo cable turns in a mile. So for 60mph, the number stamped on the back following the W is the rpm of the speedo cable at 60mph or in one mile. The speedo gear in the trans are all 2.5:1. So an easy way is to take the engine rpm while in direct drive (4th) 60 mph, divide by 2.5 and go shopping or compute the wheel turns in a mile, multiply by the final drive ratio, divide by 2.5 and then go shopping.

BIG GOLD STAR FOR JIM!

John